- Pests are eating our rhubarb leaves!
- Rhubarb-PestsRhubarb Crown Root Rot
- PESTS AND DISEASES AFFECTING RHUBARB
- CROWN ROT
- RHUBARB LEAF DAMAGE
- WEAK GROWTH, YELLOW LEAVES
- RED EDGED LEAVES
- ORANGE / RED SPOTS ON RHUBARB LEAVES / STALKS
- HOLES IN RHUBARB STALKS
- Rhubarb Diseases
- Rhubarb Plant Diseases and What to Do
- How to Grow Rhubarb: Diseases, Harvesting and Recipes
- Dreaming of a beautiful, productive veggie garden?
- Growing rhubarb in Western Australia
- Climate and soils
- Propagation and planting
- Growing the crop
- Harvesting the crop
- Rhubarb Pests
- Why Do Rhubarb Leaves Work To Repel Insects and Pests?
- How To Make Pesticide From Rhubarb Leaves
- How Long Can You Keep The Insecticide Spray?
- Should You Use The Spray On Plants Grown For Food?
- Rhubarb Plants Turning Yellow
- some of my rhubarb leaves are turning yellow, should I pick the larger leaves, and leave the smaller ones alone?
Pests are eating our rhubarb leaves!
Thank you for sending the pictures. From those, it looks like there are two issues facing your rhubarb. The ragged holes in the leaves look like they could be from slugs. The wilted leaves and stems in the center suggest a disease problem. There are a couple of diseases that strike rhubarb (http://www.ipm.iastate.edu/ipm/hortnews/1995/6-30-1995/rhub.html). Unusually wet weather can promote disease outbreaks. I apologize that I can’t provide a definitive diagnosis, but you can take a sample toyour local extension office for their advice. If a picture is worth a thousand words, an actual plant is priceless.
If you decide to remove the plant, do not replant in the same location as the pathogen can linger in the soil and plant debris to infect a new plant.
Many diseases can be prevented by keeping the site clear of old plant debris and avoiding the build up of moisture on the ground and humidity in the plant canopy. To keep the leaves from staying wet, water at the base of the plant rather than using overhead irrigation, and try not to over irrigate so the soil stays too wet. Moist soil and plant conditions also provide a favorable habitat for slugs. Try to keep old fallen leaves and plant debris cleared from the area as this sanitation effort will reduce the chance for disease spread and help control pests like slugs.
Rhubarb-PestsRhubarb Crown Root Rot
Deter rhubarb-pests like aphids and potato-bugs from destroying your garden with some preventative action. Knowing how to fight some of the common problems beforehand can save a lot of grief.
Rhubarb growers face the same general dilemmas as any other gardener.
Potato-bugs, beetles and many other plant insects can become quite a nuisance. These bugs lay their eggs on the rhubarb stalks and stems. Eventually they begin to feed on the leaves. You will notice the leaves will become wilted and probably full of holes.
Slugs can be a problem in areas that are weedy and have poor drainage.
You can begin to solve this problem by keeping your garden area well weeded. The weeds are one reason that attracts the bugs in the first place.
Insect problems can result also by having your rhubarb too close to your other garden plants which could be infested which is another good reason to plant your rhubarb off by itself in the far end of your garden.
The bugs can be picked off the plant by hand, or simply take a spray bottle of mild soap and water and give them a light misting.
Snout beetles burrow into your roots, crowns and stalks. You must treat with insecticide and/or burn badly infected stalks after these rhubarb-pests lay eggs usually in July.
Fungus growth can occur on the crowns and stems resulting in rot.
This is due to overly humid conditions and poor air circulation. You will see spots on the leaves and possibly holes in the leaves as well.
Remove the affected leaves from the stems and apply a fungicide as directed.
A serious crown root rot caused by fungus is called Foot Rot.
These plants have to be dug and discarded. The best idea would be to relocate your rhubarb bed if the area does not dry up.
Red Leaf disease is found in Western Canada, and it is not known what causes it. The leaves become reddish and wilt quickly. New leaves do not grow. Decay is prevalent below the ground in the centers of what looks like healthy roots.
These plants must be removed immediately, and new plants should never be replanted in this area.
So, keep an eye out for unwanted bugs and slugs, and signs of leaf decay. Establish a weed control schedule.
Water only as necessary.
Let your rhubarb garden breath by giving it the space it needs.
AN OUNCE OF PREVENTION IS WORTH A POUND OF CURE!
Make sure you have rhubarb for next year!
If you have flowers close by your vegetable garden, keep an eye on those as well. Everything interacts. Aphids actually love roses too and should be checked periodically.
For some wonderful information on pest control and overall care of your rose garden, see this site.
Rose Gardening Made Easy
How To Get Rid of the Slugs
Rhubarb-Curculio, These You Don’t Want
Control those Rhubarb-Pests
With a Simple Aphid Spray.
Whether you’re an organic garden newbie, or an inexperienced gardener this great site will provide you with the latest time-tested information on Organic Gardening and Organic Pest Control. Check it out!
Organic Garden Info
Return To Home Page
Have your say about this topic. Leave me a comment in the box below. By Jane Orr Copyright 2007-2013 Savor-The-Rhubarb.com
PESTS AND DISEASES AFFECTING RHUBARB
This is easily identified because as the name suggests, the crown of the rhubarb ((the central woody bit) rots! After a couple of weeks it will literally turn to mush and die away. The stalks and leaves are also killed.
