Top-dress blackberries with 100g per square metre of general-purpose fertiliser in mid-spring and cover with a 7cm (3in) organic mulch annually. Make sure the mulch is placed 5cm (2in) away from the new canes and the crown to prevent rotting.
Water young plants every 7-10 days during dry spells. While mature plants shouldn’t need extra watering, their fruit size will benefit from watering every 10-14 days if the summer is particularly dry.
Pruning and training
Blackberries are vigorous and need regular pruning and training. Regularly tie in the shoots of newly-planted canes. Once these reach their first winter, cut back all sideshoots produced on these main canes to 5cm (2in). It is mainly from the resulting fruiting spurs that flowers are formed.
In the second year after planting the crown will throw up new canes from ground level. Loosely bundle these together; insert four bamboo canes in a square vertically around the crown and pull the new canes into the centre; then tie some sturdy twine around the square to hold the new canes in place.
Remove the one-year-old canes once they have fruited by pruning them into shorter sections with loppers, then extracting them carefully to prevent their thorns snagging on new canes. Then untie the twine around the new canes and train them along the wires.
Blackberries can tolerate light shade, but they will be more productive in a sunny, sheltered site. They prefer moisture-retentive, but free-draining soil. If you have chalky, sandy, or heavy clay soil, improve with plenty of bulky organic matter (two bucketfuls per sq m) before planting.
They are usually bought as container-grown plants. A single plant can be incredibly productive, but if you plant more make sure they have plenty of room. Spacing depends on the vigour of the cultivar, ranging from 2.5m (8ft) to 4.5m (13ft) apart. When planting, cover the rootball with about 8cm (3in) of soil.
Vigorous cultivars need a sturdy support system. Use a wall or fence, 1.5-2m high, with horizontal wires spaced 45cm (18in) apart, with the lowest wire 23cm (9in) from the ground. Alternatively, run the wires between two strong vertical posts.
After planting cut down all canes to a healthy bud. This may seem drastic, but it will ensure plants throw up lots of vigorous, healthy shoots in spring.
Birds: Fruit such as berries are a magnet to many birds, who will strip the fruit from plants or peck holes in them.
Remedy: Either grow plants under a fruit cage, or wait until flowers have been pollinated then cover the plants with special, fine gauge bird netting.
Leafhoppers: The jumping, light green insects, roughly 3mm (1⁄8in) long, may occur on plants in sheltered sites, causing white flecking on the leaves.
Remedy: Control measures are not necessary.
Blackberry cane spot: This can cause grey spotting on affected canes, which sometimes spreads to foliage. As spots enlarge, canes may split and eventually die.
Remedy: Keep a close eye on plants and prune infected shoots out to ground level.
The fruit starts to ripen from mid-summer onwards. They are best picked as soon as they are ripe, and then either eaten fresh, frozen, or used in jams, jellies, and other cooking.
Mary Berry suggests this light fruit pear and blackberry dessert after a heavy main course.
‘Oregon Thornless': Dissected leaves that turn an attractive colour in autumn
‘Silvan’ AGM: Prolific crops of large fruit that ripen from mid- to late summer. Plants are vigorous and thorny, so need sturdy supports.
‘Loch Ness’ AGM: One of the most widely grown cultivars. The thornless canes bear masses of large, glossy, well-flavoured berries. These ripen from late summer until the first frosts.