Top 10 Questions About Blackberries

By Amy Grant | December 16, 2018
Image by ruslan117
by Amy Grant
December 16, 2018

Here at Gardening Know How we get lots of questions, and our goal is to provide answers to those inquiries to the best of our knowledge. Some of the most common questions are about berries. While blackberries are generally fairly resilient, they do have their share of issues. Here are 10 most commonly asked questions about blackberry plants.


1. How do I prune blackberry canes?

Normally, tip pruning is done in the spring and forces the blackberry canes to branch out, thus creating more wood for fruit to grow on which equals more fruit in general. That said, pruning the blackberries to contain their growth will only promote lateral branch development, again increasing fruit production next year. Using sharp pruning shears cut the canes to about 24 inches (61 cm.) in length. Since blackberries only fruit on 2-year-old canes, also prune out the spent canes once the berries are done fruiting.

2. Green leaves and no berries. How to get blackberries on plants?

If the foliage is lush and healthy but lacking in berries, chances are good the plant is getting too much nitrogen. To tip the scales in favor of berries, amend the soil with phosphorus in the form of bone meal. Another reason for a lack of blackberries may be the youth of the plant. First year canes do not produce flowers or fruit, only second year canes. Lastly, if your plant has not produced berries, it may be a lack of pollination. Try adding some flowering native plants planted near the blackberries. Native plants will not only be most successful with the least amount of maintenance but will also attract local pollinators to the garden.

3. Can you grow blackberries in containers?

Absolutely, blackberries can be grown in pots. And, since blackberries can often get away from the gardener, container growing is a win/win, allowing for easy harvest and containment of the unbridled vines. Blackberry roots spread out rather than down, so select a wide rather than deep container. Provide a trellis to train the canes up. Remember that potted plants require more water and fertilizer than those in the ground. To further facilitate harvest, try one of the thornless varieties of blackberry. Prune container grown blackberries just as you would those in the garden.

4. How do you sweeten blackberries?

Some varieties of blackberry are sweeter than others. Also, when growing blackberries, they need sun and warm temperatures to really sweeten up. Provide the berry bed with a well-draining, organic rich soil as well. Provide the patch with an inch of water per week depending upon weather. Allow the berries to ripen until there’s barely a hint of rosiness and the color has dulled. If you pick the berries when they are still shiny, they will not be sweet. If you have already heeded all this advice, there’s one last resort”¦add some sugar to the berries.

5. How to winterize the blackberry vines?

If you take good care of your blackberries, you can plan on berries for 15-20 years. So, it is important to properly prune them and protect them from cold temperatures. The canes that have already fruited should be cut out. For caning varieties, cut trailing vines back to 12-18 inches (30-46 cm.) and with erect berries, remove the weaker canes leaving just 3-4 of the strongest. Depending upon your USDA zone, blackberries may need to be winter protected. Lay pruned canes on the ground and cover them with a thick layer of mulch.

6. White spots on blackberries, how to treat them?

Blackberries with white spots are probably the result of White Druplet Syndrome. Druplet refers to the individual ball on the fruit that surrounds the seed. There are a couple of reasons for this syndrome. First off, while blackberries love sun, it can be too much of a good thing. Berries exposed to hot afternoon sun and wind tend to be afflicted with white druplet more often than other exposures. In this case, the side of berry that is exposed to the sun will be white while the other side will be normal. Avoid planting in sunny areas exposed to hot summer winds and shade the plants after pollination has occurred. Pests can also cause white spots; the random patterning will be the tipoff that they are the result of pests.

7. Can you propagate blackberry?

Blackberries are very easy to propagate either via cuttings, suckers or tip layering. Propagating using leafy stem cuttings is the way to go if you want lots of plants. Just take 4-6 inches (10-15 cm.) of cane and place it in a moist peat/sand mix leaving 2-3 inches (5-8 cm.) out of the mix. Keep the medium moist. Root cuttings are the most common method of propagation. Take 3- to 6-inch long cuttings in the fall and cold store them for 3 weeks. After this period of cold storage, place the cuttings over a bed of moist peat/sand and lightly cover them. Cover the entirety with clear plastic and place in a shaded area until new shoots appear. Tip layering takes place outside. Just bend young shoots to the ground in the late summer/early fall and cover with soil. Sucker propagation is the easiest method. Simply remove the suckers from the parent plant and replant.

8. Why won’t my blackberries turn black or ripen?

Blackberries that won’t ripen are probably the result of redberry mite. Redberry mites spend the winter inside blackberry buds and scales. In the spring, the mites move on to new shoots and flowers and finally into the berries. The result – small, hard, inedible red or green berries. To treat the mites, prune out as many damaged berry clusters as possible. Then treat with horticultural oil or sulfur based insecticide. Timing is very important when treating redberry mites. The bush needs to be treated just after it breaks dormancy, as the buds begin to swell but prior to new leaves.

9. How and when do you transplant blackberry bushes?

Plan to transplant blackberries in the fall. Choose a full sun sight with rich, well-draining soil. Transplant in the evening to alleviate transplant shock. If you haven’t already done so, prune the plant, removing older canes that have already fruited and tipping new canes. Carefully dig up as many roots as possible. Dig a hole that is slightly deeper and wider than the root system of the plant. Place the plant in the hole and back fill, lightly tamping the soil to alleviate trapped air. In the spring, fertilize the plant as usual and begin giving the plant an inch of water per week depending upon the weather.

10. How to keep birds from eating the fruit?

Our feathered friends like berries as much or more than we do, and battling the birds can be an ongoing battle. You can hang many distracting or disturbing items near the berry patch such as old CD’s or predator decoys. Some people try to trap them, but you may inadvertently harm them. Draping the berry patch with netting is generally a successful ploy. There are also electronic repellents, noises that scare the birds away as well as chemical repellent options.

We all have questions now and then, whether long-time gardeners or those just starting out. So if you have a gardening question, get a gardening answer. We’re always here to help.

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