Plant leaves turning purple

Plant Deficiencies: Why Are Leaves Turning Reddish Purple In Color

Nutrient deficiencies in plants are hard to spot and are often misdiagnosed. Plant deficiencies are often encouraged by a number of factors including poor soil, insect damage, too much fertilizer, poor drainage or disease. When nutrients such as magnesium, calcium, potassium, phosphorus and nitrogen are lacking, plants respond in a variety of ways—oftentimes in the leaves.

Leaf problems in plants that are deficient in nutrients or trace minerals are common and may include stunted growth, drying and discoloration. Nutritional deficiencies present differently in plants, and a proper diagnosis is critical in order to rectify the problem. One of the most commonly asked questions relates to having a plant with purple leaves, or leaves turning reddish purple in color.

Why Are Plant Leaves Turning Purple?

When you notice a plant with purple leaves rather than the normal green color, it is most likely due to a phosphorus deficiency. All plants need phosphorus (P) in order to create energy, sugars and nucleic acids.

Young plants are more likely to display signs of phosphorus deficiency than older plants. If the soil is cool early in the growing season, a phosphorus deficiency may develop in some plants.

The underside of marigold and tomato plant leaves will turn purple with too little phosphorus while other plants will be stunted or turn a dull dark-green color.

Leaves Turning Reddish Purple in Color

Leaves turning reddish purple in color is most often seen in corn crops. Corn with a phosphorus deficiency will have narrow, bluish green leaves that eventually turn reddish purple. This problem occurs early in the season, often due to cold and wet soil.

Corn suffering from a lack of magnesium may also display a yellow streaking between the veins of lower leaves that turn red with time.

Other Causes for a Plant with Purple Leaves

If you have a plant with purple leaves, it may also be due to elevated levels of anthocyanin, which is a purple colored pigment. This pigment builds up when a plant becomes stressed and normal plant functions are interrupted. This problem can be very hard to diagnose as other factors can cause the pigment buildup such as cool temperatures, disease and drought.

By Jane E. Polston | Gary Vallad|February 1, 2009

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Red is the color most associated with tomato, but purpling in both fruit and leaves is also possible. While purple fruit is characteristic of certain cultivars, purple leaves are most often caused by stress or disease. In most people’s minds, purple tomato leaves are the result of nutritional deficiencies, primarily of phosphorus, nitrogen, or potassium. Since 2006, unusually large numbers of tomato plants with purple leaves have been observed in several tomato fields in Hillsborough, Manatee, and Miami-Dade counties. Foliar analysis of nearly 500 samples of purple and normal colored leaves showed that this purpling was not due to nutritional deficiencies. The disorder was named tomato purple leaf disorder (TPLD) and multiple studies were conducted by a task force to understand the disorder and to identify its cause. Following is a summary of what we know to date.

Symptoms Of TPLD
Initial symptoms of TPLD appear between six to eight weeks after transplanting and could be somewhat confused with mild phosphorus (P) deficiency. The key diagnostic difference between TPLD symptoms and the symptoms of P deficiency is that symptoms of P deficiency first appear on the lower leaf surface, causing vein purpling, and then extend to the whole leaf. By contrast, symptoms of TPLD appear primarily on the upper leaf surface, without affecting the veins, and gradually spread to the entire leaf surface.

Often, when one leaf overlaps another, TPLD only develops on the surface portion exposed to sunlight, with the shaded leaf tissues remaining green. No deformation or bronzing of the affected leaves has been observed. Instead, these leaves appear to senesce prematurely. The intensity of the purple color and the extent of purpling vary among leaves on the same plant, among plants of the same cultivar, and among cultivars. This disorder has been seen in all types of cultivated tomatoes (i.e. grape, cherry, round, and Roma types). Grape tomatoes seem to have the most severe symptoms. The effect of TPLD on yield is unknown.

Distribution And Incidence In Commercial Tomato Field

Initial studies in two affected fields in South Florida show that incidence of TPLD symptoms were less than 1% at 11 weeks after transplanting. However, four weeks later, incidence in the same field increased to more than 90%. At the same time, an adjacent field under the same management practices, which was four weeks younger than the previous field, exhibited less than 25% incidence. No clear pattern of distribution was observed with respect to incidence within a row or in relation to the prevailing sun and wind direction.

