How to Grow Boysenberries in Australia

Boysenberry (Rubus ursinus x Rubus idaeus) is a trailing bramble in the rose family, Rosaceae. It is grown for its large, dark red to almost black berries with a dusty bloom. It is thought to descend from blackberry, dewberry, raspberry and loganberry parents, and its fruit is so soft that it is rarely sold in shops.

Three mistakes that matter

1. Pruning the wrong canes. Berries grow on canes that grew the season before, called floricanes. Cut out the young canes in winter and next summer's crop goes with them. Remove only canes that have fruited, straight after picking, as Pruning and Training explains.
2. Planting without a trellis. Trailing canes left on the ground tangle into a thicket, hide the fruit and root wherever their tips touch soil. Build the trellis before planting, so the young canes have wires to go onto from the start.
3. Soil that is soggy or dry. Waterlogged, heavy soil invites Phytophthora root rot (Phytophthora species), and plants short of water in summer give small, flavourless berries. Plant into free-draining soil, raised if needed, then keep it steadily moist through flowering and fruiting.

When to plant

Plant bare-root canes in winter, from June to August, while they are dormant, and plant them as soon as they arrive. Boysenberry needs a cool winter to flower and fruit well, which rules out the tropics. The crown lives for years, so there is nothing to plant in succession.

If canes arrive before the bed is ready, heel them in: bury the roots in a shallow trench of moist soil until planting day. A dormant cane handles frost.

Site, soil and setup

Choose a permanent spot, because the plants stay for many years and dislike regular digging around their roots. Avoid ground where tomato, potato, eggplant, capsicum, strawberry or raspberry grew recently, since these crops can leave Verticillium wilt in the soil.

Planting Canes

Boysenberries start from a dormant bare-root cane planted beside a trellis that is already built. Raspberry, blackberry, loganberry, youngberry, tayberry, silvanberry and lawtonberry are separate plants, and each has its own guide.

Bare-root preparation

A bare-root cane arrives leafless and can look dead, but it is only dormant. Its roots dry out quickly in air, even while the plant rests, and dry roots can kill it. Unwrap the cane, shake off any packing material and trim off broken roots. Then stand the roots in a bucket of water with seaweed solution at 15 mL per 9 L while you dig the hole. Never put the packing material into the planting hole.

Building the trellis

Planting the cane

• Dig a hole as deep as the roots and twice as wide, beneath the trellis.
• Build a small mound in the bottom and spread the roots evenly over it.
• Backfill so the base of the stem sits level with the soil, no deeper than it grew before.
• Firm gently and water in with seaweed solution at 30 mL per 9 L.
• Cut the cane back to about 20 cm to balance the roots lost when it was dug.
• Mulch with straw, hay, lucerne or sugarcane, keeping it clear of the stem.

Due to quarantine restrictions and our shipping policy, we cannot send boysenberry canes to Western Australia or Tasmania.

Care by growth stage

Steady water, potash rather than nitrogen, and air moving through the canes decide the crop. The table follows one year of an established plant. A young plant follows it too, but usually gives its first real crop in its second summer.

Once berries start to colour, drape the trellis with white, wildlife-safe netting, stretched taut, with mesh too small to push a finger through. The trellis keeps the plants low enough to net easily. Check the net every day for trapped wildlife, and take it off promptly after the last picking.

Pruning and Training

Each cane lives two summers: it grows in the first, fruits in the second, then dies. Pruning removes the spent canes and trains the new ones, which carry next year's berries.

• After the last picking, cut every cane that fruited at ground level, then lift the new canes up to the top wire and retie them.
• If unsure, bend a cane: one that has fruited is brittle and snaps.
• Thin out weak, damaged or crowded new canes so air moves through the row.
• Bundle the strongest new canes and wind them along the lower wires, tying them loosely.
• In very fertile soil, tip-prune long new canes through summer to keep them manageable.
• Keep cane tips off the ground, and dig out suckers to replant or give away.

Companion planting

Boysenberries do best in a mulched strip of their own along the trellis, with low flowering plants at the edges.

