Grower’s Corner – rhubarb
While people are either rhubarb lovers or rhubarb haters, there’s no doubt that this is one of the best fruits to grow on the allotment: it’s a hardy, frost-resistant vegetable which actually benefits from a period of frost in the winter in order to produce the best flavoured stalks.
Soil preparation is vital and all varieties of rhubarb develop a deep root system and grow best in a fertile, free-draining soil. This means the very minimum that you need to do is dig over your chosen location a month before planting, removing any stones you find and adding as much organic matter as possible. It’s preferable to do this a season before and again a month before if you can.
It’s best to buy one-year-old plants, known as ‘crowns,’ that have been divided from strong, disease-free plants. While rhubarb can be grown from seed, it’s not easy to germinate and it won’t necessarily come true to type. Plant your crowns in late autumn to early winter. You need to choose your variety with some care, as many varieties grow to be very large plants, and require massive space. Plant to a depth that means the top of the plant is at, or just below the soil surface and place the crown in the hole with its roots facing downwards. Mark where the crown has been planted with a cane or stones until new shoots appear above the soil surface in late February or March. Gently firm the surrounding soil and water well. Spacing between plants should be about a minimum of a foot for smaller varieties, and up to four feet for larger varieties.
Allow rhubarb to establish for a full year before taking your first harvest and then take the three largest stalks, waiting for the leaves to fully open before pulling (depending on variety, this may be any time from May to August). Stalks are harvested by gently twisting the stems and pulling from the base of the plant. Note that leaves should not be eaten, as they contain oxalic acid and are poisonous, but they are fine to compost, although there is a myth that you shouldn’t!
Forcing This is the process that provides an earlier harvest of sweeter stems – often they wont even need peeling. For forcing outdoors, simply cover plants with a container or large pot to exclude the light. Place the cover over the rhubarb as soon as it begins to show signs of growth in spring.
Problems and diseases This fruit suffers from few diseases. Crown rot is the main threat, particularly if soil conditions are wet. The fungal infection occurs at the base of the stalks where crowns turn brown and soften and plants suffering from rot should be dug up and destroyed immediately. To avoid crown rot, make sure rhubarb is planted in fertile, well-drained, weed-free soil and if you are forcing, lift the pot from time to time to check there is no water-logging happening underneath as water can be trapped in the pot. Dead-head flowers immediately after they appear in the early spring, as allowing flowers to set seed will weaken the plant.
Aftercare After non-harvested leaves have died down, spread a new layer of compost around the plant to conserve water and suppress weeds. Rhubarb should be divided every five or six years during winter, when dormant to keep them productive. Each plant can be split into three or four separate crowns with a spade. Make sure each crown has an ‘eye,’ or large bud that will provide next year’s shoots.
Rhubarb photographs by kyz and Rochelle et al, used under a creative commons attribution licence