Rocket

Light and exposure

In spring and autumn, rocket enjoys full sun or bright light. In these seasons the heat stays moderate and the plant grows fast and thick without trying to flower. A well-exposed bed gives it full, well-coloured leaves.

In high summer, change your strategy: look for partial shade. A spot shaded during the hottest hours, at the foot of a taller crop or against a hedge positioned to cut the scorching sun, clearly delays bolting. The direct heat of high summer is its worst enemy, partial shade is the best way to keep it tender.

Watering

Rocket wants soil that stays cool at all times. This is even the key to keeping it mild: a plant that goes thirsty turns tough, fibrous and far more pungent, and it heads straight for flowering. Water regularly, without soaking, aiming at the base rather than the foliage.

In summer, watering becomes daily in dry, hot weather. The slightest touch of drought triggers bolting and spoils the harvest. A light mulch around the plants helps hold moisture and space out watering. In the cool seasons, and in a damp climate, rain is usually enough.

Soil and repotting

Ordinary soil, cool and well loosened at the surface, suits rocket very well. It is not demanding and grows in almost any garden soil, as long as it holds a little moisture. An addition of mature compost before sowing supports rapid growth and tender leaves.

Avoid soils that dry out too quickly, sandy and exposed, because they speed up bolting in summer. Soil that keeps cool, mulched if possible, is the best asset for prolonging harvests during the warm season. In a pot or window box, choose a deep enough container and keep a close eye on the watering.

Temperature and humidity

Rocket is a cool-season plant. It germinates and grows best between 10 and 18 degrees, which matches the shoulder seasons of temperate climates. Within that range it stays tender, mild and productive for several weeks.

Beyond 20 degrees everything gets complicated: the plant bolts to flower very fast, the leaves turn small, leathery and burning in the mouth. It withstands cold far better than heat and takes light autumn frosts without trouble. It is therefore not winter that stops it, but rather the heatwave.

Pruning and upkeep

Rocket is not pruned, it is harvested by cutting, and that is exactly what makes it so practical. Take the young leaves with scissors or a knife, a few centimetres from the soil, leaving the heart intact. The plant starts again and gives a fresh wave of leaves, often two or three harvests from a single sowing.

As soon as flower stems appear, cut them if you want to delay the plant’s end a little. But once bolting is well under way, it is better to pull it up and sow again elsewhere. You can also let it flower: the white veined flowers are edible, pretty and attract pollinators.

Pests and diseases

Rocket’s number one enemy is the flea beetle. These tiny jumping beetles riddle the leaves with small round holes, especially in hot dry weather on young plants. The best defence is an insect-proof net laid at sowing, which stops the flea beetles from reaching the leaves. Keeping the soil cool with regular watering also discourages them, as they prefer dry conditions.

Like all Brassicaceae, rocket can attract the caterpillars of the large white butterfly and, on heavy, damp soil, suffer from clubroot. Crop rotation, avoiding putting it back where cabbages, radishes or turnips have grown, limits this risk. Slugs also attack young seedlings in autumn, as with most salads.

Propagation

Rocket is propagated by direct sowing in place, very simple and very fast. Sow in rows or broadcast, under a few millimetres of fine soil, then firm down and keep cool. Emergence is express, often three to seven days, and the first leaves are cut four to six weeks later. Sow a little each time but often: this is the principle of successional sowing, which ensures a continuous harvest.

For your own seed, let a few plants run to flower, then form their pods. Rocket also self-seeds easily on its own if you let it. Harvest the pods when they dry and turn brown, before they burst, then extract and keep the seeds dry. They stay viable for several years.

Month-by-month care calendar

Green Hub tips

• Sow in succession: a short row every two to three weeks gives young rocket continuously, rather than a mass that bolts all at once.
• In summer, look for partial shade and water without fail: it is drought and heat, not cold, that make it run to seed.
• Lay an insect-proof net from sowing. Flea beetles are the main enemy and riddle the leaves with small round holes in a few days.
• Harvest by cutting and leaving the heart intact: rocket grows back and gives two or three waves of leaves from a single sowing.