Searching For Answers

Many different tests for known pathogens of tomato using standard microbiological, serological, and nucleic acid-based methods were negative. This indicates that the causal agent is something new. The mechanism of transmission is still not known for sure, but greenhouse studies indicate that there is some transmissible agent. Some of the studies suggest that TPLD is caused by an infectious agent, like a virus or viroid. There is some evidence to suggest the presence of a virus similar to the whitefly-transmitted Tomato chlorosis virus. However, it is not clear if this virus is the cause of TPLD or is only part of the cause. There is some evidence that suggests a viroid may also play a role in the disorder. However, more research will be necessary to clarify the current results and confirm the identity of the causal agent.

Jane Polston is with the Dept. of Plant Pathology, University of Florida/IFAS, Gainesville.

See all author stories here.

Gary Vallad is an assistant professor of plant pathology at the UF/IFAS Gulf Coast Research and Education Center in Balm.

See all author stories here.

Tomato leaves turning purple

Based off these foliage photos, I don’t see evidence of a disease.
I think the plants may have been in the containers a little too long and so the root system is too small to support the foliage. This warm weather has everything moving along faster than previous cooler springs! The purpling indicates a possible nutrient issue. The plant will likely recover and grow new healthy foliage once planted in a larger container or in the ground and fertilized.
The rolling of the leaves is most likely a problem referred to as physiological leaf roll. It isn’t a disease but caused by the plants response to environmental conditions. Some tomato cultivars have been noted to be more prone to this than other cultivars. The small root system will likely be involved in this as irregular watering has been noted as a factor. The plants will grow and produce just fine. New leaf grow may or may not show that rolling. the only thing that might occur is that the fruit is prone to sunburn since it will be more exposed than if the leaves were flat and blocking the sun. Susceptibility to sunburn will vary depending on the cultivar.
OSU Extension has some resources that you might find useful:
Grow Your Own Tomatoes and Tomatillos
A much longer publication on Physiological Leaf Roll of Tomato
Hope this helps and thanks for using Ask An Expert!

Stems of cannabis plants turning purple, how do I fix this?

by Nebula Haze

Question: Help! My cannabis plants are young (growing in soil indoors with sunlight and my leaves are medium sized) yet my main stems are turning purple from the top downwards. Have you seen this before?

Answer: When a cannabis plant or seedling has a purple stem without any other signs of problems, it is often the result of genetics. However, sometimes you’ll see red stems (pictured right) which can sometimes be caused by stress, environment or pH problems.

Wait a week or two before making any alterations if your plant otherwise appears healthy and is growing fast.

If there are no other symptoms and the rest of the plant is growing fast and healthy, red stems usually aren’t a big deal. Often stems turn green on their own. As long as you’re continuing to take good care of your plant and responding quickly to any other problems, you should be okay.

These red stems were caused by transplant shock and overall stress, but the clone just needed some TLC and time to grow out of it.

Truely purple stems are often caused by genetics

If you believe there is a nutrient problem with your cannabis plant, for example if your plant is also growing slowly or the leaves are discolored, then the plant may be suffering from…

  • Incorrect pH – The pH being too high or too low at the roots is the most common reason to see purple or red stems! (or any deficiency)
  • Magnesium deficiency can cause purple stems. A good cannabis-friendly nutrient system has a significant amount of magnesium, but if you’re using very soft water, or RO water, you may need to add a Cal-Mag to your nutrient regimen.
  • Temperature – heat or especially cold can trigger red stems in some places
  • Humidity – very high or low humidity can stress plants (especially young seedlings)
  • Other types of stress such as light burn, transplant shock, or overwatering can trigger red stems
  • Sometimes you’ll never know why and plants just grow out of it 🙂

Jump to…

Cannabis plant problems by picture

7 Steps to Cure 99% of Cannabis Growing Problems

Cannabis Nutrients: Explained

How to germinate cannabis seeds

Cannabis Nutrient and Deficiency Table

NITROGEN (N)

Symptoms of Nitrogen deficiency include; red stems, small growth, pale appearance to the plant, and a rapid yellowing of the lower leaves that spreads up the plant. To remedy this particular situation, simply add a organic fertilizer containing nitrogen and monitor.

