Best Tips for Growing Blackberries
There are many gardeners who feel, with some justification, that a fine blackberry is the best-flavoured of any soft fruit; and I think I would probably agree. The biggest problem hitherto has been that the flavour of the garden varieties by and large fell short of that of the best wild blackberries. But simply planting a wild blackberry in your garden would soon result in an unmanageable tangle. Some of the newer cultivated varieties do approach the real wild blackberry in flavour, however, and although their flexible canes will always be a little more fiddly to train than the stiff ones of raspberries, the effort is well worthwhile.
HISTORY AND TYPES OF BLACKBERRY
The wild blackberry or bramble is a very variable group of plants, a complex of numerous related species that botanists conveniently classify together under the name Rubus fruticosus. The group includes the typical flexible-caned brambles that you will find in the hedgerows and anyone who has picked wild blackberries from them will know how much one plant differs from the next in the size and number of fruit, the shape of the leaves, the vigour and in many other ways. One fairly distinct type is the dewberry, Rubus caesius and in North America this name tends to be used to distinguish the trailing types from some more erect, stiffer-caned forms called erect blackberries. The various garden varieties have been bred or selected from different species within the overall blackberry group and among the more distinct types are the cut-leaved or parsley-leaved blackberries, derived from Rubus laciniatus, and a number of thornless types selected from Rubus rusticanus inermis. There are even types with very pale orange berries, called, would you believe, white blackberries. In recent years, some of the American upright-growing species have been used in European breeding programmes to develop new, more easily trained blackberry varieties such as ‘Loch Ness’.
In common with raspberries, blackberries were not planted in gardens until relatively recently because wild fruit was always available and because the plant can be such an untameable monster. It was probably not cultivated to any extent until the end of the eighteenth century but should certainly have a place in the modern fruit garden, provided care is taken in choosing an appropriately manageable variety. Most blackberries form theirand fruit on the previous season’s canes, much like summer-fruiting raspberries although there are exceptions and the very vigorous ‘Himalayan Giant’, derived from Rubus procerus will form fruit on older canes too.
Blackberries grow best in well drained, medium loam with a pH around 6.5 although they are moderately tolerant of slightly heavier soils. On very light and dry soils, they will be feeble and produce a small rather pathetic crop. Both heavy and light soils should be improved with organic matter before planting. However, it is scarcely worth persevering with blackberries on very thin chalky soils where the combination of water shortage and nutrient deficiency will always make a battle of their cultivation.
Blackberries are moderately shade-tolerant but will crop best and produce the sweetest fruits in full sun. They are particularly prone to damage from hard winter frosts and also from very cold winter winds and should therefore be given some shelter in cold or exposed areas. Planting them against a sunny, sheltered fence or wall is ideal, as only a few plants are likely to be needed and they are seldom required in such quantities as to necessitate planting long rows. New crops are always best planted away from that has previously been used for growing other blackberries or related plants such as raspberries. In most areas, blackberries will require decent protection from birds. Ideally this should be provided by planting them in a fruit cage, although when they are grown along a fence or wall, other less sophisticated methods of netting them may be used.
Winter, especially early winter, is the best time for planting blackberries although they will establish fairly well at other times of the year. As they tend to be sold bare-rooted rather than in containers, however, summer planting is rarely an option. The planting hole should be dug at least 45cm (18in) deep and of similar width with plenty of well rotted manure or compost and a handful of bone meal. Lightly trim the fibrous roots before planting, spread them evenly and plant with no more than 8cm (3in) of soil over them. If white shoot buds are present, these must be only just below the soil surface. Firm the soil carefully and slope it slightly away from the canes. Water well and top up with a mulch of manure or compost. Immediately after planting, cut back the canes to just above a bud about 25cm (10in) above soil level, if this hasn’t been done by the nursery.
In many gardens, a single plant will be sufficient to provide a modest crop but where several plants are grown, they should be widely spaced. The less vigorous varieties should be placed 2.5m (8ft) apart within the rows, with 2m (7ft) between rows. The more vigorous types should be placed 3.5-4.5m (12- 15ft) apart within the rows, with 2.5m (8ft) between rows. It is for this reason that I say many gardens will really accommodate only one plant. The major exception to this is the new, rather stiff-caned variety ‘Loch Ness’ which can be planted at a spacing of 1m (3ft) each way.
