How to Grow Blackberries in Australia

Thornless blackberry (Rubus hybrid) is a cane fruit in the rose family, Rosaceae, grown on a trellis for its sweet black berries in summer. Its smooth canes make training and picking far kinder than on a wild bramble, but wild blackberry is one of Australia's worst weeds. Each state sets its own rules on which cultivars may be sold, so the mistake that matters most happens before planting.

Three mistakes that matter

1. Planting without checking the law. Wild blackberry is a Weed of National Significance, and several states ban its sale except for named cultivars. Check the state table in Planting Canes before you buy.
2. Leaving fruited canes in place. A cane that has fruited will not fruit again, and left standing it crowds the plant, traps humid air and shelters disease. Cut it to the ground after harvest, as Pruning and Training explains.
3. Dry soil from flowering to harvest. Without steady moisture the berries stay small and lack flavour. Mulch the row, water deeply through spring and summer, and do not plant where water runs short from October.

When to plant

Plant bare-root canes in winter, from about June to August, while they are dormant and leafless. Plant them as soon as they arrive, on a day when the soil is neither frozen nor waterlogged. The crop depends on a cold winter: canes need winter chill to flower well, which is why the warm north misses out.

A cane planted in winter spends its first summer growing new canes, and those fruit the following summer. Expect a light pick at most in the first season.

Site, soil and setup

Do not plant where tomatoes, potatoes, eggplants or capsicums have grown in the last three years. Their soil can carry Verticillium wilt (Verticillium dahliae), a soil-borne fungus that sometimes infects blackberry.

Planting Canes

Blackberries start from a dormant bare-root cane, a single stem with its roots, planted straight into its place on the trellis. Due to quarantine restrictions and our shipping policy, we cannot send Blackberry Thornless canes to Western Australia or Tasmania.

Check your state's weed rules first

Exemptions go by cultivar name, so a cane sold only as a thornless hybrid, with no cultivar named, cannot be shown to be exempt. Ask the seller for the cultivar name before you buy. Declarations change, so confirm the current list with your state's biosecurity agency. Raspberry, boysenberry, loganberry, youngberry, tayberry, silvanberry and lawtonberry have their own guides.

Bare-root preparation

A dormant cane looks lifeless, but healthy stock has plenty of fine, fibrous roots, a strong stem and two or three green shoots or buds. Keep the roots moist from the moment the parcel opens, and never leave them lying in the sun. Cut off any damaged roots. Then stand the rest in a bucket of seaweed solution at half strength (15 mL per 9 L) while you dig the hole.

Planting on the trellis

• Dig a hole as deep as the roots and twice as wide, centred under the trellis wires.
• Fan the roots out and set the cane at the depth it grew before, or 3 to 5 cm deeper.
• Backfill with the improved soil, firm gently and water in with seaweed solution at 30 mL per 9 L.
• Cut the planted cane back to two buds; the new fruiting canes grow from the crown each spring.
• Mulch with straw, hay or sugarcane mulch, not woodchip.

Care by growth stage

Steady water, a light hand with nitrogen and potash from flowering decide the crop. Months follow the southern season and shift a few weeks earlier in warmer districts.

Net the trellis once the first berries colour, using white, wildlife-safe netting stretched taut. Choose mesh 5 mm or smaller at full stretch, which Victoria and the ACT require by law. The trellis keeps the plants low enough to cover. Too much nitrogen in spring gives soft, leafy growth that grey mould and aphids favour.

Pruning and Training

Each cane lives two summers. In its first it grows long and leafy (a primocane). In its second it sends out short side shoots that flower and fruit (a floricane), then dies. Pruning keeps the two apart on the trellis.

• Through spring and summer, tie new canes loosely in a bundle on the top wire, clear of the fruiting canes below.
• Pinch out the tips of new canes once they reach the top wire, which encourages branching.
• Keep cane tips off the ground: where a tip touches soil it roots and starts a new plant.
• After the last picking, cut every fruited cane to ground level.
• Untie the new canes, keep about six strong ones on a young plant, and fan or weave them along the lower wires.
• In winter, dig out any suckers that appear away from the row.

Bag and bin the prunings rather than composting them, since cane spot and downy mildew (Peronospora sparsa) survive on old canes and leaves.

