Once established, a blackberry can fruit in cool gardens because the flowers appear late and therefore escape frost. They do not like being waterlogged in winter however, although they do like summer rainfall and sunshine, so don’t opt for a shady position.
When planting, try to add garden compost and keep your blackberry well watered in the first growing season and in subsequent dry summers. Mulch after spring rain in drier gardens, or if you have lighter soil. One bush should produce over 5kg (10lb).
Choose well, for blackberries vary greatly in habit and flavour. ‘Black Butte’ produce giant berries that are sweet enough to be eaten straight from the bush - although not in huge quantities. Others, like ‘Loch Ness’, bear a larger crop of good-sized fruit that’s sharper in flavour: these are better cooked or jammed. Generally the old fruiting wood is cut out after harvesting and this year’s canes are trained and tied in during autumn. However there is now a primocane blackberry called ‘Reuben’ which fruits on first year wood, producing gigantic, sweet berries. 'Reuben' needs to be cut back hard in autumn, rather like an autumn raspberry.
Try this recipe for blackberry and red wine jam
When to plant
Bare-root blackberries can be planted any time in the dormant season between November–March, or you can buy container-grown plants between spring and autumn and plant these. However containerised plants do need to be nurtured after planting.
How to plant
Dig in 5–8cm (2–3in) of well-rotted compost or manure thoroughly at the planting site. Space plants in rows 1.8m (6ft) apart if growing more than one, although one plant will often do in smaller gardens. Erect wire frames to support the branches and make picking easier. These should be in place prior to planting. Keep the area around blackberries well weeded.
How to train blackberries
The key to growing cultivated blackberries successfully lies in pruning and training. Most blackberries (except ‘Reuben’) fruit on last year’s canes from late summer onwards. Next year’s canes sprout from the rootstock from midsummer and their vigorous growth can get in the way of picking if the canes are blowing about.
One solution, perhaps the easiest if there’s room, is to train the new canes away from the old canes. The easiest system is to train all the new canes on one side of the supports, say the left, and have the old canes trained on the right side. If space is tighter, you can train the new canes vertically, in the middle of the old canes which are arranged like a fan on either side.
The new canes are gradually gathered together into a tight bundle which is fixed to the frame in the twelve o’clock position. The old canes are cut away after fruiting and the bundle of new canes is left in place over winter. In February the bundle of canes is undone and then spaced out on to a frame, often a wooden T, or fixed to wires with soft tie.
Try to train yours into positions where the branches pick up afternoon sunshine, even if the roots are in shade, and try to get the branches as horizontal as possible. The more level the cane, the more flower is produced because the sap flows more slowly.
Blackberries and wildlife
Blackberry flowers are extremely attractive to bees and butterflies – they do not need a partner close by to set fruit. However, fruit set is heavier if your blackberry is in a sheltered position. Our wild blackberries are a complex group of 350 micro-species and in some areas the bushes yield large fruit. In other places the berries are poor.
Wild blackberries propagate by tip-rooting so if you want a new blackberry, just bury the tip of one branch into the soil and it should root with alarming speed.
It’s a good idea to dig lightly under the canes in winter to uncover any pests lurking in the soil. With luck, the birds will eat any overwintering raspberry beetle larvae, because these also attack blackberries. Then top-dress the area with a general fertilizer like Vitax Q4 in spring.
Best varieties of blackberry plants to grow in the UK
An early-fruiting variety producing large clusters of flavourful, round berries from late July to August. A very vigorous variety – not suitable for a small garden.
This thornless blackberry produces very high yields of top-quality fruit. Berries are large, very firm and glossy black. The most successful commercial variety in Britain.
A new, very early variety from New Zealand. This ‘King’ blackberry produces elongated fruit by July and carries on for two months. The fruit is easy to pick. (from Blackmore Nurseries - www.blackmoor.co.uk).
A thornless blackberry with divided leaves that crops in late August or September. Can be safely planted against a wall or fence as it has smooth stems. A lighter cropper so not suitable if you want lots of fruit.
This new primocane blackberry is cut back every year. It produces large, sweet fruit but can be harder to establish than some.
The loganberry, a cross between a raspberry and a blackberry made by Judge Logan in California in the 1880s, needs at least 12 - 15ft (up to 5 m). It bears juicy fruity with a sharp flavour and it’s best to leave the fruit until it’s a dark-red before picking. Loganberries are usually used for jams and summer puddings, but really ripe fruit can also be eaten fresh. The fruit ripens over a long period, between August and September, and the yield is heavy so if you have room they are worthwhile. Most modern loganberries are thornless.
This American berry is widely grown in warmer states like California and you may succeed with it if you have a warm garden. The boysenberry is a cross between a European Raspberry, a Common Blackberry and a Loganberry originally developed by an Californian farmer called William Boysen in the 1920s. The large, shiny fruit is dark maroon but can be watery.
This relatively recent hybrid (between a red raspberry and a blackberry) was developed in Scotland in 1979 on the banks of the River Tay - hence the name. The fruit is large and very sweet. but it does not come cleanly away in the hand when you pick so it has never become a commercial success.
Did you know...?
In medieval England it was widely believed that the devil spat or urinated on all the fruit in the hedgerows on Michaelmas Day, September 29, so country-dwellers eschewed them after that date. Late fruit does tend to ferment, giving them a strange flavour.
Try this recipe for blackberry and apple upside down cake