How to Grow Rhubarb: Planting, Harvest and Dividing

Rhubarb quick facts

On this page

• Rhubarb quick facts
• The spot you pick now stays picked for twenty years
• Crown division or potted plant — and spring or fall?
• How to plant rhubarb step by step
• Why can't you harvest rhubarb the first year?
• Zone chart: planting, first harvest, picking window and dividing in USDA zones 3–6
• How do you harvest rhubarb properly?
• When should you stop harvesting rhubarb?
• Flower stalks: snap them off immediately
• Forcing under a bucket for early pink stalks
• Dividing old crowns every five to six years
• Oxalic acid: why the leaves are never eaten
• Rhubarb varieties for cold climates
• Year-round care
• Crown rot, bolting and other problems
• Common mistakes
• Frequently asked questions

The spot you pick now stays picked for twenty years

Rhubarb is not a vegetable you shuffle between beds. The plant builds a coarse, woody crown that after five years can be wider than a bucket and reach 50 cm (20 in) down. That is also why rhubarb has no place in your crop rotation — you set it outside the system and plan the annuals around it.

Light

Rhubarb wants sun but tolerates part shade, which is unusual for an edible. Four to six hours of direct sun gives a full crop. In baking afternoon sun on dry sandy soil the stalks turn stringy early, because the plant hits water stress just when it should be swelling. Morning sun with midday shade often beats the hottest spot.

Drainage

This is the one factor that genuinely kills plants. Rhubarb handles cold without complaint, but a crown sitting in standing meltwater in March rots from the inside. Avoid hollows where snowmelt pools, hardpan clay and the strip under a downspout. On heavy clay a raised bed is the answer — see the guide to raised bed gardening, and lift it 25–30 cm (10–12 in) so winter water drains away.

Space and soil prep

A mature plant spans 120–150 cm (4–5 ft) and shades everything within a metre. Put it along the north edge of the bed, not in the middle over newly sown rows.

Soil preparation is a one-time opportunity: once the crown is in, you never reach the ground beneath it again. Dig a hole 50 × 50 cm (20 × 20 in) and 40 cm (16 in) deep, loosen the bottom with a fork, and mix 20–30 litres (5–8 US gal) of well-rotted manure or compost into the backfill. A bed that grew potatoes last season is already deeply loosened.

Crown division or potted plant — and spring or fall?

Three routes lead to a plant, and they differ more in time than in price.

Crown division. A chunk of woody crown with two or three visible buds and a good mass of root is the fastest and cheapest start. It is a clone, so you know what you are getting, and it establishes quickly because the reserves are already there.

Potted plant. Costs more but can go in any time in the growing season. The advantage is that you see what you buy. The drawback is that potted stock is often younger and smaller than a division of the same cultivar.

Seed. Possible, but it costs an extra year and gives no varietal consistency — rhubarb is cross-pollinated, so seedlings vary in colour, earliness and acidity. 'Victoria' and 'Glaskin's Perpetual' are sold as seed.

Spring or fall?

Spring planting is the standard recommendation in cold-climate North America, and extensions in Iowa and Utah both name it as the preferred window: plant as early as the ground can be worked, while the roots are still dormant. Safer in zones 3–4 and on heavy soil. The cost is that the plant must establish and build leaf at once, through early-summer dry spells, so watering the first summer is not optional.

Fall planting works well where winters are not extreme. Put the crown in once the leaves have died back but while the soil is still warm — roots grow on when shoots have stopped — and it starts from a stronger position the following spring. Two requirements: four to five weeks in the ground before it freezes solid, and genuinely free-draining soil. A fresh division sitting in wet clay all winter is the commonest way to lose one.