Symptoms of Nitrogen deficiency include; red stems, small growth, pale appearance to the plant, and a rapid yellowing of the lower leaves that spreads up the plant. To remedy this particular situation, simply add a organic fertilizer containing nitrogen and monitor.

PHOSPHOROUS (P)

Phosphorous deficiency symptoms include; red stems and slow, stunted, or deformed growth but also include darker green lower leaves as well as leaves that may yellow then die. Adding a organic fertilizer containing Phosphorous can fix this problem but, while improvement to damaged areas may not show, newer growth will appear normal.

Phosphorous deficiency symptoms include; red stems and slow, stunted, or deformed growth but also include darker green lower leaves as well as leaves that may yellow then die. Adding a organic fertilizer containing Phosphorous can fix this problem but, while improvement to damaged areas may not show, newer growth will appear normal.

POTASSIUM (K)

Another issue similar to Nitrogen and Phosphorous deficiencies, Potassium deficiency has similar symptoms and include, curling of leaf ends as they die and stretching of the plant. This can be cured by adding a organic fertilizer containing Potassium. Another fix would be to flush the plant with water and half the normal amount of a balanced NPK (Nitrogen, Phosphorous, Potassium) nutrient solution.

Another issue similar to Nitrogen and Phosphorous deficiencies, Potassium deficiency has similar symptoms and include, curling of leaf ends as they die and stretching of the plant. This can be cured by adding a organic fertilizer containing Potassium. Another fix would be to flush the plant with water and half the normal amount of a balanced NPK (Nitrogen, Phosphorous, Potassium) nutrient solution.

CALCIUM (CA)

Plants lacking Calcium balance can result in the soil becoming too acidic. Calcium deficiency can be fixed by foliar feeding (adding liquid fertilizer directly to plant leaves) one teaspoon of dolomatic lime per quart of water until the plant’s condition approves.

Plants lacking Calcium balance can result in the soil becoming too acidic. Calcium deficiency can be fixed by foliar feeding (adding liquid fertilizer directly to plant leaves) one teaspoon of dolomatic lime per quart of water until the plant’s condition approves.

SULPHUR (S)

If the new growth of a plant contains yellowing, it is probably suffering from Sulfur deficiency. This deficiency can be cured by mixing one tablespoon of Epsom salts per gallon of water until the plant’s condition improves.

If the new growth of a plant contains yellowing, it is probably suffering from Sulfur deficiency. This deficiency can be cured by mixing one tablespoon of Epsom salts per gallon of water until the plant’s condition improves.

MAGNESIUM (MG)

Magnesium deficiency usually starts in the middle of the plant and spreads to the younger leaves. Leaves turning yellow, or even white, with the veins remaining dark green is the best indicator of Magnesium deficiency and can best be cured by spraying with a 2 percent Epsom salt solution.

Magnesium deficiency usually starts in the middle of the plant and spreads to the younger leaves. Leaves turning yellow, or even white, with the veins remaining dark green is the best indicator of Magnesium deficiency and can best be cured by spraying with a 2 percent Epsom salt solution.

IRON (Fe)

Pale leaves with dark green veins are indicative of Iron deficiency and can be fixed by foliar feeding with a organic fertilizer containing Iron.

Pale leaves with dark green veins are indicative of Iron deficiency and can be fixed by foliar feeding with a organic fertilizer containing Iron.

MANGANESE (Mn)

When large amounts of Magnesium are present in the soil, yellow or necrotic (dying or dead) spots will occur on the upper leaves. To cure, foliar feed with chemical fertilizer containing Manganese.

When large amounts of Magnesium are present in the soil, yellow or necrotic (dying or dead) spots will occur on the upper leaves. To cure, foliar feed with chemical fertilizer containing Manganese.

BORON (B)

Dead or greying shoots that appear burnt are indicative of Boron deficiency and can be treated with one teaspoon of Boric acid per gallon of water.

