How to Grow Raspberries

How raspberries grow

Raspberry roots and crowns are perennial, but each cane lives only two years. In the first year it grows as a primocane. In the second it fruits as a floricane and then dies. Summer-bearing raspberries fruit only on those second-year canes. Everbearing types also fruit on the top of first-year canes from about August until frost. Red and yellow raspberries spread by root suckers and are grown as a narrow hedgerow. Black and purple raspberries send up canes from the crown, so each plant is kept as a separate clump.

Where raspberries do well, and where they struggle

Cool summers suit raspberries best. Red raspberries are the hardiest type: University of Tennessee Extension says properly acclimated plants survive about -20°F, while black raspberries are hardy only to about -5°F. Heat is the bigger limit for most gardeners. Tennessee calls raspberries a more challenging crop than blackberries and suggests elevations above about 2,000 feet in the Southeast. UF/IFAS does not generally recommend them for southeastern home gardens. In Arizona, University of Arizona Extension recommends fall-bearing types for the mid to high elevations of the north, and it warns against planting where walls reflect heat. In warmer parts of Maryland, raspberries benefit from light shade in late afternoon.

Choose a cultivar rated for your zone. Oregon State lists summer-bearing ‘Boyne’ (zones 3-7), ‘Prelude’ and ‘AC Eden’ (4-8), ‘Meeker’ and ‘Willamette’ (5-8), and ‘Cascade Delight’ (6-9). Its everbearing picks include ‘Heritage’, ‘Caroline’ and ‘Joan J’ (all 4-8) and ‘Polana’ (3-8), with black ‘Jewel’ (5-8) and purple ‘Royalty’ (4-8). For Tennessee, UT names ‘Dormanred’ as widely adapted across the Southeast and notes some heat resistance in ‘Nova’. Maryland lists its own release ‘Jaclyn’ for heat tolerance. Oregon State points out that an everbearing cultivar grown for the fall crop only can be grown in any of Oregon’s growing regions, including the cold ones, because no cane has to survive the winter.

Site and soil

Raspberry roots suffocate and rot in waterlogged soil, so drainage comes first. Oregon State wants the soil 2 to 3 feet above the water table and builds mounded beds at least 1 to 1.5 feet high on heavy ground. Aim for a pH of 5.6 to 6.5, and test the soil a year ahead so lime or sulfur has time to work.

Avoid ground that grew strawberries, potatoes, tomatoes, peppers or eggplant in the past several years. These crops host verticillium wilt, which hits black raspberries especially hard. Oregon State says five years and Arizona four. Plant away from blackberries, and at least 300 feet from wild brambles (Maryland). Buy certified virus-free plants rather than digging suckers from an old patch.

Planting

Plant bare-root canes as early in spring as the soil can be worked, usually several weeks before the last frost; see the dates for your zone above. Potted tissue-culture plants are often not hardened to cold and should wait until after the last frost. In California, UC IPM plants caneberries from mid-January to March.

1. Spread the roots in a shallow hole so the highest root is 1 to 2 inches below the surface.
2. Space red raspberries 2 to 2.5 feet apart and black or purple ones 3 to 4 feet apart, with 8 to 10 feet between rows (Oregon State).
3. Cut the canes back to about 6 inches and water often until new growth is well under way.

Trellis and pruning

Summer-bearing raspberries need a permanent trellis with wires near the top, about 5.5 to 6 feet high, and a lower set at about knee height. Everbearing and black raspberries do well on a simple T-trellis with a cross arm about 1.5 feet wide.

Summer-bearing reds: Keep the hedgerow 6 to 12 inches wide by hoeing out suckers that come up outside it. After harvest, cut the canes that fruited at ground level. In late winter, remove weak canes and tie the rest to the wires. Oregon State advises against tipping these canes in summer, because unbranched canes yield best the next year.

Everbearing reds: Keep the row 12 to 18 inches wide. For a single fall crop, cut all canes to the ground in late winter, which is the simplest option. For two crops, cut off only the dead upper part that fruited last fall, then remove the whole cane once it fruits again in early summer.

Black and purple: Pinch off the top 3 to 6 inches of new canes when they reach about 3 feet, going over the patch several times in early summer. Oregon State says this tipping raises yield four- to fivefold. In winter, shorten the side branches to 1.5 to 2.5 feet.

Water and feeding

Established plants need 1 to 1.5 inches of water a week, wetting the soil 6 to 12 inches deep. Drip line or a soaker hose keeps foliage and fruit dry. Mulch helps, but keep it off the crowns.

Nitrogen is the main need. Oregon State splits the year’s fertilizer into a dose when new canes start growing in spring and a second one 1½ to 2 months later. Everbearers can take a third, smaller feeding in midsummer to carry the fall crop. Canes taller than 10 feet with long gaps between leaves mean too much nitrogen.

Raspberries are very sensitive to glyphosate, so spray weeds near the patch with care, or pull them by hand.

Harvest

Ripe raspberries are fully colored and slip off easily, leaving the white core on the plant. Pick every three to four days, avoid picking wet fruit, and use shallow containers so the bottom layer is not crushed. Refrigerate right away and rinse just before eating. Chilled berries keep about a week. Oregon State expects 18 to 27 pounds per 10 feet of mature summer-bearing row, and somewhat less from everbearing and black types.

Common problems

• Phytophthora root rot: canes wilt and die in midsummer on wet, heavy soil. Raise the beds, and choose tolerant cultivars where root rot has been a problem.
• Raspberry bushy dwarf virus: crumbly fruit on otherwise normal plants. Replant certified stock in a new location.
• Spotted-wing drosophila: larvae in ripe berries, worst on late everbearing crops. Pick often, or use fine exclusion netting.
• White drupelets: sun and heat damage in hot, dry weather. Shade cloth helps.
• Frost: open flowers are injured at about 30°F, and fall frost ends the everbearing crop.