How to plant rhubarb step by step

1. Clear every scrap of perennial weed first. Couch grass or bindweed growing into the crown cannot be removed later — this is the only time you have access.
2. Dig the hole 50 × 50 cm (20 × 20 in) and 40 cm (16 in) deep. Break up the bottom with a fork so roots can go down.
3. Mix the backfill with 20–30 litres (5–8 US gal) of well-rotted manure or compost. Fresh manure against the crown can scorch the buds — put it in the base with 10 cm (4 in) of soil over it.
4. Set the division buds up. The buds are pink to deep red and fingertip-sized, and should end up 3–5 cm (1–2 in) below the finished surface. On wet or heavy clay, leave the topmost buds level with the surface instead — the Royal Horticultural Society notes this markedly reduces rot risk.
5. Backfill and firm it in. No air pockets around the root mass. A potted plant goes in at the depth it sat in the pot.
6. Water generously, 10–15 litres (3–4 US gal), even in fall and even if it is raining — the water settles soil around the roots.
7. Mulch around, never over, the buds. Lay 5–7 cm (2–3 in) of compost, grass clippings or straw in a ring, a hand's width clear of the crown. Mulch on the crown holds it wet and invites rot.
8. Label the spot. A fresh crown is invisible above ground for months, and a spade through it in April ends the project needlessly.
9. Water weekly the first summer. 15–20 litres (4–5 US gal) in dry spells. Established plants look after themselves; a first-year plant has no root system to draw on.

A well-kept plant yields 2–5 kg (4–12 lb) of stalks a year from year three — ten to twenty pies. Two plants cover a household, three if you make jam and freeze.

Why can't you harvest rhubarb the first year?

This is the rule most often broken, and it costs more than it looks.

Rhubarb is harvested by taking leaf stalks — the plant's photosynthetic machinery. Every stalk you pull carries a large leaf that would have gone on making sugar, and that sugar is stored not in the stalk but in the crown below ground. The crown is the plant's entire capital, and it sets how thick next year's stalks will be. A new crown has almost none: a chunk of root, a few buds and one summer. Harvest in year one and you remove exactly the leaves meant to fund the next twenty years. The plant rarely dies, but stays permanently weaker — thin stalks, early bolting, dividing needed at five years instead of ten.

• Year 1: nothing at all. Let every leaf stand until it dies back on its own. Do snap off any flower stalk.
• Year 2: two to four stalks per plant, once. Take the thickest, in late spring. If the plant looks weak, skip year two as well.
• Year 3: a four-week harvest. Iowa State Extension puts year three at roughly four weeks, then eight to ten weeks from year four.

The same applies after dividing or moving. In zone 3 establishment is slower, so wait until year three for the first light picking.

Zone chart: planting, first harvest, picking window and dividing in USDA zones 3–6

Rhubarb is hardy throughout this range, so the zone says nothing about survival — what it sets is the timing. A shaded north-facing site or cold clay behaves like one zone colder.

Two patterns are worth remembering. The harvest window shifts about six weeks between zone 6 and zone 3 but does not get much shorter — long northern days drive growth hard in June. And the fall window closes earlier the colder the zone: in zone 3 early September is the last call, because a crown set later cannot anchor itself before the ground freezes.

How do you harvest rhubarb properly?

Rhubarb is never cut with a knife or secateurs. That is not a matter of style but of rot.

Pull and twist

Grip the stalk as low as you can reach and pull upward while twisting slightly to one side. It releases with a small snap at its attachment on the crown and comes away whole. If it will not budge, twist more and pull less.

Cut the stalk instead and you leave a stub that rots. The RHS specifically advises against cutting, because that stub becomes an entry route for rot straight down into the crown. A pulled stalk leaves a clean break that dries within a day.

Leave at least a third

Never take more than one third to one half of the stalks at a single picking, and make sure the plant keeps at least a third of its leaf area — never fewer than four or five leaves. The leaves pay the harvest back. The RHS puts the limit at a third per picking, Ohio State Extension at one third to one half. Pick little and often rather than stripping the plant.

Which stalks, and what about the leaves?