Dead or greying shoots that appear burnt are indicative of Boron deficiency and can be treated with one teaspoon of Boric acid per gallon of water.

MOLYBDENUM (Mo)

Mo deficiency includes yellowing of middle leaves and can be treated by adding organic fertilizer containing Molybdenum.

Mo deficiency includes yellowing of middle leaves and can be treated by adding organic fertilizer containing Molybdenum.

ZINC (Zn)

When white areas form at leaf tips or in between veins, the plant is Zinc deficient. This can be treated by adding organic fertilizer containing Zinc or by burying galvanized nails in the soil.

When white areas form at leaf tips or in between veins, the plant is Zinc deficient. This can be treated by adding organic fertilizer containing Zinc or by burying galvanized nails in the soil.

OVER FERTILIZATION

Indicated by yellow or burnt leaf tips, Over Fertilization can be fixed by flushing 3 gallons of water per every gallon of soil.

Indicated by yellow or burnt leaf tips, Over Fertilization can be fixed by flushing 3 gallons of water per every gallon of soil.

A deficiency in a macro-nutrient (an element plants need in large amounts) can manifest in a marijuana plant under poor growing conditions or stress (overwatering, overheating, transplanting, etc.) and it’s important that cannabis growers know how to identify different ones. To give you an idea of what to look for, here we talk about how to identify some of the most common macro-nutrient deficiencies in cannabis plants.

  • Calcium (CA)
    A lack of Calcium in cannabis plants pervents flowers from fully developing, weakens their ability to take the heat, and eventually causes the soil to turn too acidic to support healthy root growth. Calcium deficiencies show up in the newest vegetation as stunted or deformed growth, leaf curling or die-off, flimsy or hollow stems, and distorted or discolored leaves.
  • Nitrogen (N)
    You can identify a Nitrogen deficiency in cannabis plants by the red stems that develop and the quick yellowing of the older, lower leaves that spreads upwards. Other symptoms includ stunted growth, a pale overall appearance, and leaves that wilt, curl, turn brown, and eventually die.
  • Phosphorous (P)
    You can tell that a marijuana plant had a Phosphorous deficiency by the dark shade of shiny green lower eaves turn and the blue, purple, or bronze spots that appear on them. You’ll also see slowed or deformed growth, bright red or purple colored stems, and leaves that curl, thicken and feel stiff before turning brown or yellow and falling off.
  • Potassium (K)
    A cannabis plant with a Potassium deficiency shows symptoms like stretched, spindly growth as well as top and bottom leaves that turn brown. The leaves also exhibit burnt, curling edges with yellowing margins.
  • Sulfer (S)
    You can identify a lack of Sulfer in your cannabis plant apart from other nutrient deficiences that cause chlorosis (yellowing of leaves) by the fact that it begins at the leaf base rather than the tips. It affects the plant all over (starting with the newest growth), and the underside of leaves may turn pink, red, or orange.
  • Magnesium (MG)
    Signs of a magnesium deficiency start in the middle of cannabis plants and spread to the new growth; the leaves turn light green, yellow, or even white while the edges and viens remain dark green.

A few weeks ago, the Epi kitchen was knee-deep in pickling jars and we noticed something weird: all the pickled garlic had turned blue. Shocked, we reached out to some food scientists to figure out what the heck was going on.

Turns out, the scientists are nearly as stumped as we were when it comes to blue garlic. “We don’t know a lot about this,” says Dr. Luke LaBorde of Penn State University’s Department of Food Science. “It’s definitely enzymatic and nonenzymatic reactions occurring in the garlic, but we really don’t know entirely why.” Only a few papers have been written on the subject, but it’s not as if the study of color-changing garlic is a booming field.

As far as they can tell, garlic enzymes—which give it that distinct flavor—break down over time. Naturally occurring sulfur in the garlic interacts with those enzymes, occasionally turning it slightly green or blue. Sometimes the color change happens, sometimes it doesn’t. Shifts in temperature, pH, and the age of the garlic can also come into play, so heating it or mixing it with acid might have some affect.

