Potatoes and tomatoes plant


Crop Rotation – The Four Year Crop Rotation Plan

As with the three year crop rotations and five year crop rotations, we divide our plot up after allowing for the permanent beds of comfrey, asparagus and rhubarb etc. In this case into four beds or areas.

We start the preceding winter by adding manure to the first plot, which will have potatoes planted in it. The plot is at the far end from the lime and manure acidifies the soil so the pH should be good for potatoes.

The second plot which had the potatoes the year before, will be limed heavily to take the pH up to neutral and the other plots will have compost as available.

On heavy clay soils you will probably be digging over each winter to allow the frost’s freezing and thawing action to break up the soil. With other soils it would be a good idea to sow an over-wintering green manure crop to hold nutrients that would be washed away in the rain.

The green manure can be dug into the soil in the spring to release those nutrients and improve the soil’s humus level with the organic matter. On really light soils a green manure is vital to build good condition and adding the manure or the lime in early spring after digging in the green manure is suggested.

The other two plots can be split with the legumes, beans and peas taking one plot and the onion family taking the other.

Year 1 Plot 1
Potatoes followed by lime

Plot 2
Legumes (Beans) followed by additional manure

Plot 3
Brassicas & Other Crops (Lime around brassicas at planting time)

Plot 4
Onions & Roots followed by heavy manuring

Year 2 Plot 1
Legumes (Beans) followed by additional manure

Plot 2
Brassicas & Other Crops (Lime around brassicas at planting time)

Plot 3
Onions & Roots followed by heavy manuring

Plot 4
Potatoes followed by lime

Year 3 Plot 1
Brassicas & Other Crops (Lime around brassicas at planting time)

Plot 2
Onions & Roots followed by heavy manuring

Plot 3
Potatoes followed by lime

Plot 4
Legumes (Beans) followed by additional manure

Year 4 Plot 1
Onions & Roots followed by heavy manuring

Plot 2
Potatoes followed by lime

Plot 3
Legumes (Beans) followed by additional manure

Plot 4
Brassicas & Other Crops (Lime around brassicas at planting time)

Sweetcorn and squashes, pumpkins tend to take up quite a bit of space and like rich soil so I would fit these in with both legumes and brassicas.

If you have enough land that you are not pushing for maximum crops and you don’t have clubroot to worry about, follow your potatoes with a green manure of mustard. The use of mustard as a green manure after the early potatoes hardens the cysts that contains the next generation of potato eelworm so preventing them from hatching.

Since the bean family tend to fix nitrogen rather than exhaust it, these go well before the brassicas. L D Hills suggested that the bean family should follow the lime with the brassicas on the second year after liming.

Since most of the expert brassica growers suggest liming immediately before brassicas, you could go lime, legume, additional lime, brassica if you wish.

The onions and the root crops share the last bed in the rotation.

Permanently Sited Crops

  • Rhubarb
  • Jerusalem Artichokes
  • Globe Artichokes
  • Asparagus
  • Comfrey

Run strawberries at the edge of the plots, looking to renew from runners every four years

Root Crops includes:

The Umbelliferae

  • Carrots
  • Celeriac
  • Celery
  • Fennel
  • Parsley
  • Hamburg Parsley


  • Beetroot
  • Chard
  • Spinach

From other families in the roots group:

  • Parsnips
  • Salsify
  • Scorzonera
  • Turnips

NB: Turnips are actually a brassica but are not in the ground for long so unless clubroot is a massive problem can be safely grown out of the brassica group

The benefit of this four course rotation is the gap between each crop, especially the cabbages and potatoes, occupying the same ground is extended and the other crops in the rotation have more flexibility in position.

A lot will depend on your actual requirements when you set up and use a rotation plan. The important part of your crop rotation is to keep things apart for as long as possible. Keeping a plan of your plot and marking in what has been planted where will prove of great value over the years because you are unlikely to remember what was planted where after two years.

Articles & Information on Crop Rotation

  • Crop Rotation – History & Principles of Crop Rotation
  • Crop Rotation – Plant Families or Groups for Crop Rotation
  • Crop Rotation – The Three Year Crop Rotation Plan
  • Crop Rotation – The Four Year Crop Rotation Plan
  • Crop Rotation – The Five Year Crop Rotation Plan
  • Practical Example Crop Rotation
    • Planning the Allotment Plot Crop Rotation Plan – New Plot
    • Planning the Allotment Plot Crop Rotation Plan – Previous Year
    • Planning the Allotment Crop Rotation Plan – What Potatoes to Grow
    • Planning the Allotment Plot Crop Rotation Plan – Interim Legumes
    • Planning the Allotment Crop Rotation Plan – Finished!

Crop Rotation

SERIES 29 | Episode 09

Tino Carnevale explains the reasons for rotating your crops. Crop rotation is a way of minimising pests and diseases in your garden by not planting vegetables from the same family in the same soil year after year. It looks at the nutrition needs of crops to make gardening easier and more successful. At The Patch, Tino has created a 4-bed rotation system.

Key points:
  • Split the crops into roots, fruit, leaves and legumes
  • Don’t put the same type of plant in the same soil year after year
  • Potatoes are great for breaking up new soils
  • Legumes (peas and beans) have nitrogen fixing nodules so are good at building up nutrients in the soil
  • Add lime and compost to prepare the soil for peas and plant the seeds twice as deep as the seed – up to the 2nd knuckle of your finger
  • Follow legumes with a hungry crop like kale and lettuce
  • Follow leafy crops with root and fruiting crops
  • Carrots and parsnips and good for drawing up nutrients deep in the soil
  • When beds are fallow, plant a green manure cover crop


An easy to manage crop rotation plan can be based on a four year cycle which will be sufficient to prevent the build up of problems. Your first action to create a crop rotation plan should be to create a list of the vegetables which you want to grow on your land.

This is essential because although we do not normally grow tomatoes on our plot (we grow our tomatoes in grow bags), you may want to grow lots of them. On the other hand, we like lots of onions and garlic which may not suit you. Every gardener is different as far as the crops they prefer is concerned.

We provide a useful, automated tool to generate a four year crop rotation plan for you, it’s free and can be found here.

Before you go there however, a word or two about how it works. On the first page you click the vegetables which you want to grow and then click the box to confirm your selection. This will take you to a page which does two key things. First it generates a personalised calendar for those vegetables and at the bottom of the page it will generate a four year crop rotation plan – that’s the bit you are interested in.

You will notice that the rotation plan has four plots plus another one entitled “anywhere / permanent”. You need to stick to grouping your vegetables as defined in plots 1 to 4 but the ones under the “anywhere / permanent” group can be planted in any of the four plots. This is useful because if you have a shortage of vegetables which fit into one plot, this can be evened out by including several of the “anywhere / permanent” group in the plot.

So, with the help of our crop rotation tool you will now have a very good idea of where to plant your vegetables this year, we’ll call that year 1 for convenience. In year 2 though, you need to rotate the crops so that they are grown in different plots. There are good methods and bad methods for doing that, a well accepted method to rotate your crops is shown in the picture below.

