What to do in the garden this week

Growing basil Aromatic basil is an essential summer herb that’s best started off under glass or close to the kitchen on a light windowsill. Sow two or three seeds in a 3in pot in free-draining compost (see below). Successional sowings every week or two will provide a continuous supply.

* Spring cabbage

July and August are good for sowing next year’s crop of spring cabbages; although it may seem very early, you’ll be glad to have the results during the leaner times of spring. Sow in plug trays under glass. Once big enough, it’s an advantage to pot on, giving you a stronger plant, as ground conditions may not be so kind in the height of summer. If you’re short of space, plant a few where you’ve taken up your second early potatoes; the cabbages will cover the ground during winter and use up the potatoes’ remaining nitrogen.

* Potting composts

Peat-free potting composts are often made from composted bark, but, like peat, they’re light in weight and shrink when dried, making watering difficult. Instead, look out for the traditional John Innes soil-based potting composts, which are well aerated and hold nutrients effectively. The John Innes mix is heavy, so it gives stability to the containers and is more forgiving if it gets too dry.

* Salad-leaf mixtures

Mixed salad leaves are enjoying huge popularity and are easy to grow, ideal for a container near the kitchen door and for filling gaps in the kitchen-garden beds. Unlike a head of lettuce that matures before use, salad-leaf mixtures are treated as cut-and-come-again, by snipping out leaves here and there. Sow thinly and use when the leaves are large enough to pick.

* Herbaceous flowers

The ambition of most plants is to reproduce themselves, and they usually do this by setting seed. Then they’ve done their job and stop flowering. If you remove the spent blossoms, you can force some plants to flower more strongly and for longer than if they’re left to set seed. Annuals, such as marigolds, petunias, salvias and sweet peas will all benefit from dead-heading, as will tender perennials such as penstemon, osteospermum and dwarf scabious; the latter group will also look better for a good tidy-up. I prefer to leave the flowers in our herbaceous borders alone, as cutting off the flowering stems can leave gaps for the rest of the year, thereby upsetting the balance of the architecture.

* Caterpillars

Whether from the butterfly or the sawfly family, caterpillars are a menace and will devastate your plants if you’re not extremely watchful. Sawfly caterpillars will defoliate Solomon’s Seal early in the season; the gooseberry sawfly devours the leaves so that your fruit is growing on bare branches; the cabbage white caterpillar will destroy your brassicas. As there are no benevolent organic controls readily available, keep an eye on vulnerable plants and squash the pests when young. Spraying isn’t recommended as it also harms more helpful insects.