Companion planting

A blackberry row is permanent, so keep companions low and to the edges where they will not shade the canes or compete for water.

Grows well with

• Alyssum, whose nectar-filled flowers draw pollinators and predatory insects to the row.
• Phacelia, which draws hoverflies whose larvae eat aphids.

Keep apart

• Roses, which host the same downy mildew.
• Wild blackberry, which hosts downy mildew and redberry mite (Acalitus essigi).

Harvesting Fruit

Pick berries when they have turned from shiny to dull black and begin to soften; unlike a raspberry, the core comes away inside the fruit.

• Check the canes every few days once fruit starts to colour.
• Pick in the cool of the morning.
• Lay the fruit in shallow containers so the bottom layer does not crush.
• Take off damaged or mouldy berries as you go, and bin them.

Store the berries unwashed and uncovered in a shallow container in the fridge for one to two days, and wash them just before eating.

Eat them fresh, or freeze them and cook them into jam, pies and sauces.

Common problems

Few flowers after a mild winter. Too little winter chill, as When to plant explains, often gives light crops on the coast and in warm districts.

White or tan drupelets (the juicy segments of the berry). A sudden rise in temperature with low humidity and wind lets ultraviolet light damage exposed berries; afternoon shade can reduce it.

Canes wilting and tips dying in warm, wet weather. Phytophthora root rot (Phytophthora species) attacks roots in poorly drained soil, turning them brown to black; raise the row and do not overwater. Read more

Purple spots with grey centres on young canes. Cane spot, a fungus spread by rain splash, weakens canes; start with clean stock, keep rows open and remove prunings.

New plants popping up along the row. Cane tips that touch the soil root and form new plants; see Pruning and Training. Read more

Berries eaten before you pick them. Blackbirds and other birds, and possums, take ripe fruit; net the trellis as Care by growth stage describes. Read more

Pests and diseases

Most blackberry troubles follow the weather: mites build up in hot, dry spells and fungal diseases in humid or wet ones.

Two-spotted mite (Tetranychus urticae). These mites, about 0.6 mm long, feed under the leaves and leave them speckled and bronzed, often with fine webbing. They thrive in hot, dry, dusty conditions, so keep the soil moist and avoid sprays that kill predatory mites. Read more

Redberry mite (Acalitus essigi). This tiny whitish mite shelters in buds and at the base of the fruit. It leaves some drupelets hard and red while the rest ripen black. Cut out fruited canes promptly, and control any wild blackberry within 100 m, which harbours it.

Queensland fruit fly (Bactrocera tryoni). Females lay eggs in ripening berries, and the maggots rot the fruit from inside. Where fruit fly is active, cover the row with fine insect mesh once fruit sets, sealed to the ground, with berries clear of it. Pick promptly. Kill the maggots in fallen or stung fruit before binning it. Freeze it, or seal it in a bag in the sun for at least 14 days. Read more

Grey mould (Botrytis cinerea). Flowers turn brown and grow grey fuzz after a few humid days, and the fungus spreads to the berries. Keep the canes thinned and tied so air moves, and pick off infected fruit.

Downy mildew (Peronospora sparsa). Angular yellow patches on the upper leaf turn red and purple, and infected green berries redden early, shrivel and harden. It favours warm, humid weather, so train canes openly and remove old prunings.

Blackberry leaf rust (Phragmidium violaceum). Released to control wild blackberry, this rust leaves purple-brown blotches on leaves, with yellow or black pustules beneath. Some thornless hybrids are susceptible, so in rust-prone districts ask your state agriculture department about resistant stock.

Prevention first

• Start with clean, healthy canes of a cultivar permitted in your state.
• Water the soil, not the canes, and keep the row open and well tied.
• Prune and bin as Pruning and Training describes.
• Spray aphids with pyrethrum only when numbers build up. It harms bees, so spray late in the day away from open flowers, following the label and its withholding period.

Tips

1. Keep the plant label or receipt showing the cultivar name, in case a weeds officer asks.
2. Mark each spring's new canes with a coloured tie, so there is no doubt which to cut after harvest.
3. Tie canes to the wires with soft, stretchy ties, which do not cut into the canes as they thicken.