At a glance
- Rhubarb is a perennial for life: planted well once, a crown keeps yielding stalks for 15 to 20 years.
- Harvest runs from roughly CW 14 to CW 26, so from early April to 24 June (Midsummer, St John's Day).
- Always pull and twist the stalks, never cut them. A clean pull heals faster than a cut wound.
- Stop harvesting after Midsummer: the oxalic acid content rises, and the plant needs strength for winter.
- Every 8 to 12 years, divide the rootstock in autumn or early spring. That rejuvenates and propagates in one go.
There are few plants in the garden that ask for so little and give so much as rhubarb. You plant it just once, give it a handful of compost in spring, and in return it pushes up its thick, tart stalks year after year, often long after the gardener who planted it has stopped coming to the garden. An old crown in the corner of a bed is no accident, it is an heirloom. And to keep it that way, three things are worth getting right: plant it right, harvest it right, and divide it in good time.
Why rhubarb is a perennial for life
Botanically, rhubarb, Rheum rhabarbarum, is closely related to sorrel and belongs to the knotweed family. What you harvest are the leaf stalks, not the leaves, and that is exactly what makes it one of the longest-lived crops in the kitchen garden. It grows from a strong, woody rootstock that widens year by year and digs deep into the soil.
This endurance comes at a price: rhubarb is a heavy feeder and needs room. A mature crown takes up a good 80 to 100 cm square, and anyone who plants it too close to its neighbours will regret it in five years. Plan generously and you will have peace for a long time.
Because it stays in the same spot for so long, choosing the site is the single most important decision. A partly shaded to sunny place with deep, humus-rich soil is ideal. It dislikes waterlogging and lasting drought in equal measure. If you are laying out a new bed anyway, that is the moment to enrich the soil thoroughly with mature compost, because later you cannot reach that depth again.
Site and planting: get it right once, then for decades
The best planting time is autumn, roughly from late September to October, or alternatively early spring in March before growth starts. You can get rhubarb either as a potted plant or, more traditionally, as a division from a neighbour's garden. Both work, and the division is the more honest route because you know the variety.
Dig a generous planting hole
Dig a hole at least 40 cm wide and deep. Loosen the soil well at the bottom so the strong root can grow downward.
Work in compost
Mix mature compost and a handful of horn shavings into the excavated soil. Rhubarb is hungry, and this store carries it through its first years.
Set the bud just below the surface
The fat growth bud (the eye) belongs at soil level or at most 2 to 3 cm below it. Planted too deep, the crown rots; too high, it dries out.
Water in and mulch
Water thoroughly, then lay a mulch layer of grass clippings or straw. It holds moisture and feeds the plant as it rots down.
Do not harvest in the first year
Hard as it is, leave the stalks standing in the planting year. The plant needs to root in first. From the second year you take a few gently, from the third you can help yourself.
Rhubarb is fully hardy and survives frost down to around minus 20 degrees without protection. The foliage dies back in autumn, the rootstock rests and pushes out fresh growth in spring. Only young plants in their first year get a loose cover of leaves or brushwood. Rhubarb in pots is more frost-sensitive at the roots and belongs sheltered against a house wall.
Harvesting by hand: pull, don't cut
This is where the allotment gardener parts ways with the supermarket. Rhubarb stalks are not cut off, they are pulled. You grip the stalk as low as possible, close to the ground, and pull it out sideways with a slight twist. It comes away cleanly from the leaf sheath, with a small white foot at the end.
Why is this better than a knife? A cut leaves a stub sitting in the moist crown, which rots and carries decay into the rootstock. The clean pull, by contrast, heals quickly and dry. Never take more than half a plant's stalks at once, so it keeps enough leaf mass for photosynthesis.
What you cut from rhubarb, you take from it. What you pull, it gives you.
Old gardener's rule
The leaves come off, and straight away. They contain far more oxalic acid than the stalks and do not belong on the plate. On the compost heap they are perfectly fine, where the acid breaks down without trouble. Some gardeners also lay the big leaves as a mulch between the bed rows, where they block the slugs' path for a while.
Rhubarb leaves are not fit to eat because of their high oxalic acid content and can cause nausea in quantity. Use only the leaf stalks, peeled or unpeeled, never the leaf blade. For children the rule is: the stalk yes, the leaf never.
The Midsummer rule: why 24 June is the cut-off
The most important number in the rhubarb year is 24 June, Midsummer or St John's Day. Depending on the year it falls in CW 25 or CW 26 and marks the end of the harvest. This rule is no superstition; it has two solid reasons.