Vegetables which can be planted anywhere in the rotation plan are sweetcorn, lettuce, courgettes, cucumbers, pumpkins, squash, radish and rhubarb although it does pay to move around each year. If the above rotation plan is unbalanced because of the range of the vegetables you want to grow, French Beans and Runner Beans can also be swapped to other groups without any ill effects.

Runner Beans are included in the above crop rotation plan however our personal experience (and from the experiences of others) is that they can be grown in the same place year after year without any ill effects. Many gardeners have permanent supports for runner beans and this works fine.

To keep it all simple and clear we have named the individual vegetables in the picture above. Some books and websites refer to groups of vegetables rather than individual ones. The names used are legumes (peas, beans etc.), brassicas (cabbages, greens etc.), potatoes (includes tomatoes) and finally onions / roots.


Each year it is a good idea to test the pH of your soil in all four beds. pH is a measure of the acidity / alkalinity of your soil with a reading of 1 being the most acidic and 14 being the most alkaline. Most vegetable prefer a neutral pH which is about 6.5 to 7. Kits to test soil pH are available to buy online and also at garden centres and many diy stores.

If your soil is too alkaline (i.e. the pH level is too high) you need to add compost and manure to decrease the pH level.

If your soil is too acidic (i.e. the pH level is too low) you need to add lime (available at garden centres) to increase the pH level. When adding lime to soil read the pack instructions carefully to get the dosage correct.

Different vegetables have mild preferences for particular soil types as far as pH is concerned. However, unless you are expert at adjusting soil pH, simply aim for a level of 6.5 to 7. After several years of growing vegetables on an initially neutral soil, in all probability it will become slightly acidic and need a small dose of lime.


Since potatoes (solanum tuberosum) and tomatoes (solanum lycopersicum) are the in the same family (nightshade), it makes sense to ask if they can be grown together. I did some research to see if this is a good idea, and I found some interesting information.

So, can you grow potatoes and tomatoes together? No, you should not grow potatoes and tomatoes together. While they are both in the nightshade family, potatoes and tomatoes have different requirements for soil pH. There are also some diseases, such as early blight and late blight, which are common to both plants and can be spread between potatoes and tomatoes by insects that attack both plants.

Even though you should not plant potatoes and tomatoes together, you can still have both in your garden, provided that you take measures to prevent the spread of disease. Let’s take a look a closer look at the proper growing conditions for each plant, the common diseases for both, and how to discourage these diseases in your garden.

Reasons Not To Plant Potatoes and Tomatoes Together

There are several reasons not to plant potatoes and tomatoes together. Let’s start with one of the biggest reasons: soil pH.

Soil pH

Tomatoes prefer a slightly acidic soil pH in the range of 6.0 to 6.8, similar to most other garden plants.

Tomato plants prefer soil that is only slightly acidic, with a pH of 6.0 to 6.8.

Potatoes, however, prefer a fairly acidic soil pH of 4.8 to 5.5.

Potato plants prefer a more acidic soil, with a pH from 4.8 to 5.5.

Remember that pH is measured on a logarithmic (exponential) scale, so a pH of 5.0 is ten times as concentrated (acidic) as a pH of 6.0. Obviously, one or both plants will be unhappy if you try to grow both in the same soil.

You may be wondering why soil pH is so important for plants. Just remember that the availability of nutrients in the soil depends on the soil pH. For more information, check out this article from Research Gate, which shows the relationship between soil pH and nutrient availability.

For instance, at a pH of 4.8, calcium is starting to become less available in the soil. Potatoes might do fine in this type of soil, but tomatoes may end up with blossom end rot, a disease caused by a lack of calcium.

Blossom end rot in tomatoes is caused by a calcium deficiency.

Even worse, this can happen even if there is plenty of calcium in the soil! Remember that in this case, nutrient deficiency is caused by a pH imbalance, not by a lack of nutrients in the soil.

In short, the difference in pH preference alone is reason enough to plant potatoes and tomatoes separately.

Growth and Harvesting

Even if you managed to get potatoes and tomatoes to grow together in the same soil, you might have trouble growing them to maturity without damaging the tomatoes. Remember that potatoes have leaves above ground, but the potato tuber itself grows underground.

An early potato harvest can damage the roots of tomato plants if they are planted too close together.

Planted too close to tomatoes, the potatoes can grow large enough to impede the roots of tomato plants. You may also damage a tomato plant’s roots when harvesting nearby potatoes.

Also, remember that if potatoes and tomatoes are grown close together, there is a much higher chance that disease will be transmitted between the two plants.

Diseases Common To Potato and Tomato Plants

There are two serious diseases common to both potato and tomato plants: early blight and late blight. Let’s take a closer look at both diseases, including signs and symptoms for each plant.

Early Blight

Early blight is a common disease for tomatoes, affecting their stems, leaves, and fruit. Despite the name, early blight usually only appears on mature plants.

Symptoms include severe defoliation (loss of leaves) and scarring of fruit. The spots on fruit are black and leathery, and severely infected fruit may fall from the plant.

Early blight affects leaves, stems, and fruit on tomato plants. It also affects potatoes, and can spread between the two plants!

For potatoes, signs of early blight include small, dark brown spots on older (lower) leaves. The disease can cause fewer and smaller potatoes. The disease may also cause lesions on potato tubers themselves, with parts underneath becoming like leather or cork.

Early blight in both potatoes and tomatoes is caused by the fungus alternaria solani. A closely related fungus, alternaria tomatophila, can also cause early blight in both plants. However, alternaria tomatophila is the more common cause of the disease for tomatoes.

It is also worth noting that both fungi can also infect eggplant, which you may not want to plant close to tomatoes or potatoes in your garden. Peppers, along with eggplants, are also in the nightshade family, along with potatoes and tomatoes.

Generally, early blight develops in warm temperatures, from 59 to 80 degrees Fahrenheit. High humidity levels (90% or greater) also encourage growth of early blight, since it is a fungus.

Remember that both alternaria solani and alternaria tomatophila can survive the winter in soil, compost, or other organic matter. This means that soil may need to be left unplanted for many years to eliminate the disease.

Even worse, early blight can reside in infected potatoes, so if you buy potatoes that are infected and try to plant them after they sprout, you can end up introducing early blight to your garden.

It is also worth noting that you should not compost infected plants. Instead, burn them or dispose of them immediately. Since the spores can be spread by wind, rain, irrigation, machinery, or human contact, it is important to identify infected plants early and remove them quickly to prevent the spread of early blight in your garden.

To prevent early blight in the first place, choose disease-resistant varieties of potatoes and tomatoes in the future.

According to the University of Minnesota, some tomato varieties that are resistant to early blight include Iron Lady, Mountain Supreme, and Mountain Magic.

Also, avoid irrigation in cool, cloudy weather, and water early to allow plants to dry before nightfall. The longer the leaves stay wet, the better the chance of fungus growth, and thus the more opportunity early blight has to take hold.

For more information, check out this article from the University of Minnesota on early blight in tomatoes and this article from Michigan State University on early blight in potatoes.