The cause is a variety of fungi attacking the plant. In normal growing conditions this won’t happen but when the soil becomes very wet and waterlogged this encourages the fungi to flourish. There is no cure, the entire plant should be dug up and burnt, don’t put it on the compost heap. The fungi will remain in the soil for a few years so if you plan to plant replacement rhubarb, and don’t want crown rot, then plant them in a different place in your garden.
A major factor which will increase the risk of crown rot is having the central part of the plant infested with weeds or anything which covers the crown. This will encourage excessive moisture retention and also slug damage which will allow fungi to enter the crown surface. Although rhubarb often grows well when ignored, it is best kept weed free.
RHUBARB LEAF DAMAGE
It’s very common for rhubarb leaves to be attacked by slugs and snails. They leave a patchwork of holes in the leaves but don’t cause any other damage. We strongly suggest that you don’t use any pellets or other chemicals unless the damage is very severe.
Most rhubarb plants will survive slug and snail damage easily and as the leaves get older in the season the slugs and snails will leave them alone – they prefer younger leaves near the ground.
Although we don’t recommend chemicals for slugs and snails on rhubarb, there are a couple of things you can do to reduce the problem.
First, keep the area around your rhubarb clear of weeds and other debris – both of those provide an ideal environment for slugs and snails.
Keep a look out for slugs and snails around the central base of the plant and dispose of them whenever you see them. This will go a long way to keeping your rhubarb free from leaf damage.
WEAK GROWTH, YELLOW LEAVES
Occasionally rhubarb will show signs of below normal growth and this may also be accompanied by yellowing leaves. This is unlikely to be a pest or disease but much more likely to be something in its environment which is causing a problem.
If the soil is light or sandy your plant may not be getting enough nutrients. Rhubarb loves lots of plant food so that is definitely a solution worth considering. A couple of handfuls of blood, fish and bone fertiliser spread around each plant in February and August time will provide them with a good source of nutrients.
They also like lots of moisture in the summer, not waterlogged but moist soil. A full sun position can sometimes be a problem, especially in warmer parts of the UK. Rhubarb grows best in partial shade especially from June to August.
If you “force” your rhubarb, don’t do this on the same plant two years running. Forcing rhubarb weakens the plant and if you do this two years in a row the plant will definitely suffer and show signs of weak growth.
Finally, don’t harvest rhubarb stalks in the first year and only take a few in the next year. Harvesting too many stalks reduces the amount of leaves and these are the plant’s major source of harvesting and making use of sunlight.
RED EDGED LEAVES
This normally occurs late in the rhubarb year (after all, they get an early start!) when the leaves are beginning to think about dying down, typically in July onwards. See the picture below sent in by one of our readers which illustrates this perfectly.
Picture courtesy of Rosemary G
It looks quite dramatic on some leaves and may cause concern but it’s all natural. Those red colours are present in the leaves most of the time but the chlorophyll (used to convert sunlight to energy) in the leaves hides the red and gives them their green colour. As the season progresses some leaves decide to start shutting down for winter and use the energy stored in the rhubarb crown as the key source of energy.
As they shut down they produce less chlorophyll and that exposes the red colouring in the leaves. It’s most apparent in older leaves, as in the picture above, and it starts at the edges of the leaves and slowly moves inwards. Not all leaves are affected and different varieties of rhubarb are affected more than others.
Rhubarb grown in full sun is also more likely have red leaves because they have more residual glucose in them compared to rhubarb grown in part or full shade.
ORANGE / RED SPOTS ON RHUBARB LEAVES / STALKS
The spots are the fungus called rust which are most common on the leaves but they can also infect the stems of rhubarb. The fungus thrives in moist conditions where air-flow is restricted. It does not damage the crown although the crown can be weakened if the leaves are badly infected and cannot photosynthesise correctly.
To prevent and minimise the effects of rust on rhubarb do the following:
- Remove badly infected leaves and stems although those with only mild symptoms can be left on the plant. Destroy badly infected leaves and stems, do not put them on the compost heap.
- Clear all vegetation around the rhubarb plant to allow maximum air flow through it.
- Do not feed the plants with nitrogen based fertiliser which would only encourage soft, leafy growth which is susceptible to rust.
- The key action you can take to avoid rust recurring in the next year is based on the fact that rust requires vegetation to exist. When the stems die down remove all trace of them and any other vegetation around the crown. This includes leaves and any other debris which is present.
HOLES IN RHUBARB STALKS
This is best illustrated by the picture below showing the cut end of a rhubarb stalk. There are hollow holes running up the centre of the stalk.
Rhubarb stalk with holes in the centre
This is typical of rhubarb stalks which have been picked when they are past their best. The stalk is beginning to deteriorate form the inside and is useless for eating. Rhubarb should be picked when it is young and tender. Leaving it too late to pick results in a very stringy texture and unpleasant taste.
Rhubarb Plant Diseases and What to Do
Rhubarb diseases are not very common due to the fact that rhubarb is a hardy, resistant garden plant.
There are a very few rhubarb diseases, mostly fungi (see pictures below), which may affect rhubarb.
Most of these fungi can be avoided by planting rhubarb in well drained soil.
If your soil is poorly draining soil you can mix it with organic matter and sand.
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Rhubarb Leaf Spots Caused by a Fungus
Wondering what the red spots are on the rhubarb leaves, is this a rhubarb disease?
