Rhubarb leaves in compost

4 things to do with rhubarb, other than eating it

Everyone knows that rhubarb is a delicious addition to a variety of dishes, from the classic rhubarb pie to crumbles, cookies, breads, muffins and more.

But there’s so much more to this pink veggie (yep not a fruit). When you’ve had your fill of rhubarb desserts, here’s five other things to try…

Clean your pots and pans

Back in the day, rhubarb was the solution to burnt pots and pans. Research by Marigold found that the trick is just as good as it was in the 40s. It’s easy to do. Just chop up some rhubarb into small pieces, and boil it in the afflicted pan until you get a glue-like consistency. It should take about 10 minutes. Once you have it, rinse with water and voila!

Make a natural insecticide

You can use your plant to protect your other plants. Rhubarb leaves contain oxalic acid, a poisonous compound, which you can use to defend against leaf-eating bugs. The oxalic acid is the reason you chop off the leaves before baking rhubarb, and it’s also why you shouldn’t use this natural insecticide on plants you intend to eat. You should also keep it away from children and dogs.

To make it, boil rhubarb leaves in a pot and leave to simmer for 30 minutes. Remove the leaves, and drain the contents into a spray bottle along with a teaspoon of detergent. Label clearly and wash everything you used.

Feel better

Rhubarb has been a standard ingredient in traditional Chinese medicine for hundreds, if not thousands of years. According to The Rhubarb Compendium, rhubarb roots are best known as a tool for settling the digestive system, but can also be used to relieve constipation, reduce swelling and soothe burns and cold sores. The medicinal strain of rhubarb is different from the one we usually eat, so get this natural cure from a health store, instead of the garden.

Lighten your hair

For the DIY stylists, rhubarb can also be used to lighten blonde or brown hair. The medicinal variety is strongest, but this trick works even with the roots of the garden-variety plant. Almanac.com suggests putting “half a cup of fresh, chopped root in a quart of water for 20 minutes in a covered stainless-steel pot”. Leave it overnight, then strain in the morning. Test it first on a strand, and if you like it, wash your hair, then pour the dye through your hair. Repeat for greater strength and air dry, don’t rinse.

Rhubarb is incredibly versatile. It’s most commonly used in baking, but the following recipes show that it’s great for savory dishes, as well as drinks and preserves.

It was late fall when my family moved into a new house last year, so I wasn’t aware of the magnificent rhubarb patch tucked into a corner between the shed and cedar hedge. In early springtime, my children excavated the sandy corner with their Tonka trucks, but one day I spotted tiny curled rhubarb leaves poking out of the mangled dirt and evicted my children from that particular dirt patch. (They moved to the herb garden instead, where they began decimating the peppermint.) Then we watched the amazingly resilient rhubarb recover and thrive.

Now I harvest handfuls of the deep red stalks every few days. I love it for baking, preserving, and cooking, while my kids sport the giant leaves as sun hats until they go limp. (Just don’t eat the leaves! They contain oxalic acid, a toxin that should not be ingested in large amounts.)

While the rhubarb season may be ending in the United States, it’s in full swing here in Ontario where I live. Use this unusual perennial and try some of these delicious recipes.

1. Rhubarb and Ginger Jam

For once, rhubarb is not paired with strawberries in a jam recipe! The combination is common but frustrating when strawberries are not yet in season and there’s a ton of rhubarb waiting to be used. So I was delighted to discover this recipe that fills out the rhubarb with a double punch of ginger – both candied and fresh. (I substituted 2 teaspoons ground ginger for the fresh while boiling the fruit down, since I forgot to add it earlier. The result was still delicious.) I have now made two batches and declare it my newest favorite jam recipe.

Find recipe here.

2. Rhubarb Buckle with Ginger Crumb

The combination of rhubarb and ginger is delicious. This is one of the best cakes I’ve ever made – moist and soft with rhubarb mixed right into the batter, with a crispy, sugary crumble topping that was hard to resist straight from the bowl.

Find recipe here.

3. Rhubarb Lentil Soup

Who says rhubarb has to be sweet? It closely resembles celery, after all, which nobody would ever think of using in a dessert! This traditional Middle Eastern lentil soup recipe uses a hefty quantity of fresh rhubarb to add a bright, sour taste.

Find recipe here.

