Raspberry

From flowering to the last picking, 1 to 1.5 inches of water a week

Once the flowers open, keep the planting at 1 to 1.5 inches of water per week until harvest ends, counting rainfall with a rain gauge. Water regularly rather than in occasional heavy soakings. Raspberry roots live in the top two feet of soil, so the plant has no deep reserve to coast on through a dry spell, and this is precisely the window when the berry is sizing. That shallow root system is why regular watering beats an occasional deep soaking.

Feed established rows in early spring, before growth starts

Before new growth begins, broadcast 4 to 5 pounds of 10-10-10 per 100 feet of row in a 2-foot band down the row, or use 50 to 100 pounds of barnyard manure per 100 feet instead. Go to the heavier end of the range if the row is mulched with sawdust, wood chips, or corn cobs, since the mulch ties up nitrogen as it breaks down. Raspberries carry a heavy crop on a shallow root system and are hungry feeders. Nitrogen delivered at the front of the season goes into building the primocanes that either fruit this fall or overwinter to fruit next summer.

⚠ Do not fertilize in late spring or summer. Late-season nitrogen pushes succulent growth that never hardens off, and it is that soft growth winter kills.

Cut out the spent floricanes as soon as they finish fruiting

On summer-bearing raspberries, cut every cane that just carried fruit right down to ground level and haul it out of the row. Tell them apart by the dried old fruit clusters at the top and on the laterals; leave the green first-year primocanes standing, because those are next year's crop. A raspberry cane dies after it fruits, and that dead wood is exactly where anthracnose, spur blight and cane blight overwinter and sporulate onto the new primocanes standing beside it. Extension is blunt about this: always remove floricanes after they have produced a crop.

Dormant pruning: thin summer-bearing canes to one every 6 inches

While the canes are dormant, take out any old floricanes you missed after harvest, then thin the remaining primocanes to the stoutest ones, leaving about one fruiting cane every 6 inches along the row. Cut winter-killed tips back to live wood. Crowded rows hold rain and dew for hours, and that leaf wetness is what the cane-disease fungi and gray mold need to infect. Thinning trades a few canes for airflow, light, and bigger berries on the canes that remain.

Fall-bearing rows: mow every cane to the ground while dormant

If you grow a primocane-fruiting variety and want one clean fall crop, cut all the canes to the ground once they are dormant, with a mower, sharp loppers, or a hedge trimmer. Pull out low trellis wire, twine, drip line, and soil sensors first. Skip this only if you deliberately want the smaller early-summer floricane crop as well. Fall raspberries fruit on the tips of first-year canes, so nothing standing is worth keeping; starting from bare ground gives one big concentrated crop and takes the overwintering cane fungi out of the patch along with the canes.

Black & purple raspberries: pinch the new canes when they reach knee-to-shoulder height

This is only for BLACK and PURPLE raspberries, not reds. When a first-year primocane reaches about 24-36 inches, snip an inch off its growing tip. Do it through the summer as canes reach that height, cane by cane. Leave red raspberries alone in summer — just water and weed them. Pinching the tip forces the cane to throw side branches, and those laterals carry next year's fruit, so a summer tip means far more berries per cane. Reds do not branch this way and need no summer pruning.

Raspberry cane borer: cut out wilting tips the week you see them

Walk the row through the summer watching for primocane tips that suddenly wilt for no reason. Look about 6 inches down from the tip for two rows of punctures girdling the cane roughly half an inch apart, then cut the cane about an inch below the lower ring. Burn the prunings or bag them and get them away from the patch. The female beetle girdles the tip with those two rings and lays her egg in the pith between them. The larva hatches and tunnels downward toward the crown, and a cane left alone can be killed outright. Cutting below the lower ring takes the egg out before it ever hatches.

⚠ No insecticide is needed for this pest - extension is explicit that chemicals are not necessary to control it. Cutting and destroying the girdled tip is the control.

Spotted wing drosophila: spray as the fruit colours, and mind the wait

Once the first berries start colouring, spinosad (Captain Jack's, Ferti-lome) is the home-garden material. Rotate to another chemical class after two consecutive sprays. SWD saws into sound ripening fruit and lays eggs under the skin, so maggots develop inside berries that look perfect. Treatment must begin when fruit first colours and continue through harvest.

⚠ BEES: raspberry flowers and fruits at the same time, so this spray can land on open blossom - spray at dusk when bees are not flying, and net rather than spray where you can. WAIT 3 DAYS after a home-garden spinosad spray before picking. Commercial Entrust is labelled 1 day on brambles, but the hardware-store bottle is 3 - follow the label in your hand, not the shorter number. Pyrethrins are 1 day but only rated fair against SWD. Do not make more than two consecutive spinosyn sprays.

Cane diseases: liquid lime sulfur as the buds break

Where anthracnose, spur blight, or cane blight showed up last year, spray liquid lime sulfur over the canes as the buds start into growth, while the emerging shoots are still short. These fungi overwinter in lesions on last season's canes and fire spores onto the tender new primocanes during the first wet spells of spring. Lime sulfur burns that overwintering inoculum off the bark before the new growth is exposed to it, which is why the spray only pays if it lands before growth gets away.

⚠ Lime sulfur must be applied before the emerging buds are 1/2 inch long, or plant damage will result. It is caustic, so wear goggles and gloves and keep it off your skin.

Gray mold: the spray that matters goes on at bloom, not at picking

Start when 5 to 10 percent of the flower buds are open, using captan. Spray again about 10 days later with a fungicide from a different FRAC group, and again at full bloom. After that, repeat only if the weather turns wet or the planting has a history of gray mold - do not spray on a fixed calendar through harvest. Botrytis infects through the open flower, not the ripe berry. It colonizes the healthy or senescing flower parts and sits latent inside the young receptacle until the berry sweetens, then erupts as gray mold, so a spray aimed at fruit you can already see is far too late.

⚠ These are fungicides, not insecticides - never put an insecticide on raspberries in bloom, because the open flowers are full of foraging bees; the New England guide's bramble table is blunt about this: DO NOT APPLY INSECTICIDES DURING BLOOM. Rotate FRAC groups between sprays; Botrytis builds resistance quickly. Mind the pre-harvest interval on the product in your hand: captan on brambles is 3 days to harvest, and Rovral (iprodione) is 0 days on caneberries. Read the label - it is the legal document.