How to grow raspberries

A raspberry crown is perennial and lives for years. Its canes are biennial: they grow one season and fruit the next, then die. What differs between the two types is *when* a cane fruits, and that single fact decides how you prune.

Summer-bearing raspberries fruit in early summer on canes grown the previous year — the old wood. You are always carrying two generations at once: this year's new canes, which will fruit next year, and last year's, which are fruiting now.

Autumn-bearing raspberries fruit in late summer and autumn on the tips of canes grown that same season. There is only ever one generation, which makes them dramatically simpler.

Now the trap. Autumn-bearers are pruned by cutting every cane to the ground in late winter — brutal, simple, and it produces a clean crop the same year. Do that to a summer-bearer and you have just removed every cane that was going to fruit, and you will get nothing at all. No wilting, no disease, no warning: just a healthy green row and no raspberries.

If you do not know which you have, wait and watch for one season. Fruit in June or early July on woody-looking canes means summer-bearing. Fruit from August onwards on soft green canes means autumn-bearing.

For summer-bearing, prune immediately after fruiting. The canes that just fruited are finished and will die anyway — cut them out at ground level. They are easy to identify: woodier, browner, and carrying the spent fruit stalks. Leave this year's new green canes, and thin them to the strongest six or eight per plant, tying them in as you go.

For autumn-bearing, prune in late winter before growth starts. Cut every cane to the ground. That is the entire operation, and it is why autumn raspberries are the right choice for anyone who does not want to think about it.

There is a trick worth knowing on autumn-bearers: instead of cutting all canes down, you can cut only half the row and leave the rest. The uncut half gives an early summer crop on old wood, the cut half gives the usual autumn crop — two harvests from one row, at the cost of slightly less fruit overall.

Whatever you grow, get the cut canes out of the bed rather than leaving them lying. Cane blight and spur blight overwinter on old wood.

Summer-bearing canes reach six feet or more and will arch over into the path under a load of fruit. They need support: two horizontal wires between posts, at about three feet and five feet, with canes tied in as they grow. Autumn-bearers are shorter and stiffer and often manage without, though a single wire keeps the row tidy.

The other thing to plan for is spread. A raspberry propagates by suckering — sending up new canes from the roots, sometimes several feet from the parent. Left alone a row becomes a thicket and then a nuisance, coming up in the lawn and the neighbouring bed.

Deal with it by walking the row once a month in the growing season and pulling — not cutting — any sucker outside the strip you have allotted. Pulling takes the bud with it; cutting leaves it to try again.

That suckering habit is also free plants. A sucker with roots, lifted in winter and moved, is a new raspberry, identical to the parent and completely free. It is how most raspberry rows in the world got planted.

Raspberries want cool summers, steady moisture and a real winter chill, and they resent heat and drought. That is an almost exact description of the maritime Northwest — which is why Oregon and Washington grow so much of the country's crop, and why a raspberry row in a Eugene garden asks for so little.

The one thing they will not tolerate is standing water. Cane fruit roots rot readily in ground that stays saturated through the winter, which in a wet-winter climate is the failure that actually happens. Plant on a slight ridge if your ground holds water, and improve drainage before planting rather than after.

They also want an acid to neutral soil and are unhappy above about pH 7 — chlorotic yellow leaves with green veins is the classic sign of lime-induced iron shortage.

Mulch generously. Raspberry roots run close to the surface, which is why they sucker so readily and why they dry out quickly. A thick annual mulch of compost keeps the roots cool, feeds the crown and suppresses the weeds you cannot hoe out without damaging roots.

Edward Payson Roe gives raspberries five chapters of Success with Small Fruits, which is on our shelf and free to read — more space than he gives anything except strawberries, and a sign of how seriously the crop was taken by a commercial grower on the Hudson.

One of his chapter titles is worth the price of admission on its own: The Raspberries of the Future. He was writing in 1881 about which species and hybrids would matter, and taking for granted that the answer was still being worked out.

The watercolour below is from the other end of that process. Marlboro was a leading commercial red raspberry of the late nineteenth century — the kind of variety Roe was arguing about — painted for the USDA in 1913 by Amanda Almira Newton, one of the artists the department employed to record fruit before colour photography existed.

It is worth knowing that these paintings were not decoration. They were the working record of what a named variety looked like, made because a written description could not settle a dispute about identity and a photograph could not yet show colour.