4. Rhubarb Compote

Compote is a fancy name for stewed rhubarb, which is a very useful recipe to know how to make. Compote can be eaten plain, mixed into yogurt and granola for a tasty breakfast, served over ice cream or vanilla pudding. I like to add a touch of almond extract.

Combine 4 ½ cups chopped rhubarb, 1 ½ cups granulated sugar, and 2 tbsp lemon juice in a pan. Stir until sugar dissolves. Simmer until rhubarb softens, about 7 minutes. Transfer to a bowl and chill.

5. Rhubarb and Raspberry Crostata

Wow your dinner guests with this impressive yet straightforward dessert. It’s much easier than making a pie but just as good. The whole-wheat crust is fragile yet easy to repair. It goes perfectly with the tart rhubarb-raspberry combination, but feel free to substitute based on what fruits are in season.

Find recipe here.

6. Rhubarb Iced Tea

This is my mother’s recipe. It’s a refreshing, delicious drink for hot days, served over ice, perhaps with a bit of ginger ale to add fizz.

Combine 6 cups chopped rhubarb and 1 cup granulated sugar in a saucepan. Add 2 cups of water. Stew over medium heat until soft, 7-10 minutes. Strain if you prefer it clear (although Mom recommends leaving some pieces of rhubarb).

Meanwhile, make green tea. Steep 4 tea bags in 2 liters (half-gallon) of water. Remove tea bags once flavor is intense. Add rhubarb mixture. Add sugar to taste and stir to dissolve. Chill and serve cold.

7. Cinnamon-Rhubarb Muffins

Whitney/CC BY 2.0

I come from a family of rhubarb lovers, as you may have guessed by now. My sister makes these Cinnamon-Rhubarb Muffins and sells them freshly baked at her restaurant. She bakes them a wood-fired pizza oven early in the morning when the oven is still cool. They get snatched up almost as quickly as they’re made.

Find recipe here.

natalia bulatova/

Like most people in the Midwest, I really look forward to spring. After all, there’s a lot to love: warm temperatures, blooming plants, and—my personal favorite—spring produce.

One of the most iconic spring fruits (well, technically it’s a vegetable, but we use it as a fruit) is rhubarb. The pretty pink stalks are a delicious addition to pies, muffins, jams, and more. (These rhubarb recipes are ready for spring!)

However, rhubarb has a little bit of a shady side. I was always warned to stay away from rhubarb leaves because they’re poisonous. But is the rumor true? Here’s what we found.

Is rhubarb poisonous?

Yes and no. The stalks are totally safe to eat. You can even enjoy them raw—but be warned, they’re very tart!

The leaves are a different story. They contain a chemical called oxalic acid which, when consumed in large quantities, can be fatal. According to National Geographic, oxalic acid binds to calcium ions in your blood and makes them ineffective. This process can lead to kidney problems or even death. Now that you know about some of the potential dangers, here are some surprising foods that could give you food poisoning.

The verdict

As scary as this process sounds, don’t panic. You would have to eat several pounds of rhubarb leaves to reach a toxic level—so don’t feel like you need to toss the whole batch if tiny leaf scraps end up in your rhubarb muffins. But do avoid eating the leaves whole—even a few can make you feel sick.

And, if you grow rhubarb in the garden, keep Fido away from the patch. Most pets are a lot smaller than humans, so it takes very few rhubarb leaves to do damage. Give your pup one of these dog-friendly foods instead. Want to learn more about foods that could be toxic? Find out about the most dangerous foods on the planet.

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Hit or myth?

Never put poisonous plants into your composter!

When I was growing up, our rhubarb patch was just a stone’s throw from our house, behind a long row of Nanking cherries. The rhubarb leaves were always huge and the stalks were very thick and juicy thanks to the rich, deep soil and plentiful irrigation.

When Mom harvested the rhubarb to make her delicious pies and strawberry-rhubarb jam, she would simply give each stalk a quick twist – breaking it free from the root crown – and then lop the leaves off with a quick flick of her kitchen knife. The leaves were then tossed between the rows of corn or whatever vegetables happened to be growing near the rhubarb patch that year. Mom never gave a second thought to the possibility that the poisons from the rhubarb leaves might eventually find their way into the fruits and vegetables growing nearby.

Now, I don’t recall that my stomach was even a tiny bit queasy from eating fruits and vegetables grown in the same spot where Mom threw her rhubarb leaves. But the question of whether or not it is wise to incorporate poisonous plant material into soils where edible plants are grown is a concern for many gardeners.