Otherwise, not only will their canes make a tangled mass of growth, from which it will be very difficult to pick the fruit, but they will also be impossible to prune and the yields will, in consequence, be poor. All conventional training methods are best done with the plants supported against horizontal plastic-coated straining wire of approximately 10 gauge. Four wires should be spaced 30cm (12in) apart, with the lowest 1m (3ft) above soil level. The wires may be attached either to stout vertical posts or to vine eyes screwed to a wall or fence.
Numerous methods have been devised to train the long flexible canes but some are very difficult to do satisfactorily and I shall confine myself to two: the fan which, although rather time consuming to tie-in, is fairly easy to create and gives the highest fruit yield; and the rope which is very simple and quick to do but gives a considerably smaller crop.
Both can be done on the single bay or alternate bay systems — two techniques designed to separate the new from the old canes. In the single bay method, the new canes that will bear next season’s fruit are tied up through the centre and then out along either side and over the top of the old canes that bear the current year’s crop. In the alternate bay method, the old and new canes are separated by training one batch to the left and the other to the right. If you use the single bay system, you should expect a slightly higher crop because the canes aren’t quite so close together.
You will sometimes see rather more ornamental training methods used — over archways, for example, and there is no reason why you shouldn’t experiment. But always bear in mind the need to keep fruiting and new canes apart. And of course, you will be unlikely with these decorative methods to obtain as big a yield or to keep birds at bay.
PRUNING AND CANE THINNING
Pruning comprises cutting off the old canes at soil level as soon as they have fruited in early autumn. By this time, they generally look pretty unsightly. If you are using the single bay system of training, the new canes must then be retied in their place. With the alternate bay method, this isn’t necessary. But with both systems, the young canes that emerge during the following spring will need to be tied, in turn, into their place. If the canes are much too long to fit into the horizontal space available, then cut off as much as is necessary from the tips.
On good soil, a very large crop of canes may be produced, especially from the more vigorous varieties but about 24 canes per plant is the maximum that should ever be retained. Any in excess of this should be cut out at soil level, selectively choosing, of course, the weaker ones for removal. Suckers that emerge at a distance from the plant should be pulled away if possible; if not, then severed with a spade.
FEEDING, WATERING AND WEEDING
The same procedures may be used as described for raspberries although, in my experience, blackberries are much less prone to suffer any damage from hoeing too close to the base of the plants. However, if at all possible, any wild brambles growing in the vicinity should be cleared away, as they could operate as a potential source of virus and other disease contamination for your plants.
YIELDS AND QUANTITIES OF PLANTS NEEDED
Yields vary greatly between varieties and also with the training method used. The best varieties, fan trained in good growing conditions may yield about 13-14kg (30lb) of fruit per plant, but in many gardens it will be much less than this. Yields will always be depressed by autumn frosts which bring fruit ripening to an end, so in areas where early frosts are to be expected, you should always concentrate on early-fruiting varieties.
HARVESTING AND STORING
Blackberries should be picked as soon as the fruit are truly dark. Several pickings will be needed over a period of a few weeks but it’s wise not to pick in wet weather when the fruit are easily squashed and prone to grey mould rot. Because the fruit do not part from the plug and require pulling rather firmly, it is best to try to pick them by holding the stalk rather than the fruit itself. Blackberries will remain fresh in a refrigerator for about a week and can also be made into jam or frozen. However, freezing is a fiddly business because the stalk stubs must be cut off and the fruit do not, in any event, retain their form particularly well.
Blackberries are relatively free from problems.
Bedford Giant, late July to August. Large, sweet and juicy. Strong grower.
Himalaya Giant, August to September. Large, dull. Plant 15 ft. apart.
Marion (a new American introduction), August. Bright black, superior flavour. Extremely heavy cropper.
Merton Early, August. Shiny, very delicious. Plant 6 ft. apart.
Merton Thornless, mid-August to end of September. Large fruit. No prickles on the canes.