ROSE blackspot: This disease is responsible for the unsightly black or purplish spots that appear on many roses from spring onwards, later turning yellow and leading to early leaf fall.

A bad attack of blackspot can virtually defoliate roses, which looks awful and inevitably weakens the plant, although it is rarely fatal.

Blackspot is caused by a fungus that overwinters as spores on shoots, on fallen leaves and on the surface of the soil. Your normal winter or spring pruning will remove a lot of these spores, and there are also useful steps you can take now to reduce the occurrence of the disease next year. Rake up all affected leaves, and remove any still on the plant.

You can compost these if you're going to use the resulting material elsewhere in the garden.

Otherwise, consign them to a communal compost collection or, as a last resort, burn them. Covering the soil with mulch will suppress weeds and retain moisture, but also stops blackspot spores being splashed up onto the plant to re-infect the new leaves in spring. If you want to take further preventative treatment, then apply green sulphur, which is acceptable to organic gardeners, or a fungicide containing mancozeb when the foliage opens in spring, and at intervals through the summer. When buying new roses look out for resistant varieties such as pink Silver Jubilee, yellow/scarlet Tequila Sunrise, deep orange Fellowship and rich crimson Deep Secret.

Good climbers include white Mme Alfred Carriere, pink Compassion, yellow Golden Showers and deep red Dublin Bay.

Jobs of the week:

l Plant lily bulbs and tulips

l Take root cuttings of perennials with thick, fleshy roots such as acanthus, dicentra, oriental poppy, sea holly and verbascum

l Move patio containers to a sunny, sheltered spot and raise on pot feet or bricks so they can drain freely

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