Red Spots on the leaves of the rhubarb plants is something that I do find from time to time (see image above).
Most often this has not affected the actual rhubarb stalks at all. I pick/harvest the rhubarb stalks and discard the leaves immediately so as not to allow the fungi (see explanation below) to spread.
In most cases, unless the stalks are affected, there is NO need to discard the plants.
Here are examples of diseases and problems that may affect rhubarb plants:
Leaf Spots – Ramularia and Ascochyta (Fungi)
Ramularia rhei and Ascochyta rhei are two different pathogenic fungi that cause leaf spots in Rhubarb plants. In fact, rhubarb is the main host plant for these two fungi.
Ascochyta leaf spot – leaf infection first appears as small, green-yellow, irregular spots less than one half inch in diameter on the upper leaf surface. The leaf develops a mosaic appearance as the lesions unite. Later, the spots develop white centers surrounded by reddish margins, bordered by a grey-green zone. In a few days, the infected spots turn brown, die, and fall out, producing a “shot-hole” appearance. Aschochyta does not cause stalk infections.
Ramularia leaf spot – leaf infection first appears as small red dots that gradually enlarge to form circular lesions a half-inch or more in diameter. Larger spots become white to tan with purplish halos. The larger spots turn tan in color and become sunken lesions in the stalk tissue. Stalk infections occur later, appearing as small spots that elongate as the stalk grows. White fungus develops in the centers of spots on both leaves and stalks, becoming brown as the tissue dies. Stalk infection is a key symptom of ramularia infection.
Information Cited from: University of Minnesota Extension
Fungi on Rhubarb Leaves
Fungi overwinter in infected plant debris and in infected propagation stock.
To prevent and control these fungi always remove and destroy the rhubarb leaves which have not been harvested prior to the first heavy frost.
At any time when harvesting rhubarb, remove stalks with spotted leaves first.
Do not over-water the rhubarb, and if possible water only the soil (instead of over-head watering). Water early in the day to allow the leaves to dry by afternoon.
Also, do not put composted rhubarb leaves back on your rhubarb garden. By doing so you may be infecting the garden with fungi.
It is also possible to apply fungicides for control. Check with your local garden center for the best product to use.
This fungus may cause leaf, stalk, and crown rot, most often affecting forced rhubarb (covered rhubarb). This disease is more common in areas where rhubarb plants do not receive proper air circulation and high humidity.
To prevent this fungus, ensure there is no rotting material near the rhubarb plants, and apply a fungicide as soon as you notice the disease, and at 7 day intervals, or as recommended by a professional at your garden center.
Root and Crown Rots (fungi and bacteria)
Rhubarb plants affected by fungi and bacteria causing root and crown rots show a lack of ability to thrive. Leaves may turn yellow to red and collapse. The crowns, when examined, exhibit a brown-black decay. Large roots lack the characteristic small feeder roots. The larger roots may have large brown-black hole damage.
To help prevent this root and crown rot disease, be sure to purchase, (or otherwise acquire), healthy propagation rhubarb plant stock.
Plant rhubarb in gardens with well drained soil, and remove and destroy plants that exhibit disease, as soon as it is noticed. This will prevent the spread of the root and crown rot.
Anthracnose Stalk Rot
This disease problem with rhubarb may be more common after an unusually “wet” Spring, or when the plants are under another type of environmental “stress”.
The early indication of this disease is wilted leaves and large water-soaked lesions on the stalks. The lesions increase in size and eventually they turn black. The stalks may also look twisted and, eventually the whole stalk may collapse.
To help control this disease it is important to practice good garden “sanitation”, by removing and disposing of infected stalks as soon as the disease is evident. Also, be sure to harvest all of the stalks prior to the first frost of the Season, and, any stalks that are still on the plant after frost should be removed because this disease over-winters in infected plant tissue.
It is also important to ensure that the affected plants are well fertilized as soon as growth appears the following Spring, and again after the harvest is complete. Since this problem is more prevalent among plants that are stressed, fertilizing to provide optimal growing conditions should decrease injury caused by disease.
There are several viruses which are known to occur in rhubarb. If a rhubarb plant is affected by a virus it may show signs such as ring spots on the rhubarb leaves.
To help prevent rhubarb viruses, be sure to acquire healthy rhubarb plant stock, and avoid planting virus free crowns near virus contaminated crowns, so as not to allow the virus to spread to the healthy plants.
I have never, (over 30 years!), treated my rhubarb plants for any rhubarb disease.
What do my rhubarb plants look like then?
The leaves of my rhubarb plants are often dotted with small holes (usually due to plant pests), but the leaves are discarded when the stalks are harvested.
Unless there is a major infestation of rhubarb pests, or an major issue with fungi affecting your rhubarb plants, you will probably find that treating your rhubarb for rhubarb disease is not usually necessary.
I cannot think of an easier, and hardier vegetable to plant in your garden than rhubarb.
And it is a thrifty vegetable too!
No need to purchase seed each year, very little care required, and a HUGE harvest, a few times a season!
Vegetable gardening doesn’t get much easier than that!
Every property can accommodate a rhubarb garden … it really does grow like a weed!
Below are additional pages on this website with helpful information about growing rhubarb in the home garden, or use the website navigation bars.
