RocketEruca vesicaria subsp. sativa

Rocket is accommodating: full sun in March-April and September to grow fast, partial shade from June to August so it does not run to flower or become too hot. Give it the edges of beds, the gaps between tomatoes or cabbages, the square freed by radishes or peas. Ordinary, moist, loose soil is enough; it even tolerates poor soils, where its leaves are more fragrant. As it is a brassica, do not sow it on a bed where cabbages grew the year before, and avoid following it with cabbages: flea beetles and clubroot would be delighted.

A simple scratching over to ten centimetres is enough, followed by a fine raking. Rocket has no need of fresh compost; a handful of mature compost per square metre, worked into the surface, is ample, and soil too rich in nitrogen produces soft, bland leaves. Remove stones and roots, firm lightly with the rake. On our loams that crust over, a sprinkling of potting compost or sieved compost over the drill helps germination. Moist soil matters more than rich soil: it is drought, not poverty, that makes rocket bitter.

Sow from mid-March, under fleece the first few times, until the end of September, in short rows of one or two metres every twenty days. Draw drills one centimetre deep and twenty centimetres apart, sow thinly, one seed every two centimetres, cover with fine soil, firm and water with a spray. Germination takes four to eight days from 10 °C. A broadcast sowing over one square metre, at one gram, gives a carpet to harvest with scissors. In July, sow in partial shade and in the evening; in September, go back to the sun for a harvest until the frosts.

Two plants hide behind this name. Cultivated rocket, Eruca sativa, has broad, mild leaves and a fast cycle: thirty days from sowing to the first cut, then it runs to flower and must be resown. Wild rocket, Diplotaxis tenuifolia, has fine, cut leaves, a more peppery taste, and is a perennial: a single spring sowing produces for three years, coming back every year, and stands up to frost. To start with, sow both, the cultivated one for speed, the wild one as a permanent edging. The wild one germinates more slowly, two weeks, and asks for a finer tilth.

Rocket is sown in place: its taproot dislikes transplanting and its rapid growth makes it pointless. Thin to five centimetres for a harvest of young leaves, to ten for plants that will give three or four cuts, and eat the seedlings you remove. If you buy a pot from a garden centre or rescue self-sown plants from a plant that went to seed, transplant with the whole root ball, without touching the roots, and water at once: establishment is fine in spring and autumn, poor in summer.

Rocket is one of the most rewarding balcony crops. A window box fifteen centimetres deep and fifty centimetres long, filled with ordinary potting compost, is enough for a broadcast sowing, thinned to five centimetres, that gives leaves in a month. Place it in the morning sun and in afternoon shade in summer, in full sun in spring and autumn. Water every two days, every day in hot weather; the compost must not dry out. Sow a new window box every three weeks so as never to run short, and bring one indoors behind a cool window in winter.

Sowing the whole bed at once gives a wall of white flowers three weeks later and nothing to eat. Sowing in July in full sun on dry soil produces tiny, scorching leaves. Letting flea beetles riddle the seedlings from emergence, with no fleece or watering, has discouraged many a gardener. Burying the seed two centimetres deep delays germination. Finally, waiting for the leaves to grow large before picking is a mistake of taste: rocket is eaten young, at eight centimetres, while it is still mild and crunchy.

Thirsty rocket turns bitter and tough and bolts. Water as soon as the surface dries, twice a week in spring, every two days in summer, in the morning, with a fine spray, three to five litres per square metre. Regular watering is also the best weapon against flea beetles, which hate moisture. In autumn, rain is enough. Never let a sowing germinate and then dry out: five-day-old seedlings have no reserves. Under fleece, check the moisture by slipping a finger into the soil; the fleece holds water in but does not supply it.

A very thin mulch of hemp, flax or dried grass clippings, one centimetre at most, laid after thinning, keeps the soil cool and stops soil splashing onto the leaves. Do not mulch sowings; rocket germinates in light and mulch shelters slugs. No fertiliser is useful: over-fed rocket loses its flavour and fills up with nitrates. If a late-summer sowing stalls in exhausted soil, a single watering of nettle liquid diluted to 5 % is enough to restart it. Hoe lightly between the rows until the mulch is laid.

Thin as soon as the seedlings have two true leaves, to five and then ten centimetres, to get broad leaves and airy foliage. As soon as a flower stem rises in the centre, pinch it out with a fingernail: the plant produces another two or three weeks of leaves, smaller and more peppery. Beyond that stage, let one or two plants flower; the cream flowers are delicious in salad and the seed, gathered in dry pods in August, self-sows or keeps for three years. Pull up the other bolted plants and resow in the space freed.

Flea beetles, small jumping black beetles, riddle the leaves with round holes from April, especially in hot, dry weather. Lay fine insect-proof mesh from sowing, keep the soil moist, mulch and hoe in the morning, when they are sluggish. A sowing in partial shade is less attacked. Slugs target the seedlings: trap planks, evening hunts, ash in dry weather. The cabbage white sometimes lays on rocket in summer: pick the caterpillars off by hand. A strict rotation, with no brassicas two years running, keeps clubroot at bay, as it strikes rocket too.

In March, sow under fleece, a first time. In April-May, sow every three weeks in the sun, thin, lay mesh against flea beetles, water. In June, pinch out flowers, sow in partial shade. In July-August, sow in the evening in the shade, water every two days, let one plant go to seed. In September, sow twice in full sun for autumn, remove the covers when the nights turn cool. In October-November, harvest, cover with overwintering fleece when frost is forecast. In December-February, pick the wild rocket that holds up in the cold and prepare the March sowings.

Cut the outer leaves with scissors two centimetres above the neck as soon as they are eight to ten centimetres long, a month after sowing, leaving the heart to grow: three or four cuts are possible a week apart. On a broadcast sowing, shear by patches, at three centimetres. Pick in the morning, before the heat, for a balanced flavour. To extend the season, a fleece in March and October gains a month at each end, a cold frame allows harvesting all winter, and wild rocket, perennial and hardy, provides without interruption from March to December from a single sowing.