A bit of science The primary reason that plants like rhubarb produce toxic substances is because they are lousy runners. Since they can’t pull up their roots and run away from hungry critters, they have little choice but to stand and fight. Some plants rely on structures like thorns, spines or hairs that discourage some animals and insects from eating them, while others brew chemicals that are either unpalatable to herbivores (humans included) or downright poisonous.

Rhubarb is an example of a plant that has taken the chemical route. It synthesizes oxalic acid and a few other toxins in its leaves that stave off attack by many pests. Many other common garden plants like monkshood, foxglove and angel’s trumpet create their own special blends of toxins, reducing or eliminating feeding by a wide range of organisms.

But the adage one man’s poison is another man’s meat applies to even the most deadly toxins in plants. Once poisonous plants meet garden soil or are blended into a compost bin, they are under relentless attack by a wide variety of soil micro-organisms that treat the poisons as just another food source. Sunlight, oxygen, heat or cold, and even water can also play a role in detoxifying chemicals.

The other big problem with plant toxins is that they are often, well, big. Basically, trying to fit a comparatively large toxin through the small root-hair pores just doesn’t work very well.

What should you do? Don’t be overly concerned about plant toxins in your soil finding their way into your salad. Let Mother Nature break down poisonous plants into valuable organic material rather than sending these plants to a landfill. However, it is prudent to be a bit cautious when handling plants like stinging nettle or monkshood that contain skin irritants. The toxins in these plants will be broken down in the composter, but the journey to the composter can be a bit perilous. Gloves and long-sleeved clothing are essential tools!

Now, if you are still a little concerned about eating, say, a tomato that has been growing in compost that was comprised of some poisonous plants, think of it this way – many people apply cow manure to their tomato patch but don’t ever worry about the fruit having a distinctly manure flavour.

Now the thought of that does make me feel a bit queasy.

Just Ask Us: Can rhubarb become dangerous if exposed to cold weather?

Q: Can rhubarb become dangerous if exposed to cold weather?

A: Rhubarb plants as a whole aren’t permanently damaged by cold freezes in the spring, but the edible stalks can be altered by freezing weather in a way that is poisonous to humans, UW-Extension horticulturist Lisa Johnson said.

Rhubarb leaves contain oxalic acid, which is toxic to humans, but that acid is generally not found in the stalks, which is why those are safe to eat. Cold temperatures can change that distribution of oxalic acid, Johnson said.

“Once temperatures fall to a range of the lower to middle 20s, oxalic acid in the leaves will (move) to the rhubarb stalks that we harvest,” Johnson said. “When consumed, oxalic acid can crystallize in the kidneys and cause permanent damage to the organs.”

The rhubarb will show signs of damage when exposed to freezing temperatures, which can warn gardeners harvesting it, Johnson said. The leaves will wilt and blacken along the edges where damaged, and the stalks will be limp with “poor texture and flavor,” Johnson said.

Damaged leaves and stalks should be removed from the plant and discarded.

“It’s safe to harvest rhubarb if the plants show no signs of damage two or three days after the freeze event,” Johnson said.

Any stalks that emerge after the freeze are safe to harvest, Johnson said.

Should you eat any damaged stalks or some of the leaves, you don’t need to rush to an emergency room. National Geographic reports that a person would need to eat several pounds of rhubarb leaves to reach toxic doses.

— Shelley K. Mesch

Other uses for Rhubarb

Rhubarb has many uses. The most common is medicinal. Rhubarb has been used in medicines and folk healing for centuries.

Cleaning pots and pans

Use Rhubarb to clean your pots and pans (no joke!) If your pots and pans are burnt, fear not! An application of rhubarb over the afflicted area will bring back the shine in next to no time. Environmentally friendly too!

Hair Color

This is a fairly strong dye that can create a more golden hair color for persons whose hair is blond or light brown. Simmer 3 tbsp. of rhubarb root in 2 cups of water for 15 minutes, set aside overnight, and strain. Test on a few strands to determine the effect, then pour through the hair for a rinse.

Insecticide

Rhubarb leaves can be used to make an effective organic insecticide for any of the leaf eating insects (cabbage caterpillars, aphids, peach and cherry slug etc).

Recipe 1

  • Basically you boil up a few pounds of rhubarb leaves in a few pints of water for about 15 or 20 minutes,
  • allow to cool,
  • then strain the liquid into a suitable container.
  • Dissolve some soap flakes in this liquid and use it to spray against aphids.