Take the outer stalks, which are oldest and thickest, and leave the small ones in the centre. A ready stalk is 25–40 cm (10–15 in) long, at least thumb-thick and firm when squeezed. Thin stalks late in the season are the plant telling you it has had enough.

Snap the leaf blade off at the plant — it never comes into the kitchen, and a leaf left attached draws moisture out of the stalk. Unwashed stalks keep three to five days in the crisper drawer in a bag. To freeze, cut into 2 cm (3/4 in) pieces and freeze straight away, no blanching needed.

When should you stop harvesting rhubarb?

Two conflicting answers circulate, and both have a point.

The extension answer is a fixed date. Iowa State puts the end of the season at mid-June, the RHS at late June or early July, and the Old Farmer's Almanac at eight to ten weeks ending around midsummer. The reason is not that rhubarb becomes dangerous — the plant needs the rest of the summer to refill the crown, and every leaf left standing works for next season.

The other line, common among experienced growers, is to keep going as long as the plant looks vigorous and produces thick stalks. That does work on an old, happy plant in good soil. Rhubarb does not bolt and finish like an annual; it keeps making new stalks all summer.

So read the plant rather than the calendar:

• Stop when the stalks get thin. If new stalks are noticeably narrower than the May crop, the plant is running on reserves. That is the end, whatever the date.
• Leave ten to twelve weeks of full leaf before first frost. In zone 5 that means late June, in zone 3 mid-July.
• Make the final picking the lightest of all — after that, every leaf stays.
• Exception for late cultivars. 'Glaskin's Perpetual' and similar long-season types tolerate a longer picking period.

Flower stalks: snap them off immediately

Some time in June the plant sends a thick, round stalk straight up from the centre, coarser than the leaf stalks and topped by a tight, cabbage-like bud. It opens into a plume of creamy-white flowers up to 1.5 m (5 ft) tall. Handsome, and it has to go.

A flowering rhubarb puts energy into setting seed rather than into stalks and crown. The crop drops that season and the plant enters winter weaker. Snap the flower stalk off as soon as you see it, while it is short and tender — grip it low and twist it off like a harvest stalk. If it has turned woody, cut it cleanly at the base rather than leaving a long stub.

An occasional flower stalk is normal, especially on older plants and after a warm dry spring. But a plant that bolts year after year, or throws three or four stalks at once, is old, crowded, dry or hungry — the clearest sign that the crown needs dividing. Variety matters too: 'Barbro' and 'Berit', bred at Balsgård in Sweden, were selected for low flowering tendency.

Forcing under a bucket for early pink stalks

This is the most enjoyable trick in rhubarb growing, and almost nobody does it. Forcing means covering a bud that has just started to move and letting the plant shoot in total darkness. The result is pale pink to bright red stalks, slender and sweet enough to need less sugar, three to six weeks ahead of the normal crop.

1. Pick a vigorous plant at least three years old. A young or weak crown cannot take it.
2. Wait until the dark red buds just show above ground. In zone 6 that is February or March, in zones 3–4 April. Cover earlier and you simply get cold weeks under the bucket.
3. Invert a bucket, bin or terracotta forcer over the bud. A black mortar tub works just as well. Block any holes — it must be completely dark — and weigh it down with a brick.
4. Pack leaves or straw around the outside for a few degrees of insulation. Fresh stable manure packed around it generates heat as it breaks down and lets you start weeks earlier.
5. Check after three weeks. The stalks are ready at 25–30 cm (10–12 in), filling the bucket. Reckon on three to six weeks; the RHS gives four to eight for the earliest starts.
6. Harvest the lot at once and lift the cover. Then let the plant rest for the season.

The important limit: do not force the same plant two years running. Forcing drains the crown hard — the plant pushes growth on stored energy with no light at all — and the RHS is explicit about it. With two or three plants you rotate, and whichever was forced gets no further harvest.