Grows well with

• Alyssum, whose nectar-rich flowers draw pollinators and predatory insects to the row.
• Phacelia, which attracts hoverflies that eat aphids and feeds bees.

Keep apart

• Raspberry, which shares Phytophthora root rot and other cane diseases.
• Annual vegetables that need digging, which disturbs the spreading roots and crown.

Harvesting Fruit

Pick in early summer, when each berry has turned deep red-black, feels plump and slightly soft, and comes away with a gentle pull.

• Pick in the cool of the morning.
• Hold the berry lightly and pull, rather than squeezing it.
• Lay berries in a shallow container, since soft fruit bruises easily.
• Remove mouldy or damaged fruit as you go, and pick up fallen berries.
• Chill the harvest as soon as it comes inside.

Keep berries unwashed in the fridge, in a single layer between paper towels, and use them within 1 to 3 days. For longer keeping, freeze them spread on a lined tray, then bag them.

Eat them fresh, or turn them into jam, syrup, juice, pies and tarts.

Common problems

Plenty of leaves, few flowers. Mild winters give too little chill, a common result on the subtropical coast; see When to plant for the zones that suit it.

Small, dry, flavourless berries. Plants ran short of water while fruit swelled; see Three mistakes, and mulch thickly to hold moisture.

Sunburnt berries and leaves. Hot summer sun burns both, so drape shade cloth over the fruiting canes on hot days; see Site, soil and setup for a cooler position.

Fruit eaten before you pick it. Birds and possums take ripe berries; net the trellis as Care by growth stage describes. Read more

Brown spots on leaves. Leaf spot disease marks the foliage with brown spots; pick off affected leaves and thin the canes so air moves through the row.

Canes dying after harvest. This is normal for a cane that has fruited; see Pruning and Training.

Pests and diseases

Most boysenberry troubles start with wet leaves, wet soil or hot, dry spells, so the fixes are mostly about water and air.

Queensland fruit fly (Bactrocera tryoni). Boysenberry is a host in northern and eastern Australia, and Mediterranean fruit fly (Ceratitis capitata), widespread in south-west Western Australia, attacks it too. Females lay eggs in ripening fruit, and the larvae make the flesh decay. Pick promptly. Seal fallen or stung fruit in a plastic bag in the sun for at least 14 days, then bin it rather than composting it. In fruit fly districts, net with fine insect mesh, holes about 2 mm, since flies get through bird netting; close every gap. Read more

Two-spotted mite (Tetranychus urticae). These mites, about 0.6 mm long, feed under the leaves, leaving yellow-white speckling, bronzing and fine webbing. They build up in hot, dry summers, so keep plants watered and avoid sprays that kill predatory mites and lacewings. Read more

Grey mould (Botrytis cinerea). Flowers blight and ripening berries rot under furry grey mould after several cool, wet days. Remove infected fruit, open up crowded canes and go easy on nitrogen in spring.

Downy mildew (Peronospora species). Angular yellow blotches on the upper leaf turn red and purple, and infected green berries redden early, then shrivel and harden. It favours warm, humid, wet weather, so plant clean canes, keep the row open and bin old prunings.

Phytophthora root rot (Phytophthora species). New canes wilt and die back at the tips, leaves brown from the edges and the roots turn black to brown. It follows poor drainage, pooling water and heavy soil once the soil warms above 12°C. Drainage, not a spray, is the control in a home garden.

Prevention first

• Start with healthy, disease-free canes from a reliable nursery.
• Plant in free-draining soil and water the soil, not the plants.
• Thin and train canes early, and clear away old canes and prunings.
• Check leaf undersides and ripening fruit every week through spring and summer.

Tips

1. Tie a length of wool around each cane as it fruits, so the spent canes are easy to find at pruning time.
2. Short of space, run a two-wire trellis on outriggers fixed to a boundary fence.
3. To raise another plant, peg a cane tip into a pot of potting mix in autumn and cut it free once it has rooted. See layering.
4. One plant is enough for fruit, because boysenberry is self-pollinating.
5. Wear leather gloves and long sleeves to prune and pick, since boysenberry canes are especially thorny.