So, next time you pick some rhubarb stems to eat, you can put the leaves to good use rather than just composting them (which isn’t in itself such a bad use, I guess).

Recipe 2

  • Shred 1.5 kg (3 lbs.) rhubarb leaves
  • and boil in 3.5 liters (1 gallon) of water for 30 minutes.
  • Allow to cool and then strain. (use old utensils if you can – the rhubarb will stain most things and poison the rest.
  • In a small saucepan heat to boiling point 2.5 litters (2.5 quarts) of water and mix in 125 g (4 oz) of softened soap ends (any bits of soap left in the shower).
  • Allow to cool (stirring regularly to make sure all the soap is dissolved).
  • Add to the strained leaf mixture, stir vigorously, and the spray directly onto infested leaves.

The unused spray can be kept for a day or two, but keep your kids away its still quite harmful.

Rhubarb inspired art

Paintings

James Grainger, is a British artist who specializes in oil paintings of Vicars and Morris Dancers in curious and surreal situations. Many of his paintings include rhubarb, as can be seen in the sample to the right. Be sure to visit his web page: James Grainger’s Gallery

Music

The Rhubarb Tart Song

1. I want another slice of rhubarb tart.
I want another lovely slice.
I’m not disparaging the blueberry pie
But rhubarb tart is oh so very nice.
A rhubarb what? A rhubarb tart!
A whatbarb tart? A rhubarb tart!
I want another slice of rhubarb tart!
2. The principles of modern philosophy
Were postulated by Descartes.
Discarding everything he wasn’t certain of
He said ‘I think therefore I am a rhubarb tart.’
A rhubarb what? A rhubarb tart!
A Rene who? Rene Descartes!
Poor nut he thought he was a rhubarb tart!
3. Read all the existentialist philosophers,
Like Schopenhauer and Jean-Paul Sartre.
Even Martin Heidegger agrees on one thing:
Eternal happiness is rhubarb tart.
A rhubarb what? A rhubarb tart!
A Jean-Paul who? A Jean-Paul Sartre!
Eternal happiness is rhubarb tart.
4. A rhubarb tart has fascinated all the poets.
Especially the immortal bard.
He caused Richard the Third to call on Bosworth Field:
‘My kingdom for a slice of rhubarb tart!’
A rhubarb what? A rhubarb bard!
Immortal what? Immortal tart!
As rhymes go that is really pretty bard!

John Cleese

Poetry

Rhubarb Limericks

Subject: Inconsequential Rhubarb Nonsense
From: “PeterW” <PeterWlims demon uk>
Date: 1998/10/08
Newsgroups: alt.jokes.limericks

Rhubarb when raw is so tough
And its leaves contain poisonous stuff,
But when cleaned and de-soiled
Dipped in sugar and boiled
Then the stalks are quite tasty enough.

Subject: Re: Inconsequential Rhubarb Nonsense
From: “Marlene” <mlewismissionx com>
Date: 1998/10/12
Newsgroups: alt.jokes.limericks

Rhubarb is much better in pies
Sweet, sour and attracting flies
It’s good as gooseberry
And tasty as cherry
Please, have a slice — do not be shy!

Subject: Re: Inconsequential Rhubarb Nonsense
From: SCSaintpacbell net
Date: 1998/10/12
Newsgroups: alt.jokes.limericks

We would just wipe it off and chew
Then watch each other’s mouth go askew
So sour yet so good
That was in my boyhood
Things were tastier circa 1942.

Subject: Re: Inconsequential Rhubarb Nonsense
From: tuttagioiaaol com (TuttaGioia)
Date: 1998/10/09
Newsgroups: alt.jokes.limericks

“Your rhubarb, I’ve noticed it grows
By the outhouse where everyone goes!”
Grandad said, “Lad,
It isn’t so bad…
They’re family! Just people we knows!”

CFC control

The January 19 issue of SCIENCE Magazine reported that scientists have discovered a way to convert environmentally damaging chlorofluorocarbons (CFCs) such as Freon into four harmless components: sodium chloride (table salt), sodium fluoride (an ingredient used in toothpaste), carbon, and carbon dioxide. CFCs have been historically hard to destroy, because they are relatively inert. Professor Robert Crabtree and graduate student Juan Burdeniuc used sodium oxalate that is found in rhubarb leaves to destroy CFCs. (The article didn’t mention if the researches actually got the sodium oxalate from rhubarb leaves or not but did mention that is where it is found).