Late Blight

Late blight can affect leaves, stems, and fruits of tomato plants. It can spread very quickly and can be devastating to gardens. The disease was responsible for the Irish potato famine of 1840.

The oomycete (fungus-like organism) Phytophthora infestans is the cause of late blight. The symptoms include large, brown spots on leaves and stems. Fruits may also develop firm, brown spots.

Late blight causes dark brown spots outside and inside potatoes.

Eventually, other bacteria can invade the weakened fruit and cause mushiness. When humidity is high, powdery white fungus appears on infected plants. With severe late blight infections, a foul odor may be detected.

Late blight will spread most at temperatures between 60 and 70 degrees Fahrenheit, during periods of high humidity.

The disease can survive over the winter, but is not as likely to do so as early blight. In light of this, do not compost any infected plants. Instead, burn them or dispose of them immediately.

Late blight can produce thousands of spores in less than a week, potentially infecting your entire garden’s potato and tomato crop, along with those of neighboring gardens.

The best way to avoid late blight is to cultivate disease-resistant varieties of potatoes and tomatoes. According to the University of Minnesota, tomato varieties that are resistant to late blight include Mountain Magic, Plum Regal, and Iron Lady.

You should also inspect established tomato plants that you purchase, in order to ensure that they are not infected with late blight. Also, be sure to water at the bottom of plants – avoid getting the leaves wet, and avoid watering late in the day so that the plant does not stay wet overnight.

For more information, check out this article from the University of Minnesota on late blight and this article from the University of Maryland on late blight.

How To Use Crop Rotation to Prevent Disease In Your Garden

The best way to discourage early blight, late blight, and other diseases in your garden is to employ crop rotation. Crop rotation simply means that you do not plant the same crop in the same location two years in a row.

Sometimes, crop rotation calls for 3 or even 4 year rotation cycles. For instance, you might plant leaves (lettuce), fruits (tomatoes), roots (carrots), and legumes (peas) in each of the four years in your crop rotation cycle.

Including peas in your crop rotation can help to prevent disease – they also help to add nitrogen to the soil.

Even though potatoes (roots) and tomatoes (fruits) are in different categories, they should not be planted in the same area in successive years. If you want to grow all 4 common nightshade plants (potatoes, tomatoes, peppers, and eggplant) in your garden, here is a crop rotation method you can use.

Peppers are another good plant to add to your crop rotation. Like potatoes and tomatoes, they are in the nightshade family.

First, split your garden into 16 equal sections: 4 rows by 4 columns. Assign one plant to each row, depending on growing requirements such as sunlight and pH (remember our discussion of soil pH earlier!) Be sure to keep the tomatoes and potatoes far apart to prevent the spread of disease between the two. For instance:

Row 1 – tomatoes

Row 2 – peppers

Row 3 – eggplant

Row 4 – potatoes

Then, assign a different column to each plant. For instance:

Column 1 – tomatoes

Column 2 – potatoes

Column 3 – eggplant

Column 4 – potatoes

Plant each crop in the correct section, based on its row and column. Every year after that, you should move each plant one column to the right. (If a plant is already at the far right, move it to the far left).

This prevents the spread of early and late blight between potatoes and tomatoes, and ensures that there are four years between plantings of these crops in the same area.


By now, you should have a better understanding of why it is a bad idea to plant potatoes and tomatoes too close together. Not only do they require different soil pH levels, but they also share diseases that can spread between the plants easily.

I hope you found this article helpful – if so, please share it with someone who will find the information helpful. If you have any questions or advice of your own on potatoes, tomatoes, and crop rotation, please leave a comment below.

Rotating vegetable crops is an easy juggle in large vegetable gardens. Rearranging small gardens can be more challenging, but even minimal rotation will make a big difference. In a raised bed, if you use a planting mix that is changed out every two or three years, crop rotation is less important. (If you grow plants in containers, simply change out the potting mix every year and you won’t have to worry about crop rotation at all. For best results, choose a premium potting mix such as Miracle-Gro® Potting Mix.)

Start by making a rough sketch of the garden as you plant and date the sketch in your garden journal. Nothing fancy, “X marks the spot” will do. Note each planting of the year if you make successive plantings in spring, summer, and fall. Sketches in your garden journal remind you how you planted the garden last year so you won’t follow the exact same plan this year.

Putting your garden rotation on paper also lets you plan ahead to know how many plants of each type you need. If you note the variety name, such as “Bonnie Original Tomato,” instead of just “Tomato,” you’ll have a record in case you can’t remember the name of your favorite tomato.

If you’re not sure whether a spot gets enough light, try this test. On a sunny to partly sunny day, turn off all lights and periodically check on the natural sunlight. How much sun does the spot get throughout the day?

‘TomTato’ tomato and potato plant unveiled in UK

Image caption The TomTato has been described as a “veg plot in a pot”

A plant that produces both tomatoes and potatoes, called the TomTato, has been developed for the UK market.

Ipswich-based horticultural firm Thompson and Morgan said the plants were not genetically modified.

Similar plants have been created in the UK, but the firm said it was thought to be the first time they had been produced on a commercial scale.

Guy Barter, of the Royal Horticultural Society (RHS), said it was looking at the plant with “real interest”.

Mr Barter said many of these plants – created by a technique known as grafting – had been created before but taste had previously been a problem.

“We’re looking at it with real interest because Thompson and Morgan are a really reputable firm with a lot to lose, but I wouldn’t rule out that it could be a very valuable plant to them,” said Mr Barter, who is a contributor to BBC Gardener’s World.

“In the past we’ve never had any faith in the plants – they’ve not been very good – but grafting has come on leaps and bounds in recent years.

“Many people don’t have that much space in their gardens and I imagine this sort of product would appeal to them.”

Thompson and Morgan director Paul Hansord claimed the tomatoes were tastier than most shop-bought tomatoes and said the plant had taken a decade of work.

“It has been very difficult to achieve because the tomato stem and the potato stem have to be the same thickness for the graft to work,” he said.

“It is a very highly skilled operation. We have seen similar products. However, on closer inspection the potato is planted in a pot with a tomato planted in the same pot – our plant is one plant and produces no potato foliage.”

The firm said the plants last for one season and by the time the tomatoes are ready for picking, the potatoes can be dug up.

It added both ends of the plant had been tested for alpha-solanine – a poison that can be produced in both crops depending on growing and storage conditions – and it had been certified as safe.

A similar product, dubbed the “Potato Tom”, was launched in garden centres in New Zealand this week.

This article will show you how to grow tomatoes and potatoes on one plant by grafting a tomato plant onto a potato plant. As summer slowly rolls to an end, we often find ourselves with an abundance of tomatos. Many of the fruit remains green and not fully ripened. I typically find myself asking, “What can I do different next year to get more fruit for my effort?”

It turns out there is an answer: grafting tomato plants to potatoes.

Grafted Plant Diagram (click image to see image source)

Over the centuries, smart gardeners and farmers have developed successful methods to use potato root stock to support tomatoes that may not otherwise be well suited to poor soil conditions in your garden.

