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.
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.
Rhubarb – Fruit or Vegetable?
Botanically rhubarb is a vegetable but in the US it’s classified as a fruit.
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.
- They tend to get woody in late summer and don’t taste as good.
- 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.
References:
- The Poison Garden – Rhubarb; http://www.thepoisongarden.co.uk/atoz/rheum_x_hybridum.htm
- The Rhubarb Compendium; http://www.rhubarbinfo.com/content/rhubarb-varieties
- Photo source; Fluffymuppet
The best rhubarb plants I had grew from seeds I just sprinkle them on the black dirt raked and water them every day until they were well established.
I planted my rhubarb plants without fencing and after a couple of months of little to no munching, someone is going to town on my rhubarb leaves. We have lots of deer and groundhogs so I’m not sure who the culprit is but they are eating the leaves only and leaving the stalks! My question is whether these plants will come back next year as they were planted this Spring. I’m in zone 6b.
probably – they are tough plants.
I planted rhubarb crowns that had been dug out in fall, dumped on plastic sheets so parts were sometimes soaking for days/weeks and forgotten over winter. Found and planted them in February, covered with compost & chicken manure pellets and got a great harvest for years
My mom has said that you can harvest rhubarb only in months that have no R in their name ei May, June, July and August. Saying that in southern Ontario Canada usually by end of June our plant is done producing viable stalks
What if you live in Australia?
I apologize for two comments, but it just dawns on me that you said “Continual harvesting will eventually kill the plant.” It so happened that three seemingly healthy plants died on me within a year. This isn’t strange per se, I manage to kill plenty vegetables with my gardening skills, but what makes rhubarb so interesting is that the plants die within a day. One day they are perfect, the next day the entire plant is flat on the ground and rotting. One postmortem revealed a root that went to mush, but if I recall correctly at least one website mentioned that rhubarb sometimes has mushy roots.
Rhubarb is possibly my favourite vegetable, because it goes into rhubarb crumble pie, so my question is, do you think I harvested too much? I always leave at least 4 leaves per bud.
Don’t harvest more than half the plant.
I like to freeze some in the spring for use later. I keeps well. I just put 2 cups in a freezer bag and squeeze the air out and close the bag. It will keep at least year.
I had woolly lice on my tomato plants and a serious infestation of white fly on my pomegranate. I treated both with a mixture of rhubarb leaf extract, as instructed on the Net, and neem oil. Both pests are gone, and white fly is apparently a very difficult pest to get rid of. Neem oil works, that’s why I have it, but its effect was supercharged by the rhubarb leaves. I for one believe in them.
You may believe – but based on your description of your testing process you did not use controls. Without a control you can reach no conclusions.
My rhubarb, which I planted last summer, is starting to flower. I’m assuming it is planning on producing seeds. Can those seeds be used to plant? Would they just go in soil or do they need special treatment?
Never started rhubarb seeds, but it might be worth the effort. Most rhubarb are from selected clones and you probably get better plants with division.
Hi Robert.Are ‘forced’ rhubarb leaves any easier to consume?
I don’t know. Forced rhubarb is usually harvested before leaves fully develop, so you don’t end up with forced leaves.
as usual, brilliant info!!!
I once heard it said as a rule – ‘don’t eat Rhubarb after the first of July’ – not accompanied by an explanation
Rhubarb is better for eating early in the season – it tends to get woodier later. But there is no reason not to eat it all season long.