Dividing old crowns every five to six years

A rhubarb that is never divided becomes a dense knot of competing buds. Stalks get more numerous but thinner, the centre dies out into a hollow ring, and flower stalks arrive earlier each year. Dividing every five to six years prevents all of it — the RHS gives roughly five years for congested clumps, Wisconsin every fourth or fifth year. And you get free plants: a mature crown yields five to ten new ones.

Divide while dormant — early spring before the buds break, or late fall once the leaves have died down. Spring is safer in zones 3–4, and the best moment is just as the buds appear and frost has left the soil.

1. Water the plant the day before if the soil is dry, so the root mass holds together.
2. Cut around the plant about 30 cm (12 in) out from the centre and lever the crown up. It is heavier than it looks — a ten-year-old plant can weigh 20 kg (45 lb) with soil on.
3. Wash the soil off so the buds show — dividing blind is guesswork.
4. Split with a spade, axe or heavy knife. The crown is hard and woody and should crack audibly. Each piece needs at least one bud, ideally two or three, and a substantial root. A piece smaller than a fist establishes slowly.
5. Discard the dead centre — soft, brown or hollow tissue makes no new plant.
6. Replant immediately in a freshly improved hole, on a new site if you can. Hold spare pieces cool and damp in newspaper if you must wait.
7. Harvest nothing that season — normal picking resumes the year after.

If the plant needs moving, dividing is the moment — the move costs a season's harvest either way. Rhubarb is also one of the most rewarding perennials among the best raised bed crops.

Oxalic acid: why the leaves are never eaten

Rhubarb is the only common garden plant where you harvest one part and throw the other away. It is worth explaining properly, because it gets both overstated and understated.

Oxalic acid is present throughout the plant but heavily concentrated in the leaf blade. Chemical summaries put the blade at around 0.5 g per 100 g, while the level in the leaf stalks — the part you eat — is low enough that the RHS states the amount in the stems is insufficient to have a toxic effect. Oxalic acid also occurs in spinach, chard, nuts and tea.

Eat the leaves and the symptoms are burning in the mouth and throat, nausea, vomiting and abdominal pain. The estimated lethal dose of oxalic acid sits around 15–30 g, which corresponds to several kilograms of leaf in one sitting. Curiously, post-mortems in the historical deaths attributed to rhubarb leaves found no oxalate, which has led researchers to other compounds — anthraquinone glycosides among them. The conclusion is the same: the leaves are not eaten. Not in pesto, not as a spinach substitute, not fed to chickens.

Compost them instead — the oxalic acid breaks down, and the blades are large, wet and nitrogen-rich. They also work as a sheet mulch: lay them face down around the plant, where they smother weeds for a few weeks.

And the myths: no, rhubarb does not become poisonous after midsummer. The level in the stalks rises slightly, but what changes is texture — they get stringier, a flavour question rather than a health one. No, frosted rhubarb is not dangerous, though frost-damaged stalks go soft and are simply poor. And no, you do not peel rhubarb for safety.

Rhubarb varieties for cold climates

Variety choice sets three things you cannot change afterwards: earliness, colour and acidity. These are the cultivars most often recommended for zones 3–6.

With room for three plants: one very early variety to force, one workhorse such as 'Victoria' or 'Crimson Red', and one deep red type for colour in jam. For the lowest acidity, 'Glaskin's Perpetual' and the Balsgård cultivars are the ones named for it.

Year-round care

Rhubarb is a heavy feeder that is almost never overfed. Care is mostly putting back what you took out.

Spring and early summer

Rake last year's dead leaf debris off the crown, then lay 10–20 litres (3–5 US gal) of well-rotted manure or compost in a ring around the plant, from a hand's width outside the buds to half a metre out — never over the crown. Where manure is impractical, Iowa State suggests half a cup of general garden fertiliser per plant in early spring.

Through the picking season, snap off flower stalks, harvest every couple of weeks and keep weeds out within a metre — perennial weeds in the crown become permanent. A ring of mulch handles weeds and moisture.