This is a great way to save space in your garden! You can start your potatoes early in the growing season to let them mature. Leave some of the potato plants in place and perform the following grafting process to give your tomato plants a head start!

The process:

  1. Taking the potato plant (called the “stock”) cut the stem about 1-inch above the ground and split the stem in a V-shape.
  2. At the tomato plant (called a “scion”), cut the stem with at least 6 to 8 inches of length with a straight across cut. I recommend choosing a tomato plant that has a stem roughly the same diameter as the potato plant rootstock.
  3. Shape the cut end of the tomato plant to a wedge shape so that it will fit into the potato plant stem’s V-shape cut.
  4. Carefully slide the tomato plant stem onto the potato rootstock.
  5. Wrap the graft location with grafting tape in order to hold the two plants together.
  6. The grafting tape needs to remain in place until the tomato plant begins to show new growth.

Here is an illustration of the grafting steps described above:

Grafting Scion Section to Stock (click image to see image source)

Why does this grafting process work? Tomato plants and potato plants are part of the family of plants called “nightshades”. Both plants contain alkaloids that help protect the plants from insects (they can even be used to make an organic liquid pest control solution for aphids: Organic Aphid Control)

A point of caution, grafting can potentially affect the flavor of the tomato fruit. Also, grafted plants may yield less fruit than two separate plants grown from seeds. On the other hand, a major benefit is the grafting process will save you a lot of time and space!

Tomato-Potato Graft Plant Starts (click image to see image source)

If you end up trying this next year, or plant to grow potatoes in general, we have the perfect garden box for potatoes (and for lots of other things too). We call it TogetherFarm Blocks. This is a modular garden box system made from 100% recycled, food-grade plastic that can be put together in any shape or size. Because it is modular, it is perfect for growing potatoes and tomatoes. Tomatoes will send out roots at any point that the stem is below the surface of the soil. So, as the plant grows, you can add additional layers onto your modular garden box to give the plant even more strength and fruitfulness. With the potatoes, TogetherFarm Blocks makes it simple at harvest time. Simply pull apart the blocks to be able to get to all the potatoes underground. So cool! We are currently in the last few days of a Kickstarter Campaign to get these blocks to market. If you pledge now, we will ship you a kit at the end of January of next year – just in time for next year’s growing season. Here is a link to TogetherFarm Blocks on Kickstarter as well as a picture of an assembled box. Help us reach our goal and get incredible rewards. Pledge now!


TogetherFarm Blocks – an eco-friendly and easy way to build a garden box

Happy Gardening,

Matt and the TogetherFarm Produce Evangelists

45,956 total views, 22 views today


Tomatoes and potatoes growing from the same plant! Great fun and it really works, we should know we have been growing and enjoying them since approximately 1975!

The spelling of this interesting plant can be done in so many different ways such as tomtato, tom tato, we simply like tomtatoes as they produce lots of delicious tomato fruits and potatoes!

Recommended for outdoor planting only.

Specially featured many years ago in the book Indoor Farming by David Wickers and by Anglia TV.

  • Soil Preparation.
  • Only plant out from late May until mid June for a superb crop of potatoes and the best flavoured tomatoes you’ve ever tasted.
  • The Tomtatoe requires a soil that is rich in humus or compost, spent mushroom compost is ideal! Work this in to the soil, pricked in with a fork, to the top 4 – 6″ (10 – 15 cm), the idea being that the soil is open and `fluffed up’. You can incorporate an organic plant feed at about 4 ozs (110 grammes) per square yard (0.85 square metres), again just lightly pricked into the soil.
  • Planting You Tomtatoes – Plant Pot And All!
  • Ideally you should plant 3 feet (90 cm) apart by 2 feet (60 cm)
  • Do not remove the pot. You should plant the complete pot as it is and the rim or top of the pot should be 4″ (10 cm) from the surface of the soil. The bottom of the pot should be in direct contact with moist compost or even peat, it must not dry out. At planting time place a 4 foot (120 cm) cane against the outside of the pot pushed into the soil; in time you will need to tie in loosely the Tomato part of the plant. No harm will come to the Tomato part of the plant being buried by 4″ (10 cm) as roots will grow from the stem.
  • Growing.
  • The potato shoots/leaves have a spoon shaped appearance and as they grow draw them aside to encourage them to spread outwards and away from the central plant.
  • When the shoots are about 9″ (22 cm) long cover the lower 6″ (15 cm) with soil or compost – this is where your potatoes grow from.
  • The Tomato part of the plant will grow upwards in the usual way, pinch out the Tomato shoots one leaf beyond the fourth flower truss.
  • When the first flower trusses appear of the tomato, feed at 10 day intervals by way of a good drench of No2 Strength of our Instant Life solution; this should be watered over all the foliage and of the potato part of the plant too.
  • Important – Do not do this in bright sunlight, it should be done late evening only, after the sun has gone down so that combined with the beneficial effects of night dew as well as `feed’ getting to the roots it is also absorbed through the foliage, ie foliar feeding.
  • The better the soil and the loose compost the better your ultimate crop of both potatoes and tomatoes.
  • Do not be in a hurry to harvest these special potatoes which are well suited for boiling, saute, chips or as `new potatoes’; boil and allow to go cold, chop with a little chive or onion and serve just warmed with a little fresh mint in a steamer – delicious!
  • When the potato haulm or leaves turn yellow brown in late Summer the plant is `spent’ meaning it will not produce any more potatoes.
  • Be sure to harvest before frost.
  • New Potatoes In March?
  • The Victorians new a trick or two about gardening – so do we! Try this experiment.
  • In late Summer remove some potatoes the size of small eggs. Before the skins have set, ie dried in the sun, have an old biscuit tin (not a polythene bag) in which you have placed some moist, not soggy wet, sharp sand. Lay your potatoes not touching on the sand and cover with sand – about 2″ (5 cm), on top place another layer and finally pack with sand. Replace the lid and bury the tin in a frost free place in the soil. Come Christmas, January – March as you please remove the tin and remove the potatoes. Do not peel but steam ’til cooked. Serve with a knob of butter and a little mint that you froze for Winter use and, yummy, you have new potatoes out of Season!
  • Top Tips
  • Always keep your Tomtatoes free of weeds by either hand pulling or a light hoe.
  • Do not use herbicides/weed killers.
  • At the end of Season lift the old pot and discard.
  • Always grow Tomtatoes on a fresh patch each year!
  • Growing in Grow Bags? Yes you can but ideally you would need two grow bags, one laid on top of another! You would plant through the top bag into the lower bag. The potatoes would be produced in the top bag. Cropping potential would not be so high by this method as growing in the open soil.

Nightshades have a reputation as bad actors in a variety of chronic conditions, such as arthritis, fibromyalgia, and IBS. But what do we really know about how these foods affect our health?

