Growing Red Raspberries: Rubus idaeus

Botanical Overview

A Rose family member, the Rubus genus has over 250 species. Rubus idaeus, Red Raspberry, occurs throughout the northern hemisphere. The modern commercial raspberry is a hybrid of several subspecies and varieties.

Description

Form: A bramble, composed of canes growing from root suckers.

Lifespan: Productive 4-20 years, depending on care.

Leaf retention: Deciduous.

Growth rate: Rapid.

Mature Size: Brambles are typically 3-5' (1-1.5m) high and as wide. The canes are often 9' (2.75m) long.

Flowers: White, five petals.

Bloom: Spring. Low chill plants often bloom early and their flowers can be damaged by late frosts, lowering fruit production.

Self-fruitful: Yes.

Years before fruiting: 0-1.

Fruit: The "berry" is an aggregate fruit, with many small round fruit clustered together, connected to a center part called the torus. When picked, the fruits release from the torus, and resemble bowls with a hollow centers. The berries do not ripen further if picked before they are ripe. Most cultivars have red fruit. Yellow fruited cultivar berries are sweeter, milder in flavor, and grow on everbearing canes.

Months for fruit to ripen: 1-1.5, depending on cultivar. They are ripe when they come off the vine with a very gentle pull, and must be checked daily. If too soft, they are over-ripe.

Storage after harvest: Eat immediately at room temperature or store in a refrigerator for up to 3 days. Freeze for longer storage. At room temperature, raspberries can start to get moldy in 2 hours.

Leaves: Dark green, fuzzy, wrinkled, toothed edges, 3-5 leaflets.

Stems: The canes are biennial, the rootstocks are perennial. The canes can be thorny or thornless, depending on the cultivar.
First year canes (primocanes) are green, second year canes (floricanes) are brown. Summer bearing canes produce leaves and stems the first year and bear flowers and fruit the second year, then die.
Everbearing canes produce vegetative growth the first year and bear flowers and fruit on the top one-third of the cane in the fall. The second year they bear flowers and fruit on the bottom two-thirds of the cane, then die.
Canes can take root where they touch the ground, often at the tips.

Roots: Shallow, spread by rhizomes, invasive in moist areas.

Cultivars of Note: for USDA zone 9 hot summers

'Anne' large sweet yellow fruit, bears summer into fall.

'Bababerry' / 'Baba Red' extra large red fruit, two crops.

Wildlife: The flowers attract bees, the fruit attracts birds and small mammals.

Toxic / Danger: Possible thorns.

Origin: Commercially grown raspberries originated in the non-desert regions of Asia, Europe, and North America.

Cultivation and Uses

USDA hardiness zones: From 4-8 to 4-11, depending on cultivar.

Chill hours: 250 to 1600 depending on cultivar. Plants needing 300 chill hours or less are more likely to bear fruit in USDA hardiness zones 9-11.

Heat tolerant: Usually not, but some cultivars show promise. Raspberries may fail when temperatures exceed 100°F (38°C) for hours.

Drought tolerant: No.

Sun: When temperatures are over 85°F (29.4°C), raspberries need 50% morning shade and 100% afternoon shade.

Planting: Locate raspberries on the east side of a west-facing wall in USDA zones 9 and 10. Protection with 50% shade cloth so that the plant never receives direct sun is recommended in temperatures over 85°F (29.4°C). Training to a fence or trellis is recommended. The support structure should be in place before planting. Planting in raised garden beds is best in regions with heavy rains. Raspberries can be grown in very large containers.

Soil: Well drained, at least 1' (0.3m) deep, 10-20% organic material, pH 6.0-6.5 (slightly acidic) is best.

Fertilize: Use an organic fertilizer, in early spring, spread in a two-foot circle around the plant, keeping 8" (21cm) away from the base.

Water after becoming established: Water at least weekly without berries, daily during flower and berry production. Do not allow the soil to dry out while flowering or fruiting. Water a circular area up to 3' (1m) from the base of the plant. Raspberry roots are shallow, not deep. One sign of insufficient water is berries that are small and crumbly.

Mulch: Spread organic mulch in a 3' (1m) radius, and 8" (21cm) away, from the base. This will reduce moisture loss and heat stress.

Prune: For summer bearing raspberries, cut the second year cane to the ground after its fruit have been harvested. For everbearing varieties, cut off the top one-third of the cane that has just borne fruit. In the summer, cut the remainder of that cane, having just borne fruit on its bottom two-thirds, to the ground.

Litter: Low to moderate.

Propagation: Red raspberry suckers (primocanes) may be cut away in the spring with a spade, taking a bit of the rhizome and roots with them. Plant in a location where they can be kept moist.

Pests: Raspberries are very susceptible to Verticillium wilt. Avoid planting in soils where previous plants had that disease. Nightshade family members and some rose family members are susceptible, so avoid soils where they have grown. Black raspberries are more susceptible to disease, so avoid planting red raspberries within 100' (30m) of them to reduce insect-spread diseases.

Uses: Edible fruit. The leaves are used for tea.

Comments

The black raspberry is a separate species: Rubus occidentalis. Purple raspberries are hybrids of red and black cultivars.

Raspberries often fail to flower or fruit in USDA zones 9 to 11 because of a lack of sufficient winter chill hours. Most gardeners living in these zones find blackberries to be a more reliable crop.

Do you have additional information or a different experience for these plants that you would like to share? Email info@GardenOracle.com. All contributions are welcome and appreciated.