HOW TO GROW Rhubarb
Rhubarb PLANT CARE
Rhubarb COMPANION Gardening
More COMPANION Plant Ideas
LINKS RELATED TO RHUBARB GARDENING
ORGANIC PESTICIDE RECIPES and Information
EASIEST Vegetable to GROW
CONTAINER GARDENING – Can Rhubarb be Grown in Containers/Pots?
Yorkshire FORCED RHUBARB
How to GET RID OF SLUGS
Natural WEED Control Tips
WHERE to Grow Rhubarb
TOP of Rhubarb Diseases
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How to Grow Rhubarb: Diseases, Harvesting and Recipes
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By Teresa Flora – In much of North America, spring is welcomed with the tart and tangy taste of fresh rhubarb. Rhubarb is one of the easiest and most rewarding perennials. There are just a few rhubarb diseases and pests to consider. It is technically a vegetable; however, it is used as a versatile fruit. For this reason, early settlers called it “pie plant.”
The earliest records of this easy-to-grow perennial date from about 2700 B.C. The Chinese used it for medicinal purposes then (and still do). It was much later that rhubarb was introduced into Europe. Records show cultivation at Padua, Italy around 1608. Twenty-five years later, seeds were obtained for planting in England. It was the 1770s before it was definitely recorded as a food there, used for making tarts and pies. A gardener in Maine got rhubarb from Europe about 1800 and introduced it to market gardeners in Massachusetts. In 1822, it was generally grown and marketed in Massachusetts. It was listed in an American seed catalog in 1828. As the pioneers moved westward, rhubarb went with them. “Pie plant” was easy to move and quicker to establish in a new location than fruit trees.
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McDonald, Valentine and Victoria are popular varieties today. However, a friend or relative who has rhubarb will probably be glad to divide theirs with you. Hills should be divided every three to four years. Slender stalks show a need for division or feeding.
Rhubarb can be divided in the spring or fall. Use the shovel to cut the old root into pieces with two or three buds at the top. Plants that are divided in the fall should be heavily mulched for winter protection. Plant in well-drained, fertile soil. Set roots in holes six inches deep and two feet apart, with crowns just below the surface. If you live in an area with hot, dry summers such as we have here in central Kansas, you can plant rhubarb where it will get partial shade. You must live in an area where the ground freezes to a depth of several inches in the winter in order to grow rhubarb.
Rhubarb should be harvested only lightly the second and third years, until the roots are well established. An established patch will often last 25 years or more. Rhubarb stalks should be pulled instead of cut. Cutting encourages rhubarb diseases and insect infestations. Use only the stalk as food. Rhubarb leaves contain oxalic acid, which is poisonous. Never use them for food. (Ed. note: Don’t feed the leaves to animals, either.)
Top dress with a heavy application of organic matter in either early spring or late fall. Organic matter applied over the hills during early spring hastens growth by forcing the plant. Remove seed stalks as soon as they appear to prevent them from draining the plant. You can expect a yield of three to five pounds per plant. If established plants receive plenty of moisture, they can be harvested until late summer.
If you are adventurous and have no use for the divisions you make in the fall, you can keep them for forcing indoors. After digging the roots in the fall, put them in a box filled with peat moss or sawdust. Store in a dark place in the cellar. In January, soak the peat moss or sawdust with water. Keep the box cool and dark. In a few days, the rhubarb will send out little stalks. They look a little like asparagus shoots, because they have no leaves. They taste great! Thaw some frozen strawberries, mix in the rhubarb shoots, and make an easy pie recipe for strawberry-rhubarb pie. Roots that are forced indoors will not produce well if planted outdoors in the spring.
Rhubarb Diseases and Rhubarb Pests
When growing rhubarb, diseases and insects shouldn’t be a major concern, but there are a few that should be mentioned. Crown rot is a rhubarb disease for which there is no cure. The plant begins to yellow and then collapses. Dig and burn the roots, being careful not to scatter infected soil. Do not plant rhubarb back into the same location.
Anthracnose attacks all parts of the plant above the ground. Examine stalks for watery spots which enlarge as the rhubarb disease progresses, Leaves will wilt and die. As soon as you spot this rhubarb disease, apply a fixed copper or sulfur-based fungicide every seven to 10 days. Do not harvest for three to four weeks after application.
Leaf spot has symptoms similar to anthracnose. Spots first appear water-soaked and then grow in size and take on a brownish or purplish-gray color. It cannot be cured. Plants affected by leaf spot should be removed and destroyed.
Plants with verticillium wilt are often affected early in rhubarb season with yellow leaves. The beginning of this rhubarb disease is often mistaken for a nutrient deficiency. Then as the rhubarb disease progresses, the yellowed leaves wilt and the edges and veins of the leaves die. Remove and destroy plants.
A rhubarb pest known as curculio is a 1/2 to 3/4- inch long yellowish beetle with a sucking snout. They bore holes and lay eggs in the stalk and cause black spots to appear. Hand pick them off as sprays do not seem to control the. Destroying dockweed near rhubarb may be helpful in controlling curculios.
Leaves of plants affected by spider mites become yellow and dry, or have pale yellow spots caused by mites sucking chlorophyll out of the leaves. They also inject toxins into the leaves, which discolor and distort them. When you suspect this problem, look at the undersides of the leaves. If you see what appears to be a tiny red, brown, or black speck of dirt, touch it. If it moves, it’s most likely a mite. Spray plants with a forceful spray of water three times, every other day, to knock mites off. If that doesn’t do the job, spray the undersides of leaves with insecticidal soap at least three times at five- to seven-day intervals.