To skip to a specific section, choose a heading below:

Meet the Nightshade (Solanaceae) Family:

  • Tomatoes
  • Tomatillos
  • Eggplant
  • Potatoes
  • Goji Berries
  • Tobacco
  • Peppers (bell peppers, chili peppers, paprika, tamales, tomatillos, pimentos, cayenne, etc)

At first glance, the nightshades may look like a random collection of foods that couldn’t possibly be related. However, every nightshade plant produces fruits that all sport that same adorable little green elfish hat. Of the foods above, only tomatoes, eggplants, goji berries and peppers are “fruits” (the potato is a tuber and tobacco is a leaf). The fruits of potato and tobacco plants wear the same telltale hat, but we don’t eat the fruits of those plants.

What are glycoalkaloids?

Glycoalkaloids are natural pesticides produced by nightshade plants. Glycoalkaloids are bitter compounds which are found throughout the plant, but their concentrations are especially high in leaves, flowers, and unripe fruits. They are there to defend plants against bacteria, fungi, viruses, and insects.

Cherries, apples, and sugar beets also contain small amounts of glycoalkaloid even though they are not nightshades.

How do glycoalkaloids kill pests?

  • Glycoalkaloids act as invisible hand grenades. They bind strongly to the cholesterol in the cell membranes of predators, and in so doing, they disrupt the structure of those membranes, causing cells to leak or burst open upon contact.
  • Glycoalkaloids are neurotoxins. They block the enzyme cholinesterase. This enzyme is responsible for breaking down acetylcholine, a vital neurotransmitter that carries signals between nerve cells and muscle cells. When this important enzyme is blocked, acetylcholine can accumulate and electrically overstimulate the predator’s muscle cells. This can lead to paralysis, convulsions, respiratory arrest, and death. Military “nerve gases” work exactly the same way.

Ok, so glycoalkaloids are clearly nightmarish compounds for the cells of tiny creatures daring to munch upon nightshade plants, but what do we know about their effects on human health?

Nightshade glycoalkaloid health “benefits“

Health benefits? From a pesticide? Hmmm…

Since most people believe plant compounds are good for humans, when scientists conduct experiments with plant extracts, they are more likely to look for health benefits than health risks.

  • Glycoalkaloids are anti-inflammatory. Glycoalkaloids have been shown to reduce inflammation in laboratory animals. This is likely due to the fact that glycoalkaloids are structurally similar to compounds called glucocorticoids, which have well-known anti-inflammatory properties. Familiar examples of glucocorticoids include cortisol (our body’s natural stress hormone), and Prednisone, a commonly-prescribed anti-inflammatory medicine. It should be noted, however, that just because glycoalkaloids or glucocorticoids can reduce inflammation doesn’t mean they are always good for you. Prednisone is not something most of us should be taking every day, because it has numerous damaging side effects, and elevated levels of natural cortisol in our bodies weaken our immune system and slow our metabolism.
  • Glycoalkaloids kill bacteria and viruses. It should also not be surprising that glycoalkaloids have been shown in laboratory studies to possess antibiotic and antiviral properties, since this is what nature designed them for.
  • Glycoalkaloids have anti-cancer properties. In laboratory (in vitro) studies, glycoalkaloids can trigger cancer cells to self-destruct. This process is called “apoptosis.” Unfortunately, they can also cause healthy non-cancerous cells to do the same thing. Cancer studies in live animals and humans (in vivo) have not yet been conducted. The problem with so many anti-cancer plant compounds is that they are double-edged swords, killing both cancer cells and healthy cells alike:

“…the undifferentiating destruction of both cancer and noncancerous cell lines…leads to questions of therapeutic uses of glycoalkaloids due to safety considerations. However, it is difficult to translate the results of an in vivo trial in vitro. Therefore, both animal and human experiments are essential to confirm or disprove the in vivo data observed in these studies.” .

Health Risks of Nightshade Glycoalkaloids

  • Glycoalkaloids destroy cell membranes. Research has shown that glycoalkaloids can burst open the membranes of red blood cells and mitochondria (our cells’ energy generators).

    “Some scientists have wondered whether glycoalkaloids could be one potential cause for “leaky gut” syndromes due to their ability to poke holes in cells: “…glycoalkaloids, normally available while eating potatoes, embed themselves and disrupt epithelial barrier integrity in a dose-dependent fashion in both cell culture models and in sheets of mammalian intestine…animals with the genetic predisposition to develop IBD, demonstrated a greater degree of small intestinal epithelial barrier disruption and inflammation when their epithelium was exposed to the potato glycoalkaloids chaconine and solanine.”

  • Glycoalkaloids cause birth defects in laboratory animals.

Nightshades and Mental Health

Centuries ago, the common eggplant was referred to as “mad apple” due to belief that eating it regularly would cause mental illness.

Due to widespread pro-plant food bias, the vast majority of scientific studies of nightshades explore their potential benefits rather than their downsides, so we do not have the studies we wish to have about how these interesting foods affect our well-being.

However, there have been plenty of documented cases of nightshade toxicity that demonstrate to us how poisonous they can be to our central nervous system, capable of causing severe neuropsychiatric side effects in human beings:

“In cases of mild glycoalkaloid poisoning symptoms include headache, vomiting, and diarrhea. Neurological symptoms were also reported, including apathy, restlessness, drowsiness, mental confusion, rambling, incoherence, stupor, hallucinations, dizziness, trembling, and visual disturbances.”

In a group of children who suffered from solanine poisoning as a result of eating potatoes that had been in storage for too long, severe psychiatric side effects were observed:

“The largest series of solanine poisoning involved an English day school where 78 schoolboys developed diarrhea and vomiting after eating potatoes stored since the summer term. Symptoms began 7-19 hours after ingestion with vomiting, diarrhea, anorexia, and malaise. Of the 78 boys, 17 were admitted to the hospital. Other symptoms included fever (88%), altered mental status (drowsiness, confusion, delirium) (82%), restlessness (47%), headache (29%), and hallucinations (23%). Three boys were seriously ill with hypotension, tachycardia, and stupor out of proportion to fluid and electrolyte imbalance. These boys were discharged 6-11 days after admission, and they had nonspecific symptoms and visual blurring for several weeks after release from the hospital.”

Keep in mind that these reactions just happened to be recorded due to their severity. We have no documented information about how everyday consumption of nightshades affects sensitive individuals, only numerous on-line personal accounts of mental health problems such as anxiety, panic, and insomnia that were alleviated by removal of nightshades from the diet. I personally experience profound insomnia and mild panic symptoms when I eat nightshades, which makes sense because glycoalkaloids overstimulate the nervous system.

If you experience anxiety or insomnia and are curious to know more about nightshades and the other foods most likely to be contributing to your symptoms, I recommend you read my Psychology Today article “5 Foods Proven to Cause Anxiety and Insomnia.”

Fruits vs vegetables: here we go again!

Those of you who are familiar with my philosophy about plant foods know that I believe vegetables are far less trustworthy when it comes to our health than edible fruits, and nightshades make this point nicely.

As you will see below, even though nightshade fruits contain glycoalkaloids, they either contain lower amounts of these potentially toxic compounds or contain gentler versions of them.

Luckily, most of the edible nightshades–eggplant, tomatoes, goji and peppers– are fruits (fruits by definition contain seeds). Tobacco is a nightshade vegetable, but it is typically smoked, not eaten, so the only nightshade vegetable humans consume is the beloved potato.

