how to plant, grow & care for rhubarb
complete growing guide
As the last of the pears and apples get eaten, rhubarb takes over and gives us delicious things for pudding until the strawberries start. Once established, rhubarb will grow happily in the same spot year after year, just needing the occasional mulch to keep it happy. It can cope with shade, and you can even use a rhubarb forcing pot to get a super tender and sweet early crop. A rhubarb glut can also be preserved as jam, compote or turned into colourful cordials and liquors.
- Common name Rhubarb
- Latin name Rheum x hybridum
- Type Hardy Perennial
- Height & spread 75cm x 1m
- TLC rating Easy
- Aspect Full sun/partial shade
- Spacing 1m
- Yield 5kg
- Suitable for pots Yes
- Grow in a greenhouse? No
how to grow rhubarb
where to grow rhubarb
Soil type: A neutral, fertile well drained soil is preferred, as rhubarb hates being waterlogged in winter.
Aspect & Position: Choose an open, sunny site avoiding frost pockets and find an area which has not grown rhubarb in the last six years. If you are growing it in the border allow plenty of space as it will shade out other plants in the summer. If you have a more shaded spot rhubarb will grow, but it won’t be quite as productive.
when to plant rhubarb
New rhubarb crowns can be planted any time when the plant is dormant, so generally from November to March.
how to plant rhubarb
When you receive your bare root plants, pot them on with the growing point at, or just below the soil surface. Grow them on for about a month until the roots have filled the pot.
Prepare the area where you plan to plant the crown by forking in plenty of well-rotted organic material. Plant the crowns no more than 5cm below the soil surface, taking great care not to break any of the newly formed roots.
Don’t harvest anything in the first season. Just mulch your plants – not too close to the crown - and let them grow and establish themselves well. Simply allow the sticks of rhubarb to die back in the first autumn.
how to care for rhubarb
Rhubarb will not need watering once it is established – the roots go down deep into the ground to find the available moisture. If the spring is very cold and dry, however, a stressed plant can send up a rather impressive flower spike, showing how it is keen to run to seed and propagate itself. If that happens, remove the flowering spike straight away and water if drought seems to be the problem. If you are growing rhubarb in a pot, you will need to give it a good drink every week whilst it is in leaf.
As rhubarb is in for the long haul you need to make sure it is planted in fertile ground. From then on, an autumn mulch should keep it in fine fettle, as long as you do not over crop each plant.
growing in pots
Rhubarb can also be planted in very large pots at least 50cm deep and wide. You will need a fertile loam-based compost (John Innes Number 3), and you will need to water regularly whilst the plant is in active growth. Place your containers in full sun.
In the second season (12-14 months after planting), you can start picking when the leaves have fully unfurled and the stems are approximately 30cm long. Never take more than half of the stems at a time – over-cropping will reduce the plants vigour. Stalks are harvested by gently twisting the stems and pulling from the base of the plant. If you grow a good range of early, medium and late varieties you can have a harvest from early spring to late summer.
lifting & dividing
Lift and divide the crowns every 5 or 6 years, between November and March while the plant is dormant. Use a spade to lift each crown, split into 3 or 4 pieces and replant separately. Make sure each piece has a healthy-looking bud, which will become the growth point for next year’s new shoots. Remember the leaves are poisonous to eat but can be safely composted with the rest of your garden waste.
A mature plant can be “forced” to give you a very tender “blanched” crop that will hardly need any sugar. In the old days (and still in the forcing houses of Yorkshire), whole plants were dug up in the autumn and moved indoors to warm dark sheds where they start cropping in the middle of winter. You can try this yourself, especially if dividing an elderly crown anyway, but it does mean sacrificing that section, as they will rarely return from such harsh treatment. However, there is a half-way house, using a fancy terracotta forcing pot, or more prosaically, an upturned bucket.
Early in the new year, select a healthy two- or three-year-old plant and place the forcer over it, surrounding the crown with dry straw or bracken to create some warmth. Replace the lid and watch out over the next seven to eight weeks for the emerging shoots pushing off the lid to show how they are ready to be picked. Pick all the stems off every week until your unforced plants begin to take over in late spring. Remove the forcer and the straw and give the plant a good mulch of well-rotted compost. Do not take any more from this plant for the rest of the year and remember not to force it two years in a row.
- March: Plant new rhubarb crowns out in the open ground.
- Crop your plants regularly, always leaving some leaves on so that it can feed itself.
- Allow leaves to die down, then clear away.
- Mulch around the crowns with well-rotted compost.
- Select one or two rhubarb plants for forcing and enjoy rhubarb in mid-winter.
pests, diseases & common issues
rhubarb crown rot
Rhubarb crown rot can be caused by either bacterial or fungal infection and is exacerbated by waterlogged soil and poor air circulation. Ensure when mulching that you do not cover the crown. If you do notice the whole crown beginning to rot it is best to destroy the plant and start again with a new crown in a better drained spot.
red leaf disease
If red spots start to appear on the leaves this is a sign of a fungal infection that will rarely kill the plant. It is best to remove affected leaves and not add them to the compost. Ensure good air circulation and do not mulch too close to the crown.
why is my rhubarb not growing well?
If the stalks start to get weak and spindly on an established plant this is usually a sign that it needs lifting and dividing. The central section has probably become old and woody and should be discarded, whilst the younger rhizomes around the edge can be replanted in a new spot with well composted organic matter.
why is my rhubarb growing flowers?
This is usually a sign of stress, either from lack of food or water – the plant is determined to propagate itself before it disappears. Some guidance says it is due to too much fertiliser and water – so basically you can’t win! The reassuring thing is that it rarely harms the plant, it might just reduce your crop for the year. Remove the flowering shoot, or alternatively enjoy their exuberance for a week or so, cutting down before they have the satisfaction of setting seed. Growing more than one variety ensures that you will get a decent crop whatever happens.
what is killing my rhubarb?
It is unlikely to be a pest, as very few animals or insects will eat the leaves. Slugs and snails might have a go at tender forced shoots, especially in the shelter of a cosy forcer, so keep an eye open for those. It is more likely to be a fungal infection, caused by waterlogging, or alternatively lack of moisture caused by growing on too sandy a soil.
frequently asked questions
how far apart should you plant rhubarb?
You will need to allow at least a metre between plants as their stems and leaves will soon spread to fill the space.
how deep to plant rhubarb?
The dormant crown wants to be just below the surface of the soil. If growth has already started in the pot, plant at the same level in the ground.
when is the best time to move or divide a rhubarb plant?
Whilst the plant is dormant, so any time between November and March. In autumn the soil you plant into will still be warm, allowing for good root development. If you wait until early spring the plant will be raring to go, so that shoots develop quickly, meaning they will require more moisture.
how often should you water rhubarb?
If you are growing it in the open ground it will only need watering when first getting established, or during prolonged dry periods. If in a pot, you will need to give it a good drink every week whilst it is in leaf.
should you cut or pull rhubarb?
You should always try to pull the stems, this avoids leaving any cut stubs to die back and possibly introduce fungal disease.
when to stop picking rhubarb?
This depends on the variety. If it is an early type that you have been picking since the spring, then stop around June so that the plant can replenish itself for next year. Later varieties can be picked until August, after which the stems tend to get a bit woody and tough. Some people worry about the build-up of oxalic acid over the summer, but this is concentrated in the leaves, rather than the stems, so is rarely a problem.
is rhubarb poisonous?
The leaves of rhubarb contain oxalic acid which can be poisonous in high doses. It also tastes awful, which is why we cook and eat the stems, rather than the leaves.