Plants infected with whitefly appear to have dandruff falling off when shook. The plants will be weak. The result of whitefly damage is yellow leaves that eventually die. Honeydew from whiteflies drops on stalks and encourages fungal growth. As a result, stalks are undersized and poorly colored. Spray with insecticidal soap every two or three days for two weeks. As a last resort, spray with pyrethrum two times, three or four days apart.
These pests are uncommon in rhubarb and unlikely to cause you trouble. Soon you will be having an abundance of rhubarb. Any surplus that you are unable to use now may be frozen or canned for future use. There are several successful methods of freezing. Food preservation of rhubarb via freezing begins by washing the stems and cut in one-inch pieces. Freeze the pieces on baking sheets or shallow pans. After the pieces are frozen, they should be packed into airtight containers or plastic bags. The advantage of this method is that you can remove the exact amount that the recipe calls for. Rhubarb may also be sugar packed by mixing one cup of sugar with four or five cups of rhubarb. Let stand until sugar is dissolved. Pack into containers leaving 1/2-inch headspace. Freeze. Another method is to syrup pack. Place rhubarb into containers. Cover with cold, 40-50 percent syrup. Leave 1/2-inch headspace. To make 40 percent syrup, dissolve 3 cups sugar in 4 cups water. To make 50 percent syrup, use 4 cups sugar to 4 cups water.
Rhubarb can also be canned. Wash and cut into 1/2 to 1-inch pieces. Add 1/2 to 1 cup sugar for each quart. Let stand until juicy — about 3 or 4 hours. Bring to a boil slowly in a covered pan. Pack into clean jars. Adjust lids. Process them (pints or quarts) in boil- ing water bath for 10 minutes. Rhubarb can be used in a variety of ways from refreshing drinks to marmalade to Jell-O to pies.
4 cups diced rhubarb
1 cup granulated sugar
1 box strawberry Jell-O
1 white cake mix (homemade, preferably)
1 cup water
1 stick butter, melted
Preheat oven to 350°F.
Grease 9 x 13 cake pan. Place rhubarb in pan. Sprinkle with sugar and Jell-O. Sprinkle cake mix evenly over top. Pour water and melted butter over cake mix. Bake for approximately 1 hour. Serve with ice cream or whipped cream.
In a 4 qt. pot, fill half full of rhubarb and fill up with water. Bring to a boil. Let stand 1⁄2 hour, drain. This can be canned. To make drink:
1 small can frozen lemonade
1 small can frozen orange juice
2 qts. rhubarb juice
3-1/2 qts. water
1 pkg. raspberry Kool-Aid
2 cups sugar
Mix all together. Add ice cubes.
Rhubarb Refrigerator Dessert
1 cup sugar
3 tablespoons cornstarch 1/2 cup water
4 cups chopped rhubarb
2 cups graham cracker crumbs 1/2 cup butter (or margarine)
1 cup whipped cream
1-1/2 cup miniature marshmallows 1/4 cup sugar
1 pkg. vanilla pudding
Filling: Stir sugar and cornstarch together. Stir in water. Add rhubarb. Boil until thick. Set aside to cool.
Crust: Combine graham cracker crumbs and melted butter. Reserve 1⁄4 cup for garnish on top. Press remainder of crumbs against sides and bottom of 9-inch square baking dish.
Topping: Spread rhubarb mixture over crust. Top with sweetened whipped cream combined with marshmallows. Prepare pudding according to package directions. Spread over top. Sprinkle with reserved graham cracker crumbs and refrigerate.
Originally published in Countryside March / April 2013 and regularly vetted for accuracy.
Growing rhubarb in Western Australia
Rhubarb (Rheum rhaponticum) originates from China and is a member of the Polygonaceae or dock family. The main part of the plant is the crown which is semi-woody and perennial. It is valued for its long, thickened, red stalks — up to 75cm long — which arise from the crown and carry the large leaves. The stalks are used as a dessert — mostly in pies — and have an acidic taste. They contain useful levels of acids (pH 3.0–3.6), sugars, fibre, protein, potassium, calcium, magnesium and vitamin C. The leaves are poisonous and may contain high levels of oxalic acid.
In Western Australia, a small amount is grown commercially throughout the year for the domestic market, mainly in the Wanneroo area. Local production is lower in the cooler months but imports from Queensland supply the market from April to October.
Climate and soils
Rhubarb grows best in cool to warm conditions and yields and quality decrease as the temperature rises above 27°C. The stalks colour best in cool temperatures. It will withstand slight frosts. Heavy frosts may cause dieback but the plants will resume growth with the onset of favourable conditions.
Rhubarb is a deciduous plant in Europe. In Western Australia it retains its leaves throughout the year but is less vigorous in winter.
Rhubarb is adapted to a wide range of soils in the pH range of 5.5 to 6.5 as long as they are well drained and prepared with large amounts of added organic matter such as conditioned poultry manure or compost.
Propagation and planting
Growers normally plant a new area each year. Rhubarb can be propagated by division of crowns into planting pieces or from seed. Crown division is preferred where suitable good quality material of proven varieties is available.
New areas are established, preferably from summer to early winter or from August to September, by planting vigorous, disease-free crowns. Growers have selected plants with desirable characteristics from seedlings, which can be reproduced by division of crowns. These are divided into planting pieces by cutting between the ‘eyes’ so that a piece of the crown has at least one eye. Six to ten cuttings can be made from a crown older than two years.
