Rhubarb pick of the crop

Early rhubarb is prized by chefs, says Kitty Scully and growing the ‘hungry gap’ plant is easy from crowns.

For a novice vegetable and fruit grower, rhubarb is one of the easiest crops to start with. It is practically disease free, (bar the fungal disease crown rot which thrives in wet conditions), and will flourish without too much attention providing tasty stalks at a time of year when stored apples have gone over and little else is ready for harvest in the garden.

Grown for its delicious pink stems, rhubarb is a very hardy, frost-resistant plant that can tolerate partial shade and actually requires a period of frost in the winter in order to produce the best stalks. Rhubarb does best when planted in late autumn or early winter and can be grown from seed, but this is rather uncommon and the best option is to buy and plant one-year-old ‘crowns’ that have been divided from strong, disease-free plants.

DIVIDING RHUBARB

In order to maintain healthy harvests, plants should be divided every five or six years during winter when rhubarb is dormant. Use a spade to split each plant into three or four separate crowns with a spade. Ensure that each crown maintains an ‘eye’ or a large bud as these are essential for providing next year’s shoots. Plant divided crowns into a hole slightly larger than the divided plants and place the crown in the hole with roots facing downwards. The top of the crown should be approximately 2.5cm below the soil surface. It can be useful to mark where the crown has been planted with a cane until new shoots appear in late February or March. Do not harvest stems in the first year as this will affect plant vigour in future years.

FORCING

Growing plants in the dark, often with the addition of a little warmth, is known as ‘forcing’ — a simple way of tricking nature into early growth with results that are simply sublime.

Rhubarb responds very well to forcing and even though all homegrown rhubarb is delicious, it is those stems grown in darkness that are the most desirable of all. Forcing is somewhat akin to blanching and other crops such as celery, sea kale and cardoons also respond well to this growing technique.

Rhubarb naturally breaks its overwintering buds in early spring, as soon as temperatures are consistently mild. The stems (also known as rhubarb ‘sticks’) can be harvested as soon as they are big enough, from mid spring right up to the middle of summer, when the plants should then be left to recharge for the remainder of the growing season.

Forced stems however can be enjoyed a whole month sooner. Forcing rhubarb creates etiolated stems (botanical speak for stems that are pale and drawn out due to lack of light).

The simple science involves the inhibition of photosynthesis due to lack of light, a process that encourages plants to desperately seek light and synthesise less light in. This results in pale, smooth, long thin rhubarb sticks which chefs go mad for.

Why? For the cook, these stretched tender pale stems are sweeter than non-forced rhubarb and do not contain the familiar rhubarb ‘strings’. The pale stems also require less sugar to balance their tartness thus providing a taste and colour that is deliciously delicate.

HOW TO FORCE

The easiest way to force rhubarb is to do it in situ, without disturbing the crown, while the plants are still dormant in late winter. Forcing can be done between November and February. The object is to cover promising buds so that light is completely obstructed. Clear around the base of the rhubarb crown, removing old leaves and weeds. Traditionally decorative purpose-made bell-shaped terracotta forcing pots were used. These can be hard to find and expensive to buy so improvise by using whatever pot you have to hand. Old black dustbins work very well but if they have any holes, make sure to plug or cover with tape to prevent the slightest chink of light from reaching the buds. Most years, forced rhubarb will be ready to harvest eight weeks after covering. Some gardeners like to pack manure or straw directly around the buds inside the pot to create a warm microclimate and speed up the process.

All rhubarb can be forced, but some varieties respond better than others such as ‘Timperley Early’ whose name even suggests its willingness to grow early in the season.

Be informed that forcing rhubarb is not a natural process. It does provide harvests earlier but it is more demanding on plants. Crowns that have been forced should be left to recover the following year to avoid weakening the plant and making it susceptible to disease. For this reason it’s best to have two or more plants on the go so that forcing can be alternated from year to year.