Garden Myths - Learn the truth about gardening

Rhubarb Myths

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?

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.

References:

  1. The Poison Garden – Rhubarb; http://www.thepoisongarden.co.uk/atoz/rheum_x_hybridum.htm
  2. The Rhubarb Compendium; http://www.rhubarbinfo.com/content/rhubarb-varieties
  3. Photo source; Fluffymuppet

 

 

Robert Pavlis
Editor of GardenMyths.com
I live in southern Ontario, Canada, zone 5 and have been gardening a long time. Besides writing and speaking about gardening, I own and operate a 6 acre private garden called Aspen Grove Gardens which now has over 3,000 perennials, grasses, shrubs and trees. Yes--I am a plantaholic!

I hope you find Garden Myths an educational site that helps you understand your garden better.

3 Responses to 'Rhubarb Myths'

  1. tolga erok says:

    as usual, brilliant info!!!

  2. I once heard it said as a rule – ‘don’t eat Rhubarb after the first of July’ – not accompanied by an explanation

Please let me know what you think - Leave a Reply