Rhubarb Paper

Apparently the fiber in rhubarb is a nice additive to handmade papers. I have found several craft-folk selling or mentioning rhubarb-paper. Here is a sample from “BETH BAKER: Handmade Papers and Journals”.

Footnotes

  1. rhubarb vs. aphids, http://www.lysator.liu.se/ftp/pub/gardening/Edibles/rhubarb_vs_aphids,
  2. Wisdom from Dr. Elizabeth Rutherford of the Cognitive Laboratory, Psychology Department, http://babelfish.psy.uwa.edu.au/brent/fos/eliza/rhub.html, University of Western Australia, Perth, Australia
  3. The Rhubarb Tart song, From the Illinois State University’s College of Fine Arts World Wide Web (WWW) Server, Sponsored by The Office of Research in Arts Technology (ORAT), The College of Fine Arts at Illinois State, and Illinois State University, “Its a Monty Python Collection”
  4. http://tyndale.apana.org.au/~paddo/rhubarb.html, from The wisdom of Tony Savage
  5. Rhubarb Root Golden Hair Coloring, http://www.howtodirectory.com, From The How-To Directory, is a growing database of how-to information; the collected knowledge of generations gathered from individuals and companies who are willing to share their memories and experiences with others.
  6. Rhubarb plus Freon yields toothpaste and salt by Chris Nelder, from http://www.betterworld.com/BWZ/9602/explore1.htm
  7. http://www.howtodirectory.com/folklore/rhubarb.html, The How-To Directory is a growing database of how-to information; the collected knowledge of generations gathered from individuals and companies who are willing to share their memories and experiences with others.
  8. http://art-a-whirl.org/aawbldgs/wndmcf.htm, The Windom Park Cafe and Gallery 1998.

Are Rhubarb Leaves Poisonous?

Make a Natural Insecticide with the Leaves

Rhubarb leaves are considered poisonous due to the fact that they contain high levels of Oxalic Acid. Oxalic Acid is sometimes called “ethane diacid”.

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The edible portion of rhubarb, the stalks, contain only a very low concentrate of oxalates, and are very safe to eat.

Oxalic acid is also found in safe amounts in cabbage, spinach, potatoes and peas, amongst others.

The fact that the leaves are considered to contain oxalic acid is NOT a reason not to enjoy eating rhubarb. The stalks are what is harvested to eat, not the leaves!

Scroll down for a recipe to make a homemade natural insecticide using your rhubarb leaves, and a link to many more recipes for natural and organic pesticides and insecticides.

Leaves of the Rhubarb Plant

Oxalic acid is a poisonous, colorless substance commonly used in products such as metal polishes, stain removers, bleaches, and anti-rust products.

Some of the symptoms of Oxalic Acid poisoning include, abdominal pain, collapse, convulsions, kidney problems, low blood pressure, mouth pain, shock, throat pain, tremors, vomiting, weak pulse. (Information Source: Medline Plus).

Use precautions when harvesting rhubarb by trimming the leaves from the stalks immediately, not using stalks from plants that have been “frost bitten”, and washing the stalks before using them, and before preparing them for the freezer or for canning rhubarb.

Children should be taught to eat only the rhubarb stalks, (if they do not find the raw rhubarb too tart!), with adult supervision.

See Also: Rhubarb Allergy Information

The leaves of rhubarb should never be fed to animals. Some animals such as goats and pigs, have also been poisoned by ingesting these leaves.

Many visitors ask, ” Can rhubarb leaves be composted? “

It would stand to reason that if the leaves are poisonous, then adding them to compost would be a concern.

However, since the oxalic acid is broken down, diluted and pH balanced quite quickly, this is not a concern.

Since humans and animals do not normally ingest matter from a compost, rhubarb leaves should be able to be added safely to the compost.

Go here for more information and tips for composting rhubarb leaves.

Interestingly, the leaves of rhubarb can be used to make a natural insecticide.

If you have a large rhubarb patch, you may be interested in making this natural insecticide using the leaves after picking your rhubarb.

A Recipe for Natural Insecticide Using Rhubarb Leaves

Boil 500 grams of rhubarb leaves in a few pints of water for about 20 minutes.