Which means blue garlic is not just a pickling problem. Anytime you cook garlic or onions in a high-acid solution—say you sauté them, then deglaze the pan with lemon juice—this issue could occur. It also might happen simply by storing garlic for too long.

If you want to avoid the smurf coloration, using fresh garlic is your best best, says LaBorde. Older garlic apparently colors more often. In fact, in China, where a pickled garlic called Laba is prized for its green and blue color, garlic is aged for several months to increase the coloration.

LaBorde also suggests blanching: “Try putting them in hot water for a short period of time, which might slow down or inactivate the enzymes.”

The good news is, the color doesn’t affect the taste or safety of the garlic. “Nothing suggests the color affects the taste or flavor of the food,” says LaBorde. “You’re just rearranging some molecules inside the garlic. Even if it’s blue, it should be okay.”

Growing the best bulb: tips for great garlic

There is a big demand in Australia for varieties of purple garlic. Image:

Getty Images: Bernard Van Berg

There is a big demand in Australia for varieties of purple garlic.

Image:

Getty Images: Bernard Van Berg

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Australians love garlic, and are increasingly turning away from chemically-treated Chinese imports. But what is the key to growing the best bulb? Maria Tickle learns patience is the trick.

I remember the day clearly. The day that has become known in our household as the Great Garlic Disaster.

People are recognising how fabulous Australian-grown garlic is, the health benefits of it, the different flavours and exactly what we have available.

It was a warm, sunny Sunday afternoon and my five-year-old was helping me harvest the organic garlic I had planted and carefully nurtured for eight long months.

I am a not fan of delayed gratification, which is a given growing garlic, but I was tired of the rubbery cloves of imported garlic on sale at the supermarket and had decided to grow my own.

As per harvesting homegrown tomatoes, I was quietly excited about something fresh and tasty for a change.

I had moved onto weeding and had my back to Miss Five.

She was being very quiet until she proudly declared: ‘ I’m finished!’

Finished what?

I turned around to see that she had diligently washed every single garlic bulb in a bucket of muddy water. In return she learned a few new swear words. Despite my best efforts to dry them—windowsill, low oven—many of the cloves went rubbery and mouldy. Heartbreaking.

According to botanist Penny Woodward, author of Garlic, I’m on the right track despite a bad start.

According to Woodward, we should all be growing our own garlic, or at the very least sourcing Australian-grown garlic, and not just from farmers’ markets.

Woodward, a board member of the Australian Garlic Industry Association, is on a mission to make locally grown garlic available in supermarkets year-round.

‘We used to grow it year-round, or came really close to it. We had more than 600 growers in Australia in the mid-’90s, and Chinese garlic was brought in,’ she says.

‘The tariffs were reduced, and cheap Chinese garlic came, and we ended up with about 13 growers, just because they couldn’t compete with Chinese prices.

‘But now that people are recognising how fabulous Australian-grown garlic is, the health benefits of it, the different flavours and exactly what we have available, people are prepared to pay a little bit more for good garlic.’

Flavour aside, there’s another reason Penny is pushing to increase the supply of Australian garlic.

‘All imported garlic, under Australian customs regulations, is sprayed with methyl bromide, which is a toxic biocide,’ she says.

‘It is part of not spreading diseases to crops in Australia, so it actually protects the garlic industry.

While its use is tightly controlled because it is such an effective ozone depleter, the Federal Department of Agriculture says that in the dilutions used, methyl bromide is safe, even for those workers who handle it.

Woodward concedes that ‘it’s probably not harmful to the individual, but being an organic grower and an organic committed person, I wouldn’t use it’.

Organic garlic grown on a farm in Griffith, NSW. Image:

Laurissa Smith, ABC Rural

Organic garlic grown on a farm in Griffith, NSW.

Image:

Laurissa Smith, ABC Rural

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She says we should be also encouraging our farmers to plant many different varieties of garlic.

‘There are probably 100 different cultivars of garlic available in Australia and we are just trying to identify them now. We probably won’t get good identification until we can DNA test them all, because growers keep changing the names.

‘So something that was identified as New Zealand Purple when it first got here then became Tasmanian Purple then Flinders Island Purple, and they are basically all the same.’

