Thornless blackberries are an erect shrub with delicious berries from summer to early autumn. The fruit, which is produced in abundance on sturdy canes, strikes a perfect balance of sweet and tart. Wild blackberry is a pest in New Zealand, but the tamer, thornless hybrids are available to grow.
What you need to know about blackberries
Name: blackberry, bramble, Rubus fruticosus aggregate (various species and hybrids).
Height: thornless varieties generally 1.5-2m.
Spread: 1.5-2m
Plant type: upright, semi-deciduous or deciduous shrub.
Climate: cold, warm and cool temperate and arid.
Soil: moist, well-drained soil enriched with compost.
Position: full sun.
Foliage: each leaf is composed of three or five oval-shaped leaflets with serrated margins.
Flowering and fruiting: clusters of small white or pink flowers appear in late spring, followed by small green berries that change to red then black as they ripen.
Feeding: feed regularly throughout the growing season.
Watering: water regularly.
Appearance and characteristics of blackberries
Thornless blackberries are upright, semi-deciduous or deciduous shrubs that produce delicious edible berries from summer to early autumn. They are much tamer than wild blackberry, which is banned from sale and distribution in many regions of New Zealand. However, the varieties that are available to buy in nurseries are not considered a weed.
'Navaho’ and ‘Black Satin’ are popular thornless varieties. They are heavy croppers and need some support to keep them upright.
Uses for blackberries
The sweet-tart berries are delicious fresh off the cane and are also fantastic for baking in cakes or pies, or making into jam.
How to grow blackberries
Potted plants are available in stores year-round. Choose a spot in full sun with well-drained soil enriched with compost or aged manure. Blackberries prefer a slightly acidic soil with a pH between 5.5-6.5. Compost and manure will help increase the acidity of the soil, but powdered sulphur can be added if the pH is still too high. Plant blackberries where they will get support using either a trellis or two rows of taut wire along a fence or strung between sturdy posts. Tie canes to the trellis or wire as they grow.
Caring for blackberries
Fruit forms on two-year-old canes (floricanes). Once fruiting has finished, remove these canes, cutting them down to ground level. They will not fruit again.
Don’t remove the young canes that emerge during spring (primocanes) as these will fruit the following year.
How often should you water and feed blackberries?
Water regularly to keep the soil moist. Spread an organic mulch like pea straw or lucerne around the plants to help conserve soil moisture and keep the roots cool.
Apply fertiliser that’s specially formulated for fruiting plants every 8-12 weeks.
How and when to harvest blackberries
Expect fruit two years after planting. Pick berries when fully ripe – i.e. when the fruit is black and the juicy segments are plump and firm.
Diseases and pests that affect blackberries
Blackberries are generally trouble-free when it comes to pests and disease. In damp conditions, botrytis and rust may affect the foliage. If this happens, remove and discard any diseased leaves.
How to propagate blackberries
Blackberries are best propagated by tip layering.
To tip layer, dig a small hole near the blackberry plant, within reach of a flexible, current season cane (primocane) tip. Bend and bury the tip of the cane into the hole, firming down the soil. You may need to use a U-shaped peg or similar to help hold the tip in place. Water regularly to keep the soil moist. Roots should form within 8-12 weeks. Dig up and plant in a new location, if desired.
If you like this then try
Mulberry: a large deciduous tree with an abundance of sweet/tart red or dark purple berries from summer.
Kumquat: this small citrus tree is covered with sweet-tasting tangy fruit in the cooler months.
Pomegranate: a large bush or small ornamental tree with large round fruit packed with fleshy edible seeds.
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