When to sow rocket

Sow rocket outdoors from April to early September. Rocket is a long-day plant: as the days lengthen towards midsummer, and even more in heat and dry soil, it flowers quickly and the leaves turn hot and bitter. Spring and late-summer sowings give the longest, mildest harvests.

Salad rocket only crops for a month or two before it flowers, so sow a short row every few weeks rather than one long one.

For the earliest leaves, sow under cover in February and March. Sowings in August and September in a greenhouse, cold frame or under a cloche give leaves through autumn and into winter; outdoors, a cloche or fleece extends the season by about a month.

Sow thinly in drills no more than 0.4 in deep, with rows 6 in apart. Wild rocket has tiny seed; sow it as shallowly as you can, around 0.2 in.

Thin seedlings to about 6 in apart, or leave them closer and cut them young as a baby-leaf crop.

A 120 × 80 cm raised bed takes five rows 6 in apart with a plant every 6 in, about 40 plants. In practice most gardeners sow one or two rows at a time and follow up a few weeks later.

Rocket grows in pots too: use one at least 12 in wide.

Salad rocket likes fertile soil that holds some moisture. Keep it well watered: dry soil is the quickest way to make it bolt and go fiery.

In spring and late summer give it full sun. For sowings in early and midsummer, choose a cooler spot with light shade to keep it cropping longer.

Go easy with fertiliser. Like spinach, rocket can build up high nitrate levels when it is given too much nitrogen.

Start picking four to six weeks after sowing. Treat it as cut-and-come-again: take a few leaves from each plant, or cut the row a few centimetres above the soil and let it regrow.

Once flower stalks appear, the leaves quickly turn bitter, and it is time to sow the next row.

Salad rocket (Eruca vesicaria subsp. sativa) is an annual with bigger, softer, rounded leaves and a milder taste. It grows fast, but crops for only a month or two before it flowers.

Wild rocket (Diplotaxis tenuifolia) is a perennial with narrow, deeply cut leaves and a stronger, more peppery flavour. It is slower to get going, copes with poorer, drier soil, and keeps producing over a longer period, even after flowering. Most bagged rocket in shops is wild rocket.

Flea beetles are rocket's typical pest: tiny jumping beetles that pepper the leaves with small round holes. The damage is mostly cosmetic on established plants, but it can set back seedlings. Fine insect mesh over the row from sowing keeps them off.

Slugs and snails go for seedlings and young plants. Downy mildew and white rust can appear in damp weather.

Rocket belongs to the cabbage family (crucifers) and can carry the same soil problems, including clubroot. Rotate it together with cabbages, radishes and other crucifers rather than using it as a filler in every free gap of the brassica bed.

Because it is small and quick, rocket slips easily between slower crops or into gaps after an early harvest. Planting tables also recommend it next to lettuce, beans or carrots; we found no evidence for these pairings beyond sensible use of space.

The rule with a real reason is rotation: count rocket as a crucifer and keep it with the cabbage family.