Penny breaks open a Creole garlic called Spanish roja, exposing the beautifully-coloured cloves inside and another called festival that has an even darker coloured clove.

‘These garlics were harvested in November last year, so they have stored for nearly eight or nine months,’ says Woodward. ‘They will actually store for more than 12 months. I’ve had one store for 18 months.

‘We need to be growing more of these garlics. Chefs call them rosy garlic sometimes, and a lot of them are quite hot.’

And if you’ve ever wondered why your mum told you to bash the garlic clove with the side of a knife before using it, it turns out the reason is quite scientific.

‘There’s a chemical in garlic called alliin, and when it’s in the presence of the enzyme alliinase it turns into allicin. So you only get the allicin once you actually cut or bruise or crush the clove, and the more finely it’s cut or bruised or crushed, the stronger the allicin.

‘That gives garlic all its flavour, and it’s from that that you get the various chemicals as it breaks down. So if you cook garlic you get diallyl disulfide, which is why cooked garlic tastes different to fresh garlic.

‘As it breaks down and goes through your body, quite often it is hydrogen sulphide that is produced. There’s a whole book about garlic chemistry.’

When to plant your garlic

I was once told to plant garlic on the shortest day of the year and harvest it on the longest, but obviously I haven’t been watching enough Gardening Australia. According to Woodward I have it all wrong—that only works if you live in Europe.

‘In Australia you plant from February if you are in Queensland with the really early cultivars, to late May in Tasmania and harvest six to eight months later,’ she says.

Woodward says the garlic cultivars that are easiest to grow and keep well are the Tasmanian purple and festival, and it’s best to harvest garlic when the leaves start to die back.

‘With onions, you wait until they are all dead, with garlic you need four, five, six leaves still left on it because those leaves form the skins around the bulb.

‘Then you pull the soil back from a couple of your bulbs, and if you’ve got decent-sized bulbs and you can feel the clove ridges on the bulbs, then they are pretty close to being harvested.

‘You can stop watering at that point and then dig them up a week to two weeks later depending on how hot it is.’

The delayed gratification that comes with garlic continues, because you then have to cure the bulbs. All that garlic you see hanging around kitchens isn’t just to ward off vampires.

‘You can actually eat garlic at any point from the time it sprouts to the time that you harvest it, and that is known as green garlic or garlic sprouts or spring garlic, but it doesn’t have the complexity of flavour of the cured garlic,’ says Woodward.

‘To cure garlic, you hang it for between four and six weeks out of direct light, somewhere where there is good air movement.’

Not one to give up easily, I again planted a stash of garlic, but this year I will be hiding all the buckets, harvesting alone and hanging them very, very high.

  • Tips for growing garlic

    Listen to the full discussion on Blueprint for Living.

Blueprint for Living is a weekly rummage through the essential cultural ingredients—design, architecture, food, travel, fashion—for a good life.

Most of the plants you see on a daily basis are green, but every so often you might happen upon the odd purple-leafed tree or shrub. Why do some plants have these purple parts?

The answer lies with another “P” word: pigment. Green plants contain a lot of the pigment chlorophyll. Because chlorophyll molecules are very good at soaking up blue and red light — but not so good at absorbing green light — plants containing a lot of chlorophyll appear green to the human eye.

Pigment is also behind a purple plant’s vivid coloring. Plants that appear purple, blue or red contain a higher concentration of anthocyanin than chlorophyll. Anthocyanin is a pigment adept at absorbing green light, but less skilled at absorbing red, blue or purple light.

Scientists believe that the purple leaves on some plants — like Persian shield, oyster plant and ornamental cabbage — may act as a natural “sunscreen,” protecting the cells of the plant from too much light. Plants that experience too much sunlight can suffer from photoinhibition, a reduction in the plant’s ability to carry out photosynthesis.

And because high levels of anthocyanin often appear together with high concentrations of poisonous phenols, it’s possible that the purple leaves of some plants help ward off hungry herbivores.

Follow Elizabeth Palermo on Twitter @techEpalermo or on Google+. Follow LiveScience @livescience. We’re also on Facebook& Google+.

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