Allow leaf mixture to cool.

Strain the liquid into a CHILD PROOF/SAFE suitable container.

Add a tiny bit of dish detergent or soap flakes, (not laundry detergent).

Using a spray bottle, spray on leaves to kill off bugs such as aphids and spider mites, June bugs, and fungus diseases.

*NOTE – DO NOT spray this product on ANYTHING edible. Rhubarb leaves contain high amounts of oxalic acid, and are poisonous, and could cause death.

If you are interested in more recipes to make simple homemade Natural Pesticides and Insecticides, Go here

Here are additional pages within this website that provide helpful information about growing rhubarb in the home garden (or use the website’s navigation bars):

GROWING Rhubarb

FORCING Rhubarb

Rhubarb PLANT CARE

Rhubarb VARIETIES

ORNAMENTAL Rhubarb

PLANTING Rhubarb

TRANSPLANTING Rhubarb

Rhubarb COMPANION Gardening

More COMPANION Plant Ideas

HARVESTING Rhubarb

Rhubarb SEEDS

Rhubarb FLOWERS

Rhubarb PESTS

Rhubarb DISEASES

ORGANIC Rhubarb

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 Leaves
HOME to Homepage of Rhubarb-Central.com

Click to enlarge

Field-grown rhubarb will shortly be coming into season and appearing in supermarkets in the UK, so it seems like a good time to take a look at the chemistry behind this odd-looking vegetable. It’s mostly used in pies and desserts, but it’s only the stalks of the plant that we eat – and there’s a reason for that. This graphic takes a look at why, and also looks at the chemical compounds that contribute to the colour and the laxative effect of rhubarb.

Firstly, let’s consider the poisonous nature of rhubarb leaves. It’s generally thought that this is due to the presence of a chemical compound called oxalic acid. This compound doesn’t just occur in rhubarb – it also occurs in lower amounts in spinach, broccoli, cauliflower, and brussels sprouts. Obviously, we eat those pretty regularly just fine; in vindication of the old adage ‘the dose makes the poison’, it’s the higher concentration in rhubarb leaves that poses the problem.

Rhubarb leaves have a comparatively high oxalic acid content of around 0.5 grams per 100 grams of leaves. This is present in the form of oxalic acid, and also in the form of calcium and potassium oxalate salts, and is at a level much higher than that found in other portions of the plant such as the stem. The suggested lethal dose of oxalic acid is in the region of 15-30 grams, meaning you’d have to eat a fair few kilograms of the leaves to reach this dose, but lower doses can still cause nausea and vomiting.

This was discovered to the detriment of the British government in World War I, when, due to food shortages, they advocated eating rhubarb leaves. Of course, this led to cases of poisoning, and at least one death is reported in the literature. The only other study on a death due to oxalic acid poisoning was back in 1960, so the specifics of the mechanism of the poisoning are a little hazy. However, it’s known that, in the body, oxalic acid binds to calcium ions, producing calcium oxalate. Calcium oxalate is insoluble, and as such accrues in the kidneys as kidney stones.

It’s not quite as clear as oxalic acid or oxalates being the culprit, though. Some critics have pointed out that no traces of oxalates were found in post-mortem examinations of those who supposedly died from poisoning after eating rhubarb leaves, and it’s also been suggested that there may be another, as yet unidentified chemical component in the leaves of rhubarb which contributes to their toxicity. Compounds known as anthraquinone glycosides have been suggested as potential candidates, but as yet no specific compound has been identified.

This leads nicely on to a discussion of some of the other compounds found in rhubarb stems, which include anthraquinones. They’re contributors to the colour of rhubarb, although not major contributors – that part is played by compounds called anthocyanins, common causes of colour in plants. The major anthocyanin in rhubarb is cyanidin-3-glucoside. A range of anthraquinones are also present, including emodin (orange), chrysophanol (yellow), physcion (red-orange), and rhein (red). Besides their colour contribution, these compounds and their derivatives also give rhubarb a laxative effect.

The compounds of interest as far as these effects go are the sennosides, derivatives of anthraquinones. During digestion, these compounds are hydrolysed into a number of smaller molecules, including rheinanthrone. It’s rheinanthrone that is thought to be the primary compound behind rhubarb’s laxative effect. Sennosides are also found in the senna plant (hence the name), and are commonly used in laxative medications. They’re included in the World Health Organisation’s list of the essential medicines.