Potato Glycoalkaloids

All potatoes are nightshades except for sweet potatoes and yams.

Potato plants make two glycoalkaloids: alpha-chaconine and alpha-solanine. These are the most toxic glycoalkaloids found in the edible nightshade family. Alpha-chaconine is actually more potent than alpha-solanine, but solanine has been studied much more thoroughly, and is therefore more familiar.

There are numerous cases of livestock deaths from eating raw potatoes, potato berries, and potato leaves, but people don’t eat these things. However, there are well-documented reports of people getting glycoalkaloid poisoning from potatoes, typically from eating improperly stored, green, or sprouting potatoes. At low doses, humans can experience gastrointestinal symptoms, such as vomiting and diarrhea. At higher doses, much more serious symptoms can occur, including fever, low blood pressure, confusion, and other neurological problems. At very high doses, glycoalkaloids are fatal.

Another reason why many people may not be bothered by potatoes is that glycoalkaloids are very poorly absorbed by the gastrointestinal tract, so, if you have a healthy digestive tract, most of the glycoalkaloid won’t make it into your bloodstream. However, if you eat potatoes every day, levels can build up over time and accumulate in the body’s tissues and organs, because it takes many days for them to be cleared. Also, since glycoalkaloids have the ability to burst cells open, they can theoretically cause damage to the cells that line your digestive system as they are passing through (this has been proven in animal studies but there are no human studies, to my knowledge).

Due to known toxicity, the FDA limits the glycoalkaloid content in potatoes to a maximum of 200 mg/kg potatoes (91 mg per pound). Human studies show that doses as low as 1 mg glycoalkaloid per kg body weight can be toxic, and that doses as low as 3 mg/kg can be fatal. This means that, if you weigh 150 lbs, then doses as low as 68 mg could be toxic, and doses as low as 202 mg could be fatal.

Glycoalkaloid levels of a few prepared potato products are available :

  • Potato chips, 1 oz bag: 0.36 to 0.88 mg chaconine and 0.29 to 1.4 mg solanine. Total glycoalkaloid concentrations range from 2.7 to 12.4 mg per bag.
  • Fried potato skins, 4 oz: 4.4 to 13.6 mg chaconine and 2.0 to 9.5 mg solanine. Total glycoalkaloid concentrations range from 6.4 to 23.1 mg per 4 oz serving.

Potato Processing 101

The vast majority of glycoalkaloid is in the potato skin, so peeling will remove virtually all of it. Glycoalkaloid levels can be dangerously high in unripe and sprouting potatoes; any greenish areas or “eyes” should be removed or avoided.

Glycoalkaloids survive most types of cooking and processing. In fact, deep frying will increase levels if the oil isn’t changed frequently, so fried products such as potato skins and french fries can contain relatively high amounts:

“Mechanical damage to potato tissue increases the concentration of glycoalkaloids available for consumption. In addition, frying potatoes at high temperatures does not inactivate but instead serves to preserve and concentrate glycoalkaloids within the potato, leaving them available for ingestion and delivery to the intestine…”

  • Boiling—reduces glycoalkaloids by a few percentage points
  • Microwaving—reduces glycoalkaloids by 15%
  • Deep frying at 150C (300F)—no effect (McDonald’s uses 340F degree oil)
  • Deep frying at 210C (410F)—reduces glycoalkaloid content by 40%

Tomato Glycoalkaloids

Tomato nightshades include all types of tomatoes: cherry tomatoes, green tomatoes, yellow tomatoes and ripe red tomatoes.

Tomatoes produce two glycoalkaloids: alpha-tomatine and dehydrotomatine. The majority is in the form of alpha-tomatine, so we’ll focus on that one here.

As tomatoes ripen, alpha-tomatine levels drop dramatically, from about 500 mg/kg in green tomatoes to about 5 mg/kg in ripe red tomatoes, or 2.3 mg/lb. Artificially ripened fruits may contain higher amounts than sun-ripened fruits.

Tomato glycoalkaloids are about 20 times less toxic than potato glycoalkaloids. (Fruits: 2, Veggies: 0). There are no dosage studies of tomatine in humans, but studies in mice tell us that 500 mg tomatine per 1 kg body weight (or 227 mg per pound) is the median lethal dose (“LD50”). This doesn’t tell us how much it would take to kill a 150 lb person; it only tells us that it would take 34 grams of tomatine to kill a 150-pound mouse. Since ripe tomatoes contain 5 mg/kg or 2.3 mg/lb of tomatine, it would take nearly 15,000 pounds of tomatoes to kill this Mighty Mouse (probably many fewer pounds if you were to simply hurl them in his general direction from across the room). Since green tomatoes contain 100 times more tomatine, it would only take 150 pounds of green tomatoes to kill the overgrown rodent. We do not understand the effect of low doses of tomatine over time on any type of animal, including humans.

Eggplant Glycoalkaloids

Centuries ago, the common eggplant was referred to as “mad apple” due to belief that eating it regularly would cause mental illness. Eggplants produce two glycoalkaloids: alpha-solamargine and alpha-solasonine. Solamargine is more potent than solasonine.

Whereas potato glycoalkaloids are located mainly in the skin, in eggplants, glycoalkaloids are found primarily within the seeds and flesh; the peel contains negligible amounts.

The common eggplant (solanum melongena) contains 10-20 mg of glycoalkaloid per kg (or 4.5 to 9 mg per pound of eggplant). Eggplant glycoalkaloids are considered relatively nontoxic compared to potato glycoalkaloids (Fruits: 3, Veggies: 0).

The median lethal dose (LD50) in rodents is 1.75 mg/kg. This means that it would take at least 13 pounds of eggplant to kill a 150 lb monster mouse. .


Red and green bell peppers contain less than 10 mg of glycoalkaloid per kg. This is a very small amount, so if you react badly to peppers, you are either very sensitive, or you are responding to other compounds within the peppers, such as the notoriously hot and spicy capsaicinoids.

What about Goji Berries?

Your guess is as good as mine…I could not locate any scientific information about glycoalkaloids in these foods.

Nightshades and Nicotine

Nightshade foods also contain small amounts of nicotine, especially when unripe. Nicotine is much higher in tobacco leaves, of course. Scientists think that nicotine is a natural plant pesticide, although it is unclear exactly how it works to protect plants from invaders. The amount of nicotine in ripe nightshade foods ranges from 2 to 7 micrograms per kg of food. Nicotine is heat-stable, therefore, it is found in prepared foods such as ketchup and French fries. The health effects of these small doses is not known, but some scientists wonder whether the nicotine content of these foods is why some people describe feeling addicted to them. In my opinion, it is more likely that the high carbohydrate content of those foods is responsible for their addictive properties.

Do you have nightshade sensitivity?

