Rhubarb is an attractive hardy perennial with large leaves and pink, red or greenish leaf stalks that are used as a dessert, often in pies and crumbles. Stems are usually picked in spring, but plants can be covered with pots to produce an early crop of blanched stalks in late winter. The flavour of rhubarb varies in sweetness depending on the age of the stems. Rhubarb is extremely easy to grow, and plants crop well for many years.
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You can sow seed in March or April either indoors or in the ground. Prepare your sowing site by weeding then raking to a fine texture. Sow seeds 2.5cm (1in) deep, then thin out the seedlings to 15cm (6in) apart, choosing the most vigorous plants. Protect seedlings and young plants from slugs and snails.
If sowing indoors, use small pots or modules filled with seed compost. Water well, and continue watering and potting on as they grow. Transplant the young rhubarb plants into their final position in autumn or the following spring (see planting details above).
Water during prolonged dry periods in summer. Growth will slow down and even stop if conditions are too hot and dry. Plants in containers need regular watering throughout the growing season, as they dry out much more readily. To boost growth, apply a general fertiliser in spring or summer.
Every spring, apply a mulch of well-rotted garden compost in a layer about 7cm (2½in) deep around rhubarb plants, but take care not to bury the crown. Mulching helps to retain moisture in the soil.
Allow the foliage to die back naturally in autumn, then cut away the old leaves to expose the growing points to winter cold. There is no harm in adding these leaves to the compost heap, as the poisonous oxalic acid contained in them breaks down during decomposition.
Rhubarb requires seven to nine weeks of cold weather below 3°C (37°F), depending on the cultivar.
Dividing large plants
It’s best to divide established clumps of rhubarb every five years or so, especially if they have become overcrowded or growth is weak. This will also give you vigorous new plants for your own garden or to share with friends. The resulting plants are exact clones of the parent.
Lift the dormant crown between autumn and early spring – ideally in November. Use a spade to divide the crown into several smaller sections, each with a portion of the rhizome (thickened root) and at least one growing point or bud. Sections from the outer part are better than the centre of old plants. Discard any old or decayed parts of the crown. Replant straight away or wrap in damp sacking until ready to plant.
Remove flower stalks
Remove the whole flower stalk as soon as it appears, to prevent it weakening the plant. Some cultivars are more prone to flowering than others, and it is more common after a wet summer or if a high nitrogen feed has been overused.
Rhubarb needs an open, sunny site with moist, but free-draining soil, as it dislikes being waterlogged in winter. Avoid planting in sites that are particularly prone to late frosts, as the young stems may be damaged.
Rhubarb can be grown from seed, but it’s more common to plant dormant crowns between autumn and spring. You can also buy plants in pots in active growth – these can be planted at any time of year, but it's best to avoid planting in hot dry weather.
Prepare the planting site by digging in two bucketfuls of well-rotted manure per square metre/yard. Then dig a planting hole and position the plant so the tip of the crown is just visible above the soil. If planting more than one, space them 75–90cm (30–36in) apart.
Rhubarb can also be planted in very large pots, at least 50cm (20in) deep and wide.
Crown rot: This is a common problem caused by various soil- or water-borne fungi or bacteria. Plants look sickly, fail to grow and rot at the crown. This can spread to the stems and leaves, causing the plant die.
Remedy: Prompt action may save the plant. Remove affected areas by cutting well back into healthy tissue.
Slugs and snails
These feed on the young seedlings and you'll see the tell tale slime trail on the soil around your crop, as well as on the leaves.
There are many ways to control slugs and snails, including beer traps, sawdust or eggshell barriers, copper tape and biocontrols.
With newly planted rhubarb, resist the temptation to harvest any stems in the first year, as this will reduce the plant’s vigour. The following year, pick just a few stems. After that, the plant should be well established and can be harvested normally.
On established plants, stalks can be picked from March or April onwards for early cultivars, and late April or May onwards for maincrop varieties. Although the stems remain edible and tasty through summer, it’s best to stop harvesting by June, or at least only take a few stalks after then, so you don’t over-harvest and weaken the plant.
To harvest, hold the stalk at the base and ease it out of the ground – try to avoid snapping it off.
Only ever take about a third of the plant's stems, so there are plenty left to keep it in active growth.
Earlier harvests of sweeter, tender, pale stems can be produced by covering rhubarb plants with a forcing jar or bin in late winter, so the stalks form in the dark. They can be ready to harvest as early as March, several weeks before plants left to grow normally.
Nigel Slater's roast rhubarb, which is allowed to brown slightly, creates a delicious mixture of sweet and tart. Best served with vanilla ice cream or frozen yoghurt.
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