High summer

Now the plant is rebuilding, and water is the only requirement: 20–30 litres (5–8 US gal) per plant per week in dry spells. Drought stress in July is the commonest cause of thin stalks the following spring.

The large plant shades everything near it, which you can put to work. A row of lettuce on its east side stays crisp into July when the same sowing in full sun has bolted — exactly the thinking behind companion planting.

Fall and winter

Let the leaves die back and remove them only once brown and soft; the plant withdraws nutrients from them until the end. Apply 5–10 cm (2–4 in) of compost or leaves as a fall feed, keeping the crown clear. Winter protection is not needed in zones 3–6 — rhubarb requires a cold dormancy to shoot properly. Containers are the exception: a pot that freezes solid for weeks can lose the crown.

Common mistakes

• Harvesting in the first year. Those leaves build the crown. A plant picked in year one stays permanently weaker.
• Cutting stalks instead of pulling them. The stub rots and the rot can travel into the crown. Always pull and twist.
• Taking too many stalks at once. Leave at least a third of the leaf area, never fewer than four or five leaves.
• Planting too deep. Buds belong 3–5 cm (1–2 in) under the surface, and level with the surface on wet clay. A crown that gets buried or mulched over rots.
• Choosing a badly drained spot. Rhubarb shrugs off cold but not standing water. The hollow where meltwater collects is wrong for twenty years.
• Forgetting the plant in July. Drought during the rebuilding phase means thin stalks next spring.
• Never dividing. After ten years the centre is often dead and the stalks thin.

Frequently asked questions

When should you plant rhubarb?
Plant in early spring as soon as the ground can be worked, while the crown is still dormant — the preferred window in zones 3–4 and on heavy soil. Fall planting also works where the ground freezes late: set the crown once the leaves have died back, four to five weeks before it freezes solid.

How deep do you plant rhubarb crowns?
Set the buds 3–5 cm (1–2 in) below the finished soil surface, pointing up. On wet or heavy clay, leave the topmost buds level with the surface instead, which markedly reduces rot risk. A potted plant goes in at the depth it sat in the pot. Planting too deep, or mulching over the crown, is a common cause of crown rot. Spacing is 90–100 cm (3 ft).

Why can't you harvest rhubarb the first year?
Because the leaves are the plant's only way of building the crown, and the crown sets how thick the stalks will be for twenty years. A new crown has almost no reserves. Harvest nothing in year one, take two to four stalks once in year two, then four weeks in year three and eight to ten weeks from year four.

Should you pull or cut rhubarb?
Pull, always. Grip the stalk near the soil line, pull upward and twist slightly so it releases at the base. A cut stalk leaves a stub that rots and can let rot into the crown — the RHS specifically advises against cutting. Snap the leaf blade off at the plant and compost the blades.

How much rhubarb can you pick at once?
One third to one half of the stalks per picking, always leaving at least a third of the leaf area — never fewer than four or five leaves. Take the outer, thickest stalks and leave the small ones in the centre. An established plant handles picking every couple of weeks, which yields more than one big strip.

When should you stop harvesting rhubarb?
Extensions give mid-June to early July, but the plant is a better guide than the calendar: stop when new stalks are noticeably thinner than the spring crop. Leave ten to twelve weeks of full leaf before first frost so the crown can refill. Long-season varieties such as 'Glaskin's Perpetual' tolerate longer picking.

Are rhubarb leaves poisonous?
Yes, and they must never be eaten. The blade carries around 0.5 g of oxalic acid per 100 g plus other compounds suspected of contributing to toxicity, and no cooking removes the problem. Symptoms are a burning mouth, nausea and abdominal pain. The stalks are entirely safe — the level there is too low to have any effect.

How often should you divide rhubarb?
Every five to six years, or when the plant throws many thin stalks, bolts every year and has started dying out in the centre. Divide while dormant, in early spring or late fall. Lift the crown, wash the buds clear and split into fist-sized pieces with two or three buds each. A mature plant gives five to ten new ones.

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