Is it rhubarb? Work through the features
Answer five questions about the plant and get a safety-first verdict, because rhubarb leaves look a lot like dock and burdock.
How big are the leaves?
What is the stem like?
What colour is the stem at the base?
What does the top of the leaf look like?
Where is it growing?
The rule that keeps you safe
Eat only the stem. Never the leaf. This applies to garden rhubarb and to anything you think might be rhubarb.
And if you cannot positively identify a plant, do not eat it. That is not a cautious hedge, it is the actual rule, and it is the reason I built the key above rather than a photo tool. A photograph of a leaf someone is already unsure about is a weak piece of evidence, whereas a few questions about the stem and the leaf surface are much more reliable.
The features that identify rhubarb
| Feature | Rhubarb | Dock or burdock |
|---|---|---|
| Leaf size | Very large, up to a metre across | Large but usually smaller than a metre |
| Leaf surface | Smooth, slightly glossy, wavy margins | Puckered, crinkled and rough |
| Leaf underside | Pale green, smooth | Burdock is woolly and grey beneath |
| Stem | Thick, crisp, solid all the way through | Often hollow or spongy, or thin and woody |
| Stem colour | Deep red, or green with a red blush | Usually plain green, sometimes spotted |
| Growth | A basal clump from a thick crown, no main stem | An upright stem with leaves along it |
| Flowers | Tall pale greenish-white plumes in summer | Dock has small green-brown spikes, burdock purple thistle heads |
The stem is the strongest single clue
If you have a thick, crisp, solid stem that snaps cleanly and is red or red-blushed at the base, you almost certainly have rhubarb. Rhubarb petioles are genuinely solid, and they crunch like celery when you break one.
Dock and burdock stems are different. Dock stems are usually thinner and often hollow or spongy, and they grow from an upright flowering stem rather than a basal clump. Burdock has a deeply furrowed stalk with woolly hairs.
So the practical test is this: snap a stem. If it is solid, crisp and juicy, and the plant grows as a clump of leaves straight from the ground with no main stem, you are almost certainly looking at rhubarb.
Red is helpful, but not decisive
- Rhubarb varieties range from deep crimson through pink to almost entirely green.
- A green-stemmed plant can absolutely be rhubarb. Many older and hardier varieties are green with only a hint of red at the base.
- Do not reject a plant as rhubarb purely because the stems are green. Check the leaf surface and the stem cross-section instead.
- Conversely, red stems alone do not prove it is rhubarb. Some docks and sorrels have red or purple colouring too.
What I do with rhubarb
Strip the leaves and bin them, immediately, before anything else. Then wash the stems and cut off the dry base.
For most uses I roast it rather than stewing it. Cut the stems into lengths, toss with sugar and a little orange zest, and roast at 180 degrees for about twenty minutes. It holds its shape far better than a pot on the stove, which turns it to stringy mush.
The classic pairing is strawberry, and it works because the rhubarb is sharp and the strawberries are sweet. Rhubarb with ginger, orange or vanilla all do the same job. Rhubarb on its own needs a lot of sugar, and it is still sour.
Early-season stems in spring are the tenderest and the least sour. By late summer the stems get fibrous and the oxalic acid content rises, which is the origin of the old advice not to pick rhubarb after midsummer. It is not dangerous, just less pleasant.
This is the one plant in this series where a wrong answer can make you ill, so I want to be straight about it up front. Rhubarb leaves contain oxalic acid at a concentration that causes real harm, and they look a great deal like the leaves of burdock and broad-leaved dock.
That means the leaves that come with your rhubarb should go straight in the bin or the compost, never the salad bowl. It also means that if you are trying to identify a plant growing wild, you need to be more careful than a glance.
The good news is that the features are reliable once you know which ones to look at, and the stem alone will settle most cases.
Frequently Asked Questions
Check the stem first. Rhubarb stems are thick, crisp and solid all the way through, usually red or red-blushed, and the plant grows as a clump of large leaves straight from the ground with no main stem. Dock and burdock stems are often hollow or spongy and grow on an upright flowering stem.