Compounds from rhubarb have also been examined for other potential medical uses. In particular, the anthroquinones have been researched as potential anticancer compounds, with both emodin and aloe-emodin having been shown to exhibit anti-tumour properties.

After more food & drink chemistry? Check out the Compound Interest book, coming in October 2015.

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References & Further Reading

  • Rhubarb – Picture It Chemistry
  • Toxicants occurring naturally in foods (OA) – National Academy of Sciences
  • Anticancer properties of anthraquinones (£) – Q Huang & others
  • Chemistry & pharmacology of rhubarb – a review (OA) – S K Agarwal & others
  • Analysis of the purgative components of rhubarb (OA) – O Haruji & others

Can You Compost Rhubarb Leaves – How To Compost Rhubarb Leaves

Love your rhubarb? Then you probably grow your own. If so, then you probably know that while the stalks are edible, the leaves are poisonous. So what happens if you put rhubarb leaves in compost piles? Is composting rhubarb leaves okay? Read on to find out if you can compost rhubarb leaves and if so, how to compost rhubarb leaves.

Can You Compost Rhubarb Leaves?

Rhubarb resides in the genus Rheum, in the family Polygonaceae and is an herbaceous perennial plant that grows from short, thick rhizomes. It is easily identified by its large, triangular leaves and long, fleshy petioles or stalks that are green at first, gradually turning a striking red in color.

Rhubarb is actually a vegetable that is primarily grown and used as a fruit in pies, sauces and other desserts. Also referred to as the “Pie Plant,” rhubarb contains vitamin A, potassium and calcium – as much calcium as a glass of milk! It is also low in calories and fat, and is cholesterol free and high in fiber.

Nutritious it may be, but the leaves of the plant contain oxalic acid and are toxic. So is it okay to add rhubarb leaves into compost piles?

Garden Myths – Learn the truth about gardening

Rhubarb is a great vegetable that is one of the easiest things to grow. I deadhead the flower stem, mulch with wood chips and that is the only care the plant has gotten in 10 years. It produces every year. But gardeners need to make things more complicated and numerous rhubarb myths have developed.

Forced rhubarb is especially sweet – is this a rhubarb myth?

Rhubarb Myth – Oxalic Acid is Deadly

It is well known that you should not eat rhubarb leaves because of the high levels of oxalic acid. Really? Did you know carrots and radishes contain just as much oxalic acid, and spinach has twice as much? I discussed this rhubarb myth in Will Oxalic Acid in Rhubarb Leaves Harm You.

Don’t Eat Frozen Rhubarb

When the rhubarb plant in the garden gets a touch of frost it goes limp. Some people believe that the frost causes the plant to move oxalic acid from the leaves to the stalks, which now contain toxic levels of oxalic acid.

I did not find any evidence that oxalic acid is moved from one part of the plant to another as a result of frost. And since the oxalic acid levels in the leaves are not toxic (see the above myth) this is really not a concern.

Light touches of frost will not harm the plant and the stalks can be harvested. Heavy frost will turn the leaves and stalks into mush and you won’t want to eat them. These should be pulled and composted. New growth is fine to eat.

Rhubarb Stalks Become Toxic in Summer

Rhubarb stalks are best if harvested in spring and early summer, but they do not become toxic or poisonous in late summer. They can be eaten all summer long.

There are two good reasons not to eat them in summer.

  1. They tend to get woody in late summer and don’t taste as good.
  2. If you harvest too many stalks in spring, the plant needs some leaves to grow food for next years crop. Continual harvesting will eventually kill the plant.

Rhubarb Leaves Should Not Be Composted

This myth is related to the idea that too much oxalic acid can be toxic and who wants toxic compost. Oxalic acid is not easily absorbed by other plants so even if it is in compost, it will not harm other plants or be transferred into food you might eat.

Oxalic acid will also be broken down during the composting process. Once added to soil, it continues to decompose and will not build up in the soil.

Compost those leaves or lay them right on the ground as a great mulch.

Green Stalks Should Not Be Eaten

There is nothing wrong with green stalks – they are fine to eat. Stalk color is affected by both environmental conditions and genetics with genetics playing the major role.

Red Stems are Sweeter than Green Ones

From The Rhubarb Compendium; “A deep red petiole is the more popular among consumers, but these plants are often accompanied by poor growth and yield. Green varieties are often much more productive. Consumers also often assume the red stemmed rhubarb is sweeter than other colors but color and sweetness are not necessarily related. The Victoria variety, which is probably the greenest variety, can produce some very sweet stems.”

