Raspberry

Light and exposure

The raspberry accepts full sun as well as partial shade, and that flexibility is an asset because it can be tuned to the climate. In full sun, the fruit is sweeter and ripens earlier; at the edge of a wall or under a light tree, the soil stays cooler in summer, which the plant appreciates. The hotter and drier the summer, the more the afternoon shade helps; under a cool summer, aim for full sun instead.

Avoid the corners where the air stagnates and where moisture never dries, because that is where fruit diseases settle in. An airy spot, facing east or west, sunny a good part of the day, gives the best results.

Watering

The raspberry forms on soil that stays cool, that is the key to a fine harvest. In summer, especially from flowering to fruit ripeness, water as soon as the soil dries at the surface. A lack of water at that moment gives small, dry fruit.

Water at the base and in the morning, not on the foliage or the clusters. A mulch of compost, dried grass clippings or dead leaves keeps the moisture in the soil and limits watering. The rest of the year, under a damp temperate climate, the rain amply covers the needs; under a dry or windy climate, watering stays necessary from spring to autumn.

Soil and repotting

The raspberry wants a soil that is cool, rich in humus, light and rather acidic. It hates two things: lime, which turns its foliage yellow, and stagnant water, which rots its roots. If your soil is heavy or chalky, amend it with compost, leaf mould or ericaceous soil, and plant on a slight mound to drain.

Bare-root planting in autumn is ideal: the plants settle in over winter and start strongly in spring. Space the plants 40 to 50 cm apart along the row and set up wires stretched between two posts to train the canes, otherwise they collapse under the weight of the fruit.

Temperature and humidity

Cold is not the issue with the raspberry. Dormant canes take -25 °C without damage, and the hardiest cultivars go lower still under a blanket of snow: the plant is at home from USDA zone 3 to 8 and spends the winter outside without any protection. It even needs cold to break its dormancy, 800 to 1600 hours below 7 °C depending on the cultivar.

What it dreads is heat: growth is at its best between 22 and 25 °C, and beyond 32 °C the berries stay small, the yield drops and the quality suffers. A cool, humid summer and a mild but wet winter, and the raspberry needs nothing more. Under that regime, the point to watch is not frost but excess water in the soil during the cold season: a plant set in a waterlogged hollow can see its roots rot.

Pruning and upkeep

It all depends on the type. Non-everbearing raspberries give a single harvest in summer on the canes grown the previous year. After the harvest, cut those canes that have fruited right down, they will not fruit again, and keep the young green shoots of the year: these are the ones that will bear the fruit the following summer. Train them and thin them out to keep only the most vigorous.

Everbearing raspberries fruit in autumn on the canes of the year, then a small time the following summer on those same canes. The simplest method, and the one recommended for a home garden, is to cut everything right down at the end of winter: you give up the small summer harvest but you get a single large autumn harvest, without ever having to tell the old canes from the new.

Pests and diseases

Under a damp climate, watch the fruit first. Grey mould, botrytis, covers the raspberries with a grey felt in rainy weather, especially at the end of the harvest: remove the affected fruit and air the planting. Powdery mildew can whiten the foliage, and rust can mark it with orange pustules during very wet summers.

As for the pests, the number one enemy is the raspberry beetle, whose larva, the small white grub found in the fruit, spoils the harvests. Everbearing varieties cut right down partly escape this pest, because their late fruiting falls outside its peak. Also watch for aphids on the young shoots.

Propagation

The raspberry multiplies on its own, and even a little too much. It sends up suckers, those shoots that come out of the ground at a distance from the mother plant. You just have to dig up a well-rooted one in autumn or at the end of winter, with a portion of root, and replant it elsewhere: you have a new plant for free.

This is also how the plant becomes invasive. Taking the suckers therefore serves both to multiply and to contain the raspberry patch. Sowing exists but has no interest in the garden, because plants raised from seed do not resemble the original plant.

Month-by-month care calendar

Green Hub tips

• Take an everbearing raspberry and cut it right down at the end of winter, before growth restarts: a single pruning in the year and a large autumn harvest, it is the simplest choice.
• Never any lime or stagnant water. Amend with compost, plant on a slight mound if your soil is heavy and mulch to keep the soil cool.
• Contain the suckers as soon as they spill over the row, a spade cut in spring is enough, otherwise the raspberry invades the whole bed.
• A well-rooted sucker dug up in autumn replants elsewhere and gives a new plant for free: it is the simplest way to multiply.