First, the oxalic acid content in the stalks rises noticeably as the season goes on. What tastes mildly tart in April turns sharp by high summer and unpleasant for sensitive stomachs. Second, and this is the real point, the plant needs the second half of the year for itself. From Midsummer it gathers strength in the rootstock through its leaves, sets new buds and prepares for winter and the vigorous new growth next spring. Harvest past Midsummer and you weaken the crown, and you will notice it in thinner stalks the following year.
After Midsummer, then, you let the plant grow in peace. The remaining leaves are now its food factory. After the last harvest, give it a second helping of compost or well-rotted manure, spread flat on the surface, not dug in, because the roots lie just below the soil. This summer feed is the key to a strong spring.
Dividing the crown: rejuvenation and propagation in one
After about 8 to 12 years the vigour fades. The stalks get thinner, the centre of the crown turns woody and barely grows. That is no reason to throw it out, it is the signal to divide. Root division is at the same time the most reliable way to propagate rhubarb, because only this keeps the variety true to type.
Choose the timing
Best in autumn, as soon as the leaves yellow (late September to October), or in early spring before growth starts in March.
Lift the rootstock
Cut around it generously and lift the whole ball out of the soil with a digging fork. Shake off coarse soil so you can see the buds.
Split into fist-sized pieces
With a sharp spade, cut the crown into sections. Each piece needs at least one strong growth bud and a good length of root. Throw away the woody, budless core in the middle.
Replant fresh
Set the divisions like a new planting in a new spot, bud just below the surface, water in, mulch. In the first year after division, again do not harvest.
Care through the year at a glance
- Spring: feed with compost
As soon as the first buds push (around March), spread mature compost and horn shavings flat on the surface. Do not dig it in; the roots lie just below the soil.
- Break out flower stalks
If the crown pushes up a thick flower stalk, break it out early and low. If the plant flowers, it puts its energy into seed instead of stalks.
- Summer: water evenly
Rhubarb has a high water demand. In dry spells, water deeply, better rarely and plenty than often and little. Mulch holds the moisture.
- Winter: simply leave it
Cut back the dead foliage only before growth starts in spring, not already in autumn. The crown survives winter without protection.
Varieties and what ends up in the kitchen
Green or red is not a question of ripeness but of variety. Green-stalked kinds like Rhabarber 'Goliath' are especially productive and strong in flavour. Red-stalked, red-fleshed kinds like Rhabarber 'Holsteiner Blut' taste milder, less sour, and turn compote and cake a pretty pink. If you have the choice, plant both: the green for quantity, the red for looks.
In the kitchen, rhubarb is a shape-shifter. Classic as compote, in crumble cake, as a syrup for summer lemonade, or savoury with meat. An old trick against too much acidity: a pinch of baking soda in the cooking water binds some of the oxalic acid and saves sugar.
Rheum rhabarbarum
- Familie
- Knotweed family (Polygonaceae)
- Standort
- Partial shade to sun, deep, humus-rich
- Saison
- Harvest April to 24 June · CW 14 to 26
- Wasserbedarf
- High, evenly moist
- Frosthärte
- Hardy to about minus 20 degrees
Frequently asked questions about rhubarb
Frequently asked questions about rhubarb
Why pull rhubarb instead of cutting it?
When you pull, the stalk comes away cleanly from the leaf sheath and leaves a dry, quickly healing wound. A cut leaves a stub in the crown that can rot and carry decay into the rootstock. Grip the stalk close to the ground and pull it out sideways with a slight twist.
Until when can I harvest rhubarb?
Until 24 June, Midsummer or St John's Day, which is roughly CW 25 to 26. After that the oxalic acid content rises, and the plant needs the second half of the year to gather strength in the rootstock through its leaves. Harvest longer and you weaken the crown and get thinner stalks the next year.
Are rhubarb leaves poisonous?
The leaves contain far more oxalic acid than the stalks and are not fit to eat. In larger amounts they can cause nausea. Eat only the leaf stalks, never the leaf blade. On the compost heap, though, the leaves are perfectly fine.
When and how do I divide an old rhubarb crown?
When the stalks get thinner after 8 to 12 years and the centre turns woody, it is time. Lift the rootstock in autumn (late September to October) or in early spring (March) and split it with a spade into fist-sized pieces. Each piece needs at least one strong bud. Throw away the woody core.
Can I harvest in the planting year already?
No. In the first year the plant needs to root in, so you leave all the stalks standing. From the second year you take a few gently, from the third you can harvest normally. This patience pays off with a strong, long-lived crown.
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