Named varieties are difficult to obtain in Western Australia and they are expensive. Growers may not supply their own varieties to other growers, and bulking-up of new varieties may be slow.
Variable plant types result from seedling plantings, but this serves a useful purpose in selecting superior types for subsequent multiplication by crown subdivision. This is the main method used by new growers entering the industry as it is cheap and seed is readily available.
Careful selection of superior plant types over a period of years has resulted in the development of local types with marked improvement in yield, quality and uniformity.
Plantings can be established from seed by transplanting seedlings raised either in open seedbeds or in containers, preferably in autumn. Transplants are put out in the field at six to eight weeks from seeding at 30cm apart and assessed for yield and quality. Many of the seedlings will be inferior, with stems which are too green. The best selections should be established and can be bulked up after two to three years by dividing the crowns.
The main plant characteristics selected for are high yield, regular cropping (five to six picks per year), straight, erect, evenly red-coloured stalks of uniform thickness and length, ease of harvesting and adaptability to seasons.
Green-stalked plants are as suitable for cooking as red-stalked varieties but the market perception is that these are unripe and therefore only red-stalked varieties are marketed. Green-stalked varieties are preferred in some countries.
The most popular plant spacings are 90 to 120cm between rows and 60 to 75cm between plants within rows. When dividing crowns, take care not to damage shoots or buds. Plant crowns and seedlings at the correct depth; the buds of the crowns should just be above soil level. Do not plant too wide apart, as this may result in increased plant flowering.
Growing the crop
Rhubarb is a heavy feeder. Apply compost at around 50 cubic metres per hectare before planting and every year after planting. This adds organic matter to the soil, supplies nutrients and helps retain moisture.
Apply a fertiliser to supply 105kg/ha of phosphorus. This rate can be reduced on old vegetable ground or if compost is regularly used. The crop will respond to balanced fertilising of nitrogen and potassium every one to three weeks. Apply these nutrients as 80kg/ha of urea and 75kg/ha of muriate of potash. Do not apply too much nitrogen as this will result in excessive flowering and elongated, poor quality stalks. Apply 50kg/ha magnesium sulphate every three months.
Rhubarb is often affected by manganese deficiency on alkaline soils. This shows as a mottled chlorosis (yellowing) on the young and medium-aged leaves.
Apply the following rates of trace elements to the soil every 18 months:
- 20kg/ha manganese sulphate to supply manganese
- 18kg/ha borax to supply boron
- 18kg/ha ferrous sulphate to supply iron
- 18kg/ha copper sulphate to supply copper
- 18kg/ha zinc sulphate to supply zinc
- 2kg/ha sodium molybdate to supply molybdenum.
Analyse the soil and irrigation water for nutrients before planting, plus one to two analyses of the youngest mature leaves after planting. This will enable you to adjust the fertiliser program and provide information on nutrients that are deficient or toxic. Some of the suggested nutrients may be deleted or reduced if they are sufficiently high in the irrigation water and soil, including sources from compost and fertilisers from previous cropping.
Do not apply excess fertilisers, because nitrogen, phosphorus and potassium are easily washed through sandy soils by rainfall and irrigation. This may lead to groundwater pollution in rivers and estuaries.
Rhubarb requires a higher level of watering than most vegetables.
Plants must be kept well watered, with one watering per day in early morning from April to October — dependent on rainfall — and two waterings per day, half between 7 and 9am and half between 2 and 3pm from November to March.
Table 1 is a guide for watering, but there has been no research on rhubarb to obtain the precise watering needs of the crop. Over-watering after planting crown divisions may cause rotting.
Evaporation data from Medina Research Station, Western Australia represents average conditions and adjustments must be made for marked changes in temperatures, humidities, effective rainfall and wind speeds. Use evaporation data from the nearest meteorological station if your property is not situated near Medina.
Typical butterfly sprinklers are spaced at 277/ha with an output of 15L/minute or 4.15kL/ha/minute. Typical knocker sprinklers are spaced at 69/ha with an output of 22L/minute or 1.52kL/ha/minute. Irrigation time has been adjusted to compensate for the efficiency rating of butterfly (85%) and knocker (80%) sprinklers.
Disease, pest and weed control
The main disease of rhubarb is downy mildew (Peronospora destructor) which appears as brown patches on the leaves, especially after storms from May to October.
Rhubarb can be killed by crown rot caused by Rhizoctonia or Phytophthora diseases. These diseases may be difficult to control. Ensure that rhubarb is rotated every few years with other crops and that plants are grown on soils with good drainage.
Rhubarb may be affected slightly by Alternaria and Phoma species, which cause black spots on the leaves.
Few pests damage rhubarb but keep a look out for aphids, African black beetle, grubs, mites, slugs and snails, vegetable weevil and wingless grasshoppers. Sugar beet nematode (Heterodera schactii) may cause damage. The cysts on the roots look like sugar grains. Root-knot nematode will also damage rhubarb.
Control of weeds in a mature crop is difficult as deep mechanical hoeing may damage the root system. Shallow hand-hoeing may be the best means of weed control.
The registration and availability of chemicals for disease, pest and weed control change regularly. Consult a trained and experienced horticultural agronomist or the Australian Pesticides and Veterinary Medicines Authority (APVMA) website for chemicals which are currently registered or have a permit for use on this crop.
