Site and soil | Varieties | Sowing and propagation | Planting | Aftercare | Picking | Blanching and Forcing | Pests and Diseases
A vegetable that is eaten like a fruit, usually with added sugar to temper its acidity, rhubarb is making a return to popularity with contemporary chefs who appreciate its clean, tart flavour. If you are planning to grow rhubarb, now is the time to plant, or if you already have plants, you could consider starting to force some this month for early supplies this spring.
Site and soil
Rhubarb needs rich fertile soil, well-drained and well supplied with organic material. Although that is the ideal, it grows well in almost any soil that is not water-logged or very dry in summer. Water-logging causes the thick fleshy roots to rot and very dry conditions cause the plant to wilt in hot weather and grow very poorly. The other major requirement is full sunshine. Rhubarb does very badly in shade. Quite often, because it remains so long in the ground, the branches of neighbouring trees grow out over the spot where the rhubarb is growing and the roots invade their root space. The combination of overhead shading and root competition can greatly weaken the rhubarb and even kill it.
There are lots of varieties of rhubarb but very few of them are widely grown. The crop was very popular in the nineteenth century and many varieties were named then, some of them are still around. The plant is a hybrid of two or more species and has been grown for thousands of years in China where its roots were used as a powerful laxative. It was first brought to Europe as a medicinal plant. The practice of eating the leaf stalks began in France but was quickly taken up across Europe. The main variety used is ‘Timperley Early', an early-sprouting variety with red stalks and green flesh. Other varieties offered include ‘Victoria' and an early form called ‘Early Victoria'. A batch of varieties carrying the names ‘Champagne', ‘Hawke's Champagne' or ‘Red Champagne' are similar with red stems and a flavour described as ‘winey'.
Sowing and propagation
Rhubarb can be raised from seeds, which is erratically offered by seed companies, or from collected seeds. Most plants flower and set some seeds and these can be gathered and sown fresh. The resulting plants are unlikely to be much better than the parent and the easier way to propagate plants is to split an existing plant, or ‘stool'. Any piece of the crown that carries a bud will give rise to a new plant, but it is best to have two or three buds on a piece for planting as it will give a crop sooner.
Planting is normally done when the plant is dormant in winter, or in growth from pots. The ground for rhubarb should be dug over incorporating some well-rotted manure or compost. Make sure to remove all perennial weeds and ensure there is enough space for the plants to grow. Each stool needs about 1.5 metres from the next or from other plants such as fruit bushes. The usual recommendation of 90 centimetres or one metre is too close. When planting dig out a wide hole to 60 centimetres or more and fill the bottom of the hole with well-rotted organic material and mix it with the soil. Then plant on the slightly raised mound. Water after planting, even in winter, to settle the soil around the roots. One or two plants is usually enough for most households and a single plant can be planted in a flower border if necessary.
Rhubarb needs very little effort to maintain. Weed control must be kept up although it suppresses weeds well when the leaves are present. Feeding can be carried out in winter with a thick layer of organic material, farm yard manure was the traditional dressing applied. A layer of grass mowings, applied fresh in summer, acts to keep weeds down, retains moisture in the soil and rots down to feed the plants. Water can be given during drought spells but the plants will usually stop growing in any case and the main season for using rhubarb will have passed.
Usually the plants are given a year to establish before picking the first leaves. In subsequent years, the leaf stalks can be picked when they are as small as pencil length, early in the season. Later they will grow out to full size. The method of picking is to hold the leaf stalk firmly down near the base and with a firm tug pull the leaf out of the crown. Cut the leaves off and leave them on the soil surface near the plants or on the compost heap.
Blanching and forcing
Rhubarb can be blanched to produce stalks with red colour. This is done by covering with any light-excluding material, traditionally a layer of straw, or a large pot or container, and special rhubarb pots are available. These are decorative in themselves, especially at time of year when the vegetable garden is bare. The pots can be placed over the plants in late December or early January when they have had some frost.
Forcing the plants in a greenhouse or indoors can bring early supplies of bright red stems. The crown, or part of a large crown, is lifted and placed in a black plastic bag, which can be used for rubbish subsequently, and brought into a relatively warm place. Growth begins quite quickly and in a couple of months long stems are produced. The forced crowns are usually discarded but they will recover if planted outdoors.
Pests and diseases
Rhubarb is resistant to most pests, containing high amounts of poisonous oxalate in the leaves. It can be affected by honey fungus and verticillium wilt. When affected by these diseases, the crowns grow poorly and wilt easily. Crown rotting can occur when the ground is heavy and wet.