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This weekend’s gardening jobs: warm soils make it the perfect time for planting courgettes and seedlings

A close up of courgette plants being watered in a growbag. Photo: RHS

A close up of courgette plants being watered in a growbag. Photo: RHS

As plants grow, some trimming can be helpful, while others can be propagated by the simple technique of layering. Those young shoots might need protection from aphids, however. The warming soils allow tender courgettes to be sown and it is peak season for planting. Any fertile soil will produce enormous crops – three courgette plants is enough to feed most families.

Trimming perennials

Judicious shortening now by about half leads to compact plants less prone to flop, and usefully delays flowering. Aster, helenium and sedum are suitable. Alternatively, remove one in three stems – severed stems re-grow and flower later, prolonging the display. Even after flower buds appear in late spring, there is scope for trimming all the stems by degrees, generally by a third, resulting in a bushier plant and longer flowering season. Echinacea (right), monarda and rudbeckia respond well to this.

Courgettes

These can now be sown outdoors (below) or indoors in cell trays, and grow quickly. If outdoors, cover the seedbed with fleece or cloches to deter the bean seed fly that can damage them. Any fertile soil in reasonable sun will produce enormous crops – three plants is enough for most families. Allow 90cm between plants. For something unusual, consider climbing courgettes trained up bean poles. They crop abundantly, suit small gardens, are tasty and look pretty. Try “Black Forest” with its dark fruits and yellow “Shooting Star”.

Greenfly and blackfly

Aphids multiply exceedingly in late spring. By midsummer, natural enemies and diseases usually suppress them, but they can be damaging in the meantime. If spotted early, they can be wiped off. However, once their colonies are numerous and plant growth is distorted, an insecticide is usually required. Ones based on fatty acids – that is, soaps or oils – kill aphids, but if applied at dusk do little harm to bees, ladybirds and other useful insects.

Echinacea Sombrero Baja Burgundy 'Balsombabur'. Photo: RHS

Echinacea Sombrero Baja Burgundy ‘Balsombabur’. Photo: RHS

Planting out

Home-grown and bought plants go out now. Good planting avoids losses and gets good results. Water is key – soak dry soil the previous day and water the plants thoroughly before planting. Fertiliser is less important, but using liquid fertiliser during the pre-planting watering is good practice. With your trowel, make a suitable-sized hole, place the plant in it and fill with water. When it has drained, firm the plant, ensuring the rootball is only barely covered with soil.

Layering

Bending a suitable low-growing shoot to soil level, pinning it in place with a “U”-shaped wire “staple” and covering with a low mound of soil induces roots to form on a wide range of plants by autumn: acer, camellia, cornus, cotinus, lilac, rhododendron and of course climbers including clematis, grape vines, jasminium and wisteria. A useful extra is to slightly wound, with a knife or a light “twist”, the lowest part of the bent stem to enhance rooting.

Twitter: @GuyBarter

Guy Barter is the chief horticultural adviser for the Royal Horticultural Society

The Royal Horticultural Society is a charity working to share the best in gardening and make the UK a greener place. Find out more at rhs.org.uk

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