The information on the label or permit for a chemical must be followed, including directions for use, critical use comments, withholding period and maximum residue limit. Quality assurance (QA) schemes for horticultural crop production require producers to have current information on chemical registrations and permits readily available.
Remove flowers as they will cause difficulties with boom spraying against pests and will deplete nutrients required for future stalk production. Flowering is most common after cold winters and hot summers.
Harvesting the crop
Pull the stalks away from the plant with a downward motion so that the entire stalk is removed. Cutting the stems will result in rotting. Growers usually pick the mature stems and leave the four youngest stems. The plant is ready for picking just before the sides of the oldest leaves begin to turn down.
New plantings are ready for picking after nine to twelve months. When established, rhubarb may be picked every six to ten weeks throughout the year.
The best crops are produced between April and July. The stalks show most colour from May to December.
There may be a shortage of rhubarb in late winter and early spring when demand is highest and production is affected by lower temperatures. Prices are usually highest from June to September and lowest from November to March. A good yield is 15t/ha per year.
Packing and storage
The crop is washed, trimmed, graded and packed loose or in 0.5–1.0kg bunches (five to ten stalks), held by rubber bands, in 18 or 48L (10kg) plastic crates or cartons. Discard damaged and split stalks and trim the leaves to within a few centimetres of the main stalk.
Rhubarb can be stored at 0°C and over 90% relative humidity for up to two weeks.
Life of the crop
Rhubarb can be picked for 10 years, but it is preferable for a commercial crop to be kept for three to six years.
The original version of this material was authored by John Burt.
Remember, seeing the damage will make it much easier for the professional to assess what is happening in your garden.
If rhubarb pests have become a problem, when possible, treat your plants using natural and organic insecticides and pesticides, or make a slug trap.
There are also conventional chemical herbicides which can be used for rhubarb. When treating garden plants, always remember to shield your crop from the contact sprays. Check with your local garden center for a recommended product.
GO to Natural / Organic Insecticide Recipes to Make at Home
Rhubarb Pest Identification
My rhubarb plant leaves often develop many very small holes in them.
I believe this is due to aphids (For example, the “Black Bean Aphid”) or other small insects. Large infestations of aphids may cause the rhubarb leaves to curl or wilt.
“Flea Beetles” may cause damage to newly planted rhubarb by their feeding on tender rhubarb leaves.
They become a rhubarb pest during periods of hot, dry weather.
Since the leaves of rhubarb plants are poisonous, and discarded when the rhubarb is harvested, I have not found it necessary to treat the rhubarb leaves for these holes.
Slugs are rhubarb pests that are commonly found on the stalks and occasionally on the leaves.
The slug feeds at night, leaving damaged stalks and occasionally affect the leaves.
Slugs may become a problem where there is poor soil drainage or heavy weed infestation.
After harvesting rhubarb dispose of the leaves immediately, do not leave them to decompose alongside the rhubarb plants. Slugs thrive in wet areas and around decaying matter.
If the edges of the rhubarb leaves are being eaten away (jagged edges) or there are large holes in the leaves, or the stalks have scars, the problem may be slugs (see image below).
Slugs can Cause Holes to Appear on the Rhubarb Leaves
Slug and Snail “bait” can be purchased in the form of small “pellets” that poison the slugs.
A more natural approach to controlling these rhubarb pests, is to make your own “slug trap”.
Making your own slug trap is a natural and inexpensive way to rid your rhubarb garden, (or any garden), of slugs (and snails).
GO to How to Get Rid of Slugs – Make a Slug Trap
Slug bait can be purchased online at *Amazon.com.
Click on the images below for more detailed product information, and customer product reviews.
Rhubarb Curculio Beetle
The “Rhubarb Curculio”, (Lixus concavus), a yellowish member of the weevils, or “snout beetles” group is a pest which prefers rhubarb.
These beetles are about 1/2″ – 3/4″ long. They typically bore their way into the stalks and crowns.
Damage by these beetles is usually visible on the stalks (sometimes the leaves), with circular feeding and/or egg laying sites.
The adult Rhubarb curculio overwinters in leaf litter or other similar sites and appears in mid-May. The adult makes feeding and egg punctures in the crowns, roots and stalks; a jelly-like sap substance exudes from the wounds, often with extraneous material trapped within (see image below).
Rhubarb Plant Damage by the Curculio Beetle
The best way to help avoid the Rhubarb Curculio from damaging your rhubarb is to ensure that there is no Dock Weed Plants in the area around your rhubarb garden.
Dock Weeds are perennial weeds and a member of the Buckwheat Family of plants that grow 0.8 to 1.5 metres tall. They have a deep penetrating yellow taproot, and dark green leaves that are wavy and crisp along the margins. Dock Weeds turn a rusty-reddish colour when mature.
Thistle and Sunflowers may also harbour these beetles.
If your rhubarb plants have become infested with these snout beetles, use an insecticide or remove infected stalks and burn them to be sure to rid the area of these rhubarb pests.
Potato Stem Borer
The “Potato Stem Borer” may become a rhubarb pest in midsummer.
These caterpillars are about 3 1/2″ long, and pinkish-white in colour.
They bore into the rhubarb stalks. The adult moth lays their eggs on the stems of grasses in August, which in turn hatch the following spring.
The best way to help avoid the Potato Stem Borer from damaging your rhubarb is to control the couch grass and other weeds in and around your rhubarb garden. If the weeds are controlled, the area becomes less attractive for egg laying by the adult moth.
