Blackberries are a type of bramble fruit. These perennial plants fruit on biennial canes, which means the roots continuously send up canes. But flowers and fruit form only on 2-year-old canes. Blackberries come in thornless and regular (brambles have thorns) varieties. Both varieties are cultivated in the same way. Blackberries are further classified by how their canes grow: erect, semi-erect (sometimes called semi-trailing) and trailing. Trailing and semi-erect varieties should be trellised. To further confuse gardeners wanting to grow blackberries, marionberries, dewberries and boysenberries are all types of blackberries. There are hundreds of named blackberry cultivars available. Whatever cultivar you decide to plant, be sure to buy certified, disease-free brambles.
Plant blackberry brambles in early to midspring.
Choose a sunny spot that is at least 300 feet away from other bramble fruit and roses. Additionally, no members of the Solanaceae family (tobacco or nightshade family like tomatoes, eggplants, potatoes and peppers) should have grown in the soil for the previous three years to avoid spreading the verticillium wilt virus.
Test the pH of the soil where you will be planting the blackberries. The ideal pH for blackberries is 6.0, but they will tolerate a pH range of 5.5 to 7.0. Adjust the pH if necessary by adding limestone (if too acidic) or sulfur (if too alkaline).
Prepare the soil by digging 3 to 4 inches of compost into the top 5 to 6 inches of soil where you will be planting blackberries. Remove rocks and break up dirt clods. When you are finished, the soil should be fluffy and easy to work with.
Prune off all but three to five of the sturdiest canes. Shorten the remaining canes by half.
Dig a hole just deep enough for the roots. Blackberry plants need to be planted at the same level they were growing at in the nursery. Space trailing blackberries 5 to 6 feet apart, semi-erect blackberries 4 feet apart and erect blackberries 3 feet apart. If you are planting blackberries in rows, space the rows for all three varieties 10 to 12 feet apart.
Erect the trellis system for semi-trailing and trailing blackberries now. You can trellis blackberries against a fence, use individual trellises for each plant, trellis them against the side of a building or place two posts at either end of the row, string wire at 3 1/2 feet and 5 feet above the ground and attach the blackberry brambles to the wires using plant ties.
Fertilize blackberry brambles in early spring before buds begin to break with 2 to 3 inches of compost or a commercial 10-10-10 fertilizer. Follow package directions for rate of application.
Give your blackberry brambles 1 to 2 inches of water during the growing season, late March through September. Remember to include rainfall in the amount of water your plants receive.
Apply 3 to 4 inches of an organic mulch around and between plants. Mulch keeps weeds in check and keeps soil evenly moist, reducing stress on brambles.
Weed your blackberry patch regularly. Mulch will reduce the amount of weeding you need to do, but shallow-rooted blackberries cannot compete with aggressive weeds for nutrients and water.
Check your blackberry brambles for disease weekly. Signs of disease include yellow leaves, wilting canes, purple spots on leaves and gray streaking on canes, bright orange spots on leaves, a white or gray powdery substance on leaves and canes, curled leaves and brown spots on canes. Remove infected growth immediately, pruning 1 to 2 inches into healthy growth. Burn or bag infected plant material.
Pruning and overwintering blackberries
Prune lateral branches to 12 to 18 inches long in early spring and cut any winter-killed brambles off at the ground. Time this pruning with the application of fertilizer.
Prune canes that have borne fruit to the ground. Space first-year canes (canes that have not borne fruit) 6 inches apart by pruning weaker canes to the ground. The remaining sturdier first-year canes should be pruned back to 36 inches. Ideally you should leave three to five canes per plant.
Wait until your blackberry plant has dropped it's leaves to winterize. Pick up dead leaves before preparing your plant for winter.
Lay semi-trailing and trailing blackberry brambles on the ground and cover with 5 to 6 inches of shredded bark or straw. Remove the mulch in early spring before buds begin to swell and reattach canes to their support system.
Pile mulch or straw around the base and half-way up the canes of erect varieties. Remove when you see buds begin to form in early spring.