As with any food sensitivity, the only way to find out is to remove nightshades from your diet for a couple of weeks or so to see if you feel better. There are ZERO scientific articles about nightshade sensitivity, chronic pain, or arthritis in the literature, however, the internet is full of anecdotal reports of people who have found that nightshades aggravate arthritis, fibromyalgia, or other chronic pain syndromes. I am personally very sensitive to nightshades; they cause me a variety of symptoms, most notably heartburn, difficulty concentrating, pounding heart, muscle/nerve/joint pain, and profound insomnia. Everyone is different, so as always, you’ll need to discover for yourself whether these foods may pose problems for your individual chemistry. However, given what we know about nightshade chemicals, common sense tells us that these foods are well worth exploring as potential culprits in pain syndromes, gastrointestinal syndromes, and neurologic/psychiatric symptoms.

Recommended Nightshade-Free Cookbooks

Since nightshades in various forms find their way into so many familiar dishes, it can be daunting to know where to begin when first trying to cook without them. While there are many nightshade-free cookbooks on the market, these two stand head and shoulders above the rest because they both focus on whole foods recipes free of other common food culprits.

The Healing Kitchen: 175+ Quick & Easy Paleo Recipes to Help You Thrive is co-authored by the fabulous Sarah Ballantyne (aka PaleoMom) who has an impressive PhD in medical biophysics. This cookbook eliminates nightshades, grains, legumes, nuts, seeds, eggs, and dairy. In addition to delicious recipes, the authors do a beautiful job of explaining the science behind healthy eating, encouraging you to stay positive by focusing on what you CAN eat.

The Autoimmune Paleo Cookbook: An Allergen-Free Approach to Managing Chronic Illness is written by nutritional therapist/cook Mickey Trescott. This beautiful and supportive cookbook includes helpful meal and shopping plans. All recipes are free of nightshades, grains, legumes, nuts, seeds, eggs, and dairy. Quite a few recipes rely on coconut and garlic, so if you have sensitivities to these foods, it may not be the one for you, but otherwise it’s a wonderful choice.

Other Food Sensitivity Syndromes

If nightshades aren’t your problem, you may be interested to know that there are many other foods which can cause real health issues for people.

  • To read about foods that interfere with proper thyroid function, see my post: Foods That Cause Hypothyroidism
  • To learn how aged, cured, fermented, smoked and processed foods can cause or worsen allergies, migraines, PMS/peri-menopausal symptoms, IBS, anxiety, or insomnia, read Freshness Counts: Histamine Intolerance
  • To learn which foods are most likely to cause acne, check out my post The Complexion Connection
  • To understand the risks of eating broccoli, kale, and other cruciferous vegetables, see my post Is Broccoli Good For You?
  • To learn which foods are most likely to cause IBS check out Common Constipation Culprits and Is Fructose Malabsorption Causing your IBS?

Tagged with: Arthritis • Cancer • Eggplant • Fibromyalgia • Glycoalkaloid • Goji berries • IBS • Nicotine • Nightshades • Peppers • Potatoes • Tomatoes

Barceloux DG 2009. Potatoes, tomatoes, and solanine toxicity. Dis Mon 55(6):391-402.

Friedman M. Tomato glycoalkaloids: role in the plant and in the diet. J Agric Food Chem2002; 50:5751-5780. UDSA, Albany California.

Hansen AA. Two fatal cases of potato poisoning. Science 1925; 61(1578): 340-341.

Jones PG and Fenwick GR 1981. The glycoalkaloid content of some edible solanaceous fruits and potato products. Journal of the Science of Food and Agriculture 32(4):419-421.

Korpan YI et al. Potato glycoalkaloids: true safety or false sense of security? Trends in Biotechnology 2004; 22(3): 147-151.

McMillan M and Thompson JC. An outbreak of suspected solanine poisoning in schoolboys: examinations of criteria of solanine poisoning. Q J Med 1979; 48(190): 227-243.

Mensinga TT et al. Potato glycoalkaloids and adverse effects in humans: an ascending dose study. Regulatory Toxicology and Pharmacology 2005;41: 66-72. University of Utrecht, The Netherlands.

Milner SE et al. Bioactivities of glycoalkaloids and their aglycones from Solanum species. J Agric Food Chem 2011; 59: 3454–3484. University College, Cork Ireland.

Patel B et al. Potato glycoalkaloids adversely affect intestinal permeability and aggravate inflammatory bowel disease. Inflammatory Bowel Diseases 2002; 8 (5): 340-346.

Sanchez-Mata MC et al. r-Solasonine and r-Solamargine Contents of Gboma (Solanum macrocarpon L.) and Scarlet (Solanum aethiopicum L.) Eggplants J Agric Food Chem 2010; 58: 5502–5508.

Siegmund B et al. Determination of the nicotine content of various edible nightshades (Solanaceae) and their products and estimation of the associated dietary nicotine intake. J Agric Food Chem 1999;47: 3113−3120.

Please note that after 30 days, Dr. Ede may not personally respond to comments, however comments shall remain open to encourage community discussion. 8.53K Shares 8.53K Shares Tagged with: Arthritis • Cancer • Eggplant • Fibromyalgia • Glycoalkaloid • Goji berries • IBS • Nicotine • Nightshades • Peppers • Potatoes • Tomatoes

Explaining Vegetable Families: Tomatoes, Eggplants, Potatoes and Peppers Are All Nightshades

Tomatoes, peppers, potatoes, and eggplants form the backbone of many backyard gardens. These seemingly diverse crops are all members of a single plant family, the nightshades (Solanaceae). Study the flowers and fruits of nightshades, and you’ll find identical structures. This relationship is a clue that these crops benefit from somewhat similar cultural conditions, and succumb to many of the same pests and diseases.

Here’s a plateful from “week 11” at Clagett Farm CSA. Four of the eight items are from the nightshade family.

The nightshades are among the easiest vegetables to put in the ground. Tomatoes, peppers, and eggplants are always found in late spring as little starter plants at nurseries. What gardener can resist those baby plants, when visions of vine ripe, homegrown vegetables dance in his or her head? These three are simple to grow from seed as well. Tomato, pepper, and eggplant seeds germinate faithfully and grow quickly. Their cousin, the potato, is not grown from seed, but planted in spring as purchased, cut up,”seed potatos”. All of these crops need full sun and grow best on a rich, nearly neutral soil. They should be watered regularly during the season to keep them growing vigorously. Add mulch once the soil is warm and the weather is balmy.

Hot or cold?

A temperature preference separates the potato from its three cousins here. Potatoes need a cooler soil, hence their association with Idaho and Maine, and not, say, Florida and Texas. On the other hand, tomatoes, peppers and eggplants must only be planted when the soil is warm, and enjoy hot weather for the most part. Seeds sprout more quickly when warm, and a raised garden bed provides warmer soil. Eggplants are the most heatloving of this bunch. Peppers and tomatoes can suffer when temps top 90 degrees F.

Despite starting as tiny seeds, or pieces of tuber, these plants are fast growing and need roomy accomodations. Potatoes must be hilled; that is, dirt or straw is mounded around the stems as they grow. The tubers will form in the mound. Tomatoes of all kinds do best with cages or support, and make it a tall sturdy support for “indeterminate” types. Peppers and eggplants become a small bush, so space them about two feet apart as you would for tomatoes.