Forced rhubarb is sweeter than regular rhubarb. Forcing is a process whereby the plant is covered in spring so that new growth takes place without light. The picture above shows a container placed over part of the plant to produce some forced stalks.

Rhubarb Leaf Pesticide

The use of a natural pesticide made from rhubarb leaves is frequently promoted. Boil the leaves in some water for 20 minutes, cool, add a few drops of dish detergent and you have a spray that will kill all kinds of bugs and fungal diseases.

One site includes this warning, “do not use this pesticide on edible crops. Though a good wash may remove the poison, I would not recommend testing it. And a reminder not to use it if you have dogs who may lick or chew the plants you are spraying.”

I guess the author is not as concerned about cats?

Since you can eat small amounts of rhubarb leaves I see no reason why it should not be sprayed on edible crops.

I could not find evidence that supports this claim; to be honest I did not look very hard. Insects do eat rhubarb leaves and boiling the leaves would only extract a minor amount of some of the chemicals present, producing what amounts to a homeopathic solution. Water is not a very good pesticide! If you disagree, bring me scientific evidence that it works.

Fun Facts

Try this link for more fun facts about Rhubarb.

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Rhubarb protection

Hi. Thanks for contacting Douglas County Master Gardeners. Here is some information from Iowa State University website that address your concerns. I hope this helps. If you have any more concerns please contact us again. Marlene Douglas County Master Gardener Link http://www.ipm.iastate.edu/ipm/hortnews/1997/5-2-1997/rhubarbsafe.html Safety Concerns about Rhubarb This article was published originally on 5/2/1997 Byline: by Richard Jauron, Department of Horticulture Many areas in Iowa experienced record or near record temperatures in early April 1997. Those cold temperatures have prompted questions on the edibility and use of rhubarb. Answers to those and several other rhubarb related health questions are presented below. Is it safe to use rhubarb after the plants have been exposed to freezing temperatures? The leaves of rhubarb do contain oxalic acid and soluble oxalates. Consumption of rhubarb leaves can cause nausea, vomiting, abdominal pains, and even death. The concern expressed by some individuals is that the oxalic acid and soluble oxalates would move from the leaves to the stalks upon exposure to freezing temperatures. In fact, however, the movement of these compounds into the stalks is not a problem. Gardeners should examine their rhubarb and base their harvest decision on plant appearance. Cold damaged rhubarb leaves will shrivel and turn black. Damaged stalks become soft and mushy. Damaged rhubarb stalks should be pulled and discarded. Any new growth which emerges later this spring would be safe to eat. Rhubarb plants showing no sign of damage are fine and can be harvested. Do the rhubarb stalks become poisonous by summer? It is generally recommended that home gardeners stop harvesting rhubarb in early to mid-June. Continued harvest through the summer months would weaken the plants and reduce the yield and quality of next year’s crop. The rhubarb stalks may become somewhat woody by mid-summer, but they don’t become poisonous. Is it safe to harvest rhubarb if the plant is flowering? While the flower or seed stalks should not be used, the leaf stalks are edible. However, the flower stalks should be promptly pulled and discarded. If allowed to develop, the flower stalks reduce plant vigor and next year’s production. Flower stalk formation may be caused by drought, infertile soils, and extreme heat. Age may be another factor. Old plants tend to flower more than young ones. Flower formation can be discouraged with good cultural practices. Water rhubarb plants once a week during dry weather. Sprinkle 1/2 cup of an all purpose garden fertilizer, such as 10-10-10, around each plant in early spring. Manure is an alternative to a commercial fertilizer. Apply a 2 to 3 inch layer of well-rotted manure around rhubarb plants in spring. Dig and divide large, old rhubarb plants in early spring or late summer. Are rhubarb leaves safe to put into the compost pile? While the rhubarb leaves do contain poisonous materials, they can be used in the compost pile. Oxalic acid and soluble oxalates are not readily absorbed by the roots of plants. Compost containing decomposed rhubarb leaves can be safely worked into the soil of vegetable gardens. This article originally appeared in the May 2, 1997 issue, p. 57. Year of Publication: 1997 Issue: IC-477(10) — May 2, 1997 by Richard Jauron, Department of Horticulture

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