Tarnished Plant Bug
The “Tarnished Plant Bug” is usually a pest of new rhubarb plantings.
The adult Tarnished Plant Bug is a light brown-reddish brown colour and about 5 mm in length.
They occur throughout the rhubarb growing season and can damage rhubarb by feeding on young leaves.
To help control the Tarnished Plant Bug, try to keep the areas directly adjacent to the garden free of weeds. Also, avoid planting rhubarb beside legumes.
In some instances, in the spring, hungry wildlife may up-root rhubarb and eat the crowns, as stored starches are turned to sugars for new rhubarb leaf growth.
I cannot think of an easier vegetable to grow in your garden than the rhubarb plant.
Over all the years I have grown rhubarb, I have seldom experienced rhubarb plant pests to the extent that I needed to take any special corrective measures. 🙂
Here below, are links to helpful information about growing rhubarb in the home garden (or use the navigation bars).
Rhubarb PLANT CARE
Rhubarb COMPANION Gardening
More COMPANION Plant Ideas
LINKS RELATED TO RHUBARB GARDENING
ORGANIC PESTICIDE RECIPES and Information
EASIEST Vegetable to GROW
WEED CONTROL Tips
WHERE to Grow Rhubarb
How to GET RID OF SLUGS
CONTAINER GARDENING – Can Rhubarb be Grown in Containers/Pots?
Yorkshire FORCED RHUBARB
TOP of Rhubarb Pests
HOME to Rhubarb Information Homepage
You might enjoy using rhubarb in pies and other foods. Most of us never think about trying to make insecticide from rhubarb leaves. I know I didn’t.
We know the Rhubarb stalks and stems are perfectly edible, on the other hand the leaves are not.
How To Make Insecticide From Rhubarb Leaves
If you grow a garden, you can use the leaves of the rhubarb plant to act as a natural insecticide. Here’s a short guide that will help you create this helpful concoction.
Why Do Rhubarb Leaves Work To Repel Insects and Pests?
Rhubarb leaves contain oxalic acid which can not only stop your heart but makes a great natural pesticide for leaf eating insects.
If plant lice (aphids) or other insect pests attack your plants, the acid in the rhubarb leaves should work to suffocate and otherwise disturb them. Over time you won’t need to worry about the bugs.
How To Make Pesticide From Rhubarb Leaves
The first thing you must do to make an insecticide solution: collect rhubarb leaves. Of course, if you grow the plant yourself, you can use your own leaves. If not, you can head down to the supermarket and buy some rhubarb, which typically still has the green leafs attached.
Rhubarb Leaf Insecticide Recipe
Cut the stems off the leaves to use in cooking or other activities, and keep the leaves for your insecticide.
Once you’ve your rhubarb leaves, you’ll need to boil them in water. Try to keep a 1:3 ratio between the leaves and water.
For instance, if you’ve got a cup of rhubarb leaves, use three cups of water. Boil the leaves in a pot for about half an hour, and allow to cool.
Next, using a strainer, remove all the leaves from the pot. Add a little liquid dish detergent, and then pour the solution into a spray bottle. That’s all there is to it!
Once you’ve made the natural insecticide spray, begin spraying the various plants in your yard or garden. You might want to do this spraying in mid-morning or mid-afternoon so that it doesn’t evaporate too quickly. Over time, you should start to see that insects find your plants less attractive.
NOTE: Always TEST the spray in a small area to make sure the plant will not suffer any damage.
How Long Can You Keep The Insecticide Spray?
Ideally, you’ll want to use the entire rhubarb pests control solution within a day or two. Keep in mind that the longer you wait, the less effective it may become.
Should You Use The Spray On Plants Grown For Food?
While insecticide made from rhubarb leaves uses can be effective against insects on all different kinds of plants, you may want to exercise some caution and avoid spraying the solution on plants you plan to eat.
The oxalic acid content in the spray may be too high and could make you or a family member ill.
Now that you’ve got more information about how you can make and use a natural insecticide from rhubarb leaves, cook up a batch. You should soon see less bugs and more beautiful plants.
Rhubarb Plants Turning Yellow
Why are my rhubarb plants turning yellow and soft? I have 3 plants, two have done this.
Hardiness Zone: 9a
Jim from Santa Ynez, CA
Getting rhubarb to grow successfully in your zone may be a tall order. Rhubarb does best where it gets cold. In fact, it will be the most productive if it experiences occasional winter temperatures below 40 degrees F.
One possibility is that your rhubarb is simply getting to much heat. You might want to consider erecting a cheap screen to give it some afternoon shade. A roll-up blind will work well for this because it will still provide your rhubarb with some filtered sunlight, while cutting down on the heat.
Water is another problem in warmer zones. Due to their broad leaves, rhubarb needs a lot of it, especially in warmer zones. I would recommend watering at least every other day as well as giving it an occasional boost with a liquid fertilizer.
Rhubarb needs soil with good drainage, especially when grown in areas that experience high levels of humidity. Yellowing and wilting leaves could simply be a lack of water at crucial times. Then again, the soft stalks may also point to a fungal disease. Check the base of the crown for white fungal growth or rot spots. Affected plants should be completely removed, disposed of in the garbage, and replaced with new plants.
some of my rhubarb leaves are turning yellow, should I pick the larger leaves, and leave the smaller ones alone?
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