For many gardeners these plants go gangbusters, and for many they simply go bust. These can be some of the more disease prone, finicky crops in the garden. They are all subject to various wilts, rots, and blights. You might improve your odds with tomatoes by only planting disease resistant hybrids. They have the capital V, F, N, and T, or some combination thereof, after their name. More importantly, change the location of your nightshade vegetables every year. Give the plants good general care. Water only at the soil surface, keeping the leaves dry.

Bugs can bug the nightshades quite a bit. There are the “trademark” pests (Colorado potato beetle, tomato hornworm) and plenty of general garden pests (flea beetles, aphids and others) which find most nightshades as delectable as we do. Peppers being, well, peppery, are fairly free from insects. Check tomatoes, peppers, and eggplants often. Handpick big bugs, and try natural soaps on the those smaller and more numerous.

More fun with nightshades

Goji, or wolfberry, is a nightshade. And that’s all I have to say about goji, because Diana Wind, RD describes goji in an interesting article, “Superfruit – Goji Berry, Lycium babarum.”

The nightshade (Solanaceae) family of plants contains some of the most useful crops in the world, the loveliest flowers, and also some of the most deadly plants. It’s really no surprise that tomatoes were once thought to be toxic. This same family includes deadly nightshade (Atropa belladonna), devil’s trumpet (Datura) and tobacco (Nicotiana.) The neurotoxins in the poisonous Solanaceae are refined into medically useful compounds such as stimulants, sedatives, antinausea drugs, and opthalmic drops for pupil dilation. Mankind has undoubtedly both greatly benefitted, and suffered, from wide cultivation of various nightshades.

Solanine is a nightshade toxin, associated with green skin on potato tubers. According to Harriet A. Hall, MD, writing at Science Based Medicine, it’s virtually impossible to eat enough solanine from potatoes to cause illness. Solanine is bitter, so for palatability, always peel green skin and remove eyes from potatoes before eating them. Also don’t eat any tiny fruits that may form on potato plants.
Datura and Brugmansia may be the most beautiful of the non-food nightshades. These tropical flowering bushes produce gorgeous, intensely fragrant, trumpet shaped flowers. Having grown both Datura and Brugmansia, I urge other gardeners to give them a try. Their special needs are worth the extra care, at least once.

Tomatillos, cape gooseberries, and edible ground cherries are all found in the Physalis genus of nightshades.

~ ~ ~ ~ ~

Photo courtesy of Steven Walling, in Wikimedia, licensed under the Creative Commons Attribution 2.0 Generic license

Why nightshade vegetables get a bad rap

Take the nightshade vegetables or Solanaceae, a plant family that includes eggplant, peppers, potatoes and tomatoes. (The term ‘nightshade’ may have been coined because some of these plants prefer to grow in shady areas, and some flower at night.) An online search of “nightshade vegetables” yields results linking them to a host of health ailments from arthritis to migraines. Naturo­paths sometimes recommend that people with arthritis avoid nightshades. And Patricia J. Wales, a naturopathic doctor in Calgary, says naturopaths may suggest that people with osteoarthritis eliminate nightshades. These vegetables are also excluded from certain eating plans. Dr. Joshi’s Holistic Detox — endorsed by Gwyneth Paltrow and Kate Moss — claims nightshades are related to poison ivy and potentially poisonous. “But poison ivy isn’t even in the same plant family,” explains Barry Micallef, a plant biochemistry expert at the University of Guelph. (What are lectins? Should you avoid them?)

Why the bad reputation? Some people may think nightshade vegetables are harmful because they’re confusing them with “deadly nightshade” or Atrope belladonna, an inedible weed that’s also part of the Solanaceae family, explains Micallef. Historically, the deadly nightshade has been associated with witchcraft. When ingested in large amounts, it may cause convulsions or even death. But that has nothing to do with these vegetables. Here, we bust four other myths:

1. Nightshades contribute to osteo­porosis

Doubtful. Certain macrobiotic diets recommend that people with health challenges avoid nightshade vegetables and that even healthy people should eat them infrequently, says Judy MacKenney, a counsellor at the Kushi Institute, a macrobiotic edu­cational institute in Becket, Mass. “Nightshade vegetables are high in oxalic acid,” she claims, “Which inhibits the absorption of calcium, and can weaken bones and lead to osteoporosis.” But Stephanie Atkinson, a member of the scientific advisory committee for Osteoporosis Canada, says that while oxalates are known to bind calcium in the intestine, reducing calcium absorption, this occurs only when calcium intakes are very low and oxalate intakes very high. Nightshades, however, are not high in oxalic acid, she says. “The alkali contributed by vege­tables and fruits is bene­ficial for bones as it protects them from using bone to neutralize blood acid.” Here’s the truth about how to reduce your risk of osteoporosis.

2. Nightshade vegetables contain a toxic alkaloid

Not true. Many alternative medi­cine websites allege that nightshade vegetables contain a toxic alkaloid compound called solanine, a defence mechanism in some Solanaceae plants that protects against natural threats such as insects. It’s true that solanine may develop in potatoes, which turn green when they are exposed to light during growth, says Micallef. (That’s why potatoes with green areas should be discarded.)

Contrary to the rumours, however, eggplant, peppers and tomatoes — even the green ones — do not produce solanine and are perfectly safe to eat, he says.

3. Nightshade vegetables worsen arthritis pain

Doubtful. Much of the online dis­cussion concerns nightshade vegetables and arthritis, and the notion that eating these vegetables causes an increase in pain or inflammation. But no scientific evidence supports that theory. “I’m not aware of any studies in peer-reviewed journals that prove or disprove that they affect arthritis,” says arthritis expert Mark Erwin, an assistant professor of orthopedic surgery at the University of Toronto. “There are a lot of references to it, but the evidence is mostly anecdotal.” There’s also no scientific reason to avoid nightshades even if you have arth­ritis, says Pamela Piotrowski, a registered dietitian at the Arthritis Society of Ontario. “Many people have food intolerances. If you start to feel achy every time you eat tomatoes, then maybe, for you, tomatoes are a contributing factor.” But even if your symptoms disappear after eliminating tomatoes, it would be hard to pinpoint that as the cause since many factors can affect arthritis.

4. They cause migraines

No. Linking nightshades to migraines is also without merit, according to Dr. Jonathan Gladstone, director of the Gladstone Headache Clinic and director of neurology at Cleveland Clinic Canada in Toronto. “I am certain that headache experts internationally would be in agreement that there is no evidence that tomatoes, peppers, eggplant and potatoes cause migraines,” he says.

The health benefits of nightshade vegetables “far outweigh any risks,” says Piotrowski. Tomatoes and peppers are amazing sources of antioxidants that lower the risk of cancer and heart disease; potatoes are high in vitamin C; and eggplant is a source of vitamin K. All are high in fibre. If you do want to elimin­ate them, make sure you get this nutritional value from other foods.

Looking to manage pain? You’re better of checking out these 23 science-backed natural home remedies for arthritis pain.

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