During recent years, raspberries have been attacked by various types of virus. Many erstwhile good varieties have completely disappeared because of serious infection.
The East Mailing Research Station is doing a great deal to solve the problem using modern heat therapy as well as breeding new varieties of the Newburgh strain, which is disliked by aphids. Since it is the aphids that carry viruses from cane to cane, such plant selection should eventually eliminate the trouble.
SOIL AND PREPARATION
Raspberries prefer heavy soils to light sands, but also need good drainage. They react well to straw mulching systems on almost all soils because the surface roots are fibrous and do not penetrate more than 6 in. deep.
Dig the soil early in the autumn, putting plenty of cow manure or rotted compost at the bottom of the trench.
TYPE AND AGE OF CANES
Buy one-year-old canes. It is important that they should be virus free, and a Ministry of Agriculture inspection certificate number should be obtainable from the nurseryman.
Plant the canes in late autumn or early winter. Planting can be done as late as February, but can lead to difficulties if followed by a dry spring or early summer. Raspberries should be planted only on ground that is free from perennial weeds, for once the canes are in position, it is almost impossible to control such weeds as couch grass and creeping buttercup.
Plant the canes 1 ft. apart in rows 6 ft. apart. Remove the soil at the base of each cane carefully, and bury the roots so that the old planting mark is level with the soil surface.
Do not cut the canes down at planting time. Wait until February and then cut them back to a bud 1 ft. above soil level.
Apply straw all over the ground to a depth of 1 ft. in the middle of the month after planting. Because worms will pull loose straw into the ground, it will probably be necessary to add more straw each year, say a 3-in. layer, in mid-September to maintain the depth of the mulch. Each year, in early February, apply bone meal or a fish manure all over the straw at 4oz. per sq.yd.
Alternatively, apply well-rotted farmyard manure, compost or sedge peat along the rows in May, to a depth of 1 or 2 in. in the summer, lawn mowings may be applied along the rows also, but these should not be any deeper than 1 in. since they generate heat and may damage the base of the canes.
Every year, immediately after fruiting, cut down canes that have borne fruit to soil level to enable the young canes to grow properly.
In some gardens and with good varieties, canes may grow as tall as 8 ft. Cut these back in late February by about 1 ft. to make picking easier and to encourage the production of fruiting spurs lower down the canes.
There are, of course, autumn-fruiting raspberries. These must be pruned quite differently. Cut the canes down to within 5 in. of soil level in mid-February each year; the young canes that grow up will carry the crop in the autumn.
Provide posts with wires stretched between them to which the canes can be tied. Use 7-ft. Posts and treat the bottom 2 ft. with Cuprinol. Drive these posts into the ground about 15 ft. apart and stretch wires tightly between them, the bottom one at 3 ft. above soil level, the next 1 ft. higher up and a third l ft. higher still.
A less bothersome method is to provide parallel wires between which the canes can grow. Drive in a post at each end of the row and nail a piece of wood to each one to form a T. Stretch the wires tightly along the rows, attaching them to the ends of the T-pieces. Attach strong S-shaped wires at intervals along the wires to keep them together. This system is not suitable for very vigorous canes or in gardens subject to winds.
A third method is the roping system and is an extension of the first system. The tops of the canes are entwined round the top wire to form a kind of twisted rope. The effect is to make picking easier, and heavier crops may result.
Raspberries do not keep well, so always pick them on the day they are to be eaten. They should be ripe but still firm for dessert, but if they are to be used for making jam they must be fully ripe.
Lloyd George (New Zealand Strain). A summer and autumn-fruiting raspberry. Fruit rather hidden. Excellent for jam and quick freezing.
Mailing Enterprise, late. Dark coloured, large and good flavour. Excellent for freezing. This is apt to make too few-canes.
Mailing Exploit, early. Bright red. Fruit partly hidden by leaves. Excellent in south-west.
Mailing Jewel, early to mid-season. Delicious, firm and easy to pick. Excellent for jam or freezing.
Mailing Landmark, late. Soft, bright coloured. Thorny canes. Outstanding cropper. Useless for bottling.
Mailing Notable, early to mid-season. Large, sweet, red. Easy to pick. Specially good in north.
Mailing Promise, early. Large, good flavour. Produces plenty of cane. Heavy cropper. Not much good for bottling or freezing.
Norfolk Giant, very late. Dark red, delicious. Resistant to frost. Excellent for jam. Not a very heavy cropper, but useful because late.