Rhubarb container gardening means growing a single rhubarb crown (Rheum rhabarbarum) in a large, deep pot of at least 20 gallons / 75 L, sited in full sun and fed steadily, with the roots insulated through winter. Rhubarb is a big, long-lived perennial with a thick root system, so it needs far more room than most container crops. Get the pot size and the winter protection right, and a potted crown crops for years on a patio or balcony with no garden bed.
I keep a rhubarb crown in a half barrel by the back step, mostly because the open ground there is full of tree roots and nothing else will grow. It has lived in that barrel for six years now. The first spring it sulked and put up three thin stalks, and I left every one of them on the plant. By the third year it was throwing up thick red stems thick enough for a crumble, and it has done so every spring since. Patience at the start is the whole trick with potted rhubarb.
Why rhubarb needs such a big pot
Rhubarb is not a plant you can squeeze into a small container. In open ground a mature crown spreads a root system 3 feet / 90 cm across and just as deep, and it stays in the same spot for a decade or more. Confine that plant in a small pot and it stalls within a single season, putting up thin, mean stalks that are not worth pulling.
The minimum is 20 gallons / 75 L and 18 inches / 46 cm deep, which means a half barrel, a large planter, or a sturdy trug-shaped pot. Bigger is better here. The more soil volume the crown has, the more moisture and nutrients it can draw on, and the less often you are out there watering and feeding through summer. A half barrel of 25 gallons / 95 L is a good working target.
Drainage still matters despite the plant’s thirst. Rhubarb wants rich, moisture-retentive soil, but the crown rots if it sits in standing water all winter. Make sure the container has good drainage holes, and stand it on feet or bricks so water runs away freely rather than pooling under the base.
Rhubarb varieties for pots
| Variety | Stalk colour | Mature size | Hardiness | Notable |
|---|---|---|---|---|
| 'Victoria' | Green with red blush | 3-4 ft / 0.9-1.2 m | Zones 3-8 | Tried and true, heavy cropping, the classic forcing rhubarb, vigorous in a pot |
| 'Timperley Early' | Red, early | 2-3 ft / 0.6-0.9 m | Zones 3-8 | Earliest to crop, often ready in March, compact crown good for pots |
| 'Canada Red' | Deep red | 2.5-3 ft / 0.75-0.9 m | Zones 3-8 | Sweet red stalks, less fibrous than green types, excellent for pies |
| 'Glaskin's Perpetual' | Green-red | 2-3 ft / 0.6-0.9 m | Zones 3-8 | Can be harvested lightly in year one, lower in oxalic acid, slower to bolt |
| 'Raspberry Red' | Bright red | 2-3 ft / 0.6-0.9 m | Zones 3-8 | Sweet, tender stalks, classic for forcing, productive in a pot |
Planting a crown
Plant a single dormant crown per container in early spring or autumn. Fill the pot with a rich mix of good potting compost blended with garden compost or well-rotted manure, since rhubarb is a hungry plant that rewards a fertile start. A 2:1 ratio of loam-based compost to well-rotted manure suits it well. Set the crown so the growing buds sit just at the soil surface, not buried deep, or they may rot.
Site the pot in full sun. Rhubarb tolerates a little shade but crops best with at least 6 hours of direct light, which builds the strong stalks and good colour. A south or west aspect against a wall suits it well, and the wall also helps with winter shelter later on.
Water the crown in well at planting and keep the soil evenly moist through the first season. The plant is putting all its energy into establishing roots in its new home, so do not let it dry out. Mulch the surface with compost to lock in moisture and feed the soil as it breaks down.
The winter problem
Winter is the real challenge in rhubarb container gardening, and it catches people out. Rhubarb needs a spell of cold each winter to break dormancy and crop properly, so it is not a plant you can bring indoors to a warm room. It must stay cold. The trouble is that roots in a pot freeze far harder and faster than roots protected by the mass of the open ground.
In a zone 5 winter, an exposed pot can freeze solid right through, and a crown frozen that hard often dies. The roots, which would shrug off the same air temperature in the ground, are killed because the cold reaches them from every side of the container. This is the single most common reason a potted rhubarb fails to come back in spring. Rhubarb crowns need about 7 to 9 weeks at temperatures below 40 degrees F / 4 degrees C to break dormancy properly (Cornell University Garden-Based Learning), which is easy to provide in a pot, but only if the roots are not killed by a deep freeze.
The fix is insulation, not warmth. You want the crown cold enough to go dormant but protected from the worst of the deep freeze.
In my zone 5 garden the rhubarb barrel survives winter because I treat the pot, not the plant. Once the foliage dies back in autumn, I drag the barrel tight against the south wall of the house where it gets some warmth off the brick. Then I pile dry leaves around the sides, held in place with a length of chicken wire, and heap more over the crown. The leaves trap a layer of still air that stops the soil freezing solid. The first year, before I learned this, I lost a crown to a hard February freeze. Since I started insulating the barrel, it has come through every winter and cropped each spring.
Other methods work as well as leaf insulation. Sinking the whole pot into a spare patch of open ground for winter lets the surrounding earth buffer the cold. Grouping several containers tight together, with the rhubarb in the middle, means the outer pots take the brunt of the freeze. Wrapping the sides in hessian or bubble insulation slows heat loss. The aim with all of them is the same, to keep the root ball from freezing right through.
Feeding and watering through the season
A potted rhubarb exhausts its soil quickly because the plant is large and the soil volume is fixed. In the ground the roots range out for fresh nutrients, but in a pot they have only what you give them. Feed every couple of weeks through spring and early summer with a balanced liquid feed, easing off as the harvest ends.
Each spring, before growth starts, scrape off the top 1 to 2 inches / 2.5 to 5 cm of old soil and replace it with fresh compost or rotted manure. This top-dressing renews the surface feeding zone without disturbing the crown. Of all the yearly jobs, it does the most to keep a container crown vigorous over many years.
Water is the other constant demand. A big leafy rhubarb in a pot transpires hard on a warm day, and the soil dries faster than the same plant in open ground would. Keep the mix evenly moist through the growing season, and check daily in hot weather. Let it dry out repeatedly and the stalks turn thin and stringy.
Harvesting without weakening the crown
Restraint in the early years pays off for the life of the plant. Pull nothing the first year so the crown can build a strong root system in its new pot. In the second year take a light harvest, just a few stalks, and from the third year on you can harvest more freely.
When you do harvest, grip the stalk low down and twist it away from the crown rather than cutting it. Cutting leaves a stub that can rot back into the crown. Always leave at least half the stalks on the plant so it keeps photosynthesising and feeding the roots, and stop pulling by midsummer to let the crown recover and store energy for next year. A mature potted rhubarb yields 2 to 3 lb / 1 to 1.5 kg of stalks per year, less than a ground bed but plenty for a few crumbles.
Never eat the leaves. Rhubarb leaves contain high levels of oxalic acid and are toxic, so trim them off and compost them, using only the stalks. The leaves break down fine on the compost heap despite being poisonous to eat. The oxalic acid decomposes along with the leaf tissue in a hot compost, so the heap stays safe.
Dividing a tired crown
After 4 to 5 years a potted crown often fills its container and starts to lose vigour, throwing up thinner stalks and crowding its own roots. This is the cue to divide. In autumn or early spring, tip the crown out of the pot and cut it into sections with a spade, each section carrying at least one strong bud and a chunk of root.
Replant the healthiest section in fresh, rich mix in the same cleaned pot, and pot up or give away the spares. Division renews the plant completely. A crown that was flagging will crop with new energy once it has fresh soil and room to grow, which is why a single rhubarb plant can effectively last forever through repeated dividing.