Salad crops, such as lettuce, rocket, radish, and scallion, should be sown, a little at a time every few weeks, to ensure a constant supply. Sow the seed in modules or very thinly in small seed trays and transplant into the open garden when the plants are a couple of weeks old. If you have a slug-free patch, you can sow directly into the soil, thinning out the plants as they appear. Rocket is very swift to flower, after which the leaves become coarse and overly-sharp. The plants will last longer if you snip the tall flowering stems almost back to ground-level as soon as the hairy, rice-grain-size flower buds appear. New leaves, and flowering stems (which, in time, may be cut back like the first lot) will appear from the base of the plant. At the end of the season, leave one plant to flower and set seed. You can collect the seed pods when they have dried and store them for next year's crop.