How to Grow Blackberry Plants
Blackberry jams, blackberry pies and berries eaten fresh and luscious right off the bush evoke the summer. Blackberries (Rubus fruticosus, U.S. Department of Agriculture plant hardiness zones 5 through 10) are relatively easy to grow in the home garden and can yield enough fruit for fresh eating as well as preserving.
Types of Blackberries
There are three different types of blackberries.
- Trailing: These cultivars produce long, drooping canes and some of the best fruit, with a robust flavor and small seeds. They're especially sensitive to cold and will sustain damage if winter temperatures drop below 13 degrees Fahrenheit or if spring temperatures dip into the 20s. Each plant will produce 10 to 13 pounds of fruit each year.
- Erect: Erect cultivars produce stiff, upright canes and can tolerate colder temperatures. The fruit is milder in flavor with larger seeds. Erect blackberry plants must be pruned and, as the least productive type, produce 4 to 6 pounds of fruit per plant, per year.
- Semi-Erect: Semi-erect blackberries grow on arching canes without thorns, and produce an abundance of mild fruit with large seeds -- as much as 25 to 55 pounds of fruit per plant, per year.
Choosing and Preparing the Planting Site
Blackberries are a perennial plant that can continue to produce for up to 20 years, so select a planting site carefully. Blackberries thrive best in a full-sun location, although they can tolerate partial shade. They can grow in a variety of soil conditions as long as the soil is well-drained.
Blackberries also benefit from a soil rich in organic matter, which improves water retention and drainage. The summer or fall before you plant, add about 2 cubic yards of organic material per 100 square feet, and work it into the soil.
Blackberries should be space according to the type of blackberry.
- Trailing cultivars should be spaced 4 to 6 feet apart.
- Erect cultivars should be spaced 2 to 3 feet apart.
- Semi-erect cultivars should be spaced 5 to 6 feet apart.
All blackberries benefit from growing on a trellis.
Blackberries are sold in two forms: bare root and tissue-cultured. Both types can be planted as soon as the soil thaws in the spring.
If you can't get your bare root plants into the ground right away, cover the roots with moist soil or sawdust to prevent them from drying out.
Dig a hole that will fit the roots without bending or breaking them.
Fill in the planting hole, pressing the soil with your hands until it's firm.
Water your blackberries immediately to help the soil to settle and to remove air pockets.
New blackberry plantings should be fertilized three times in the first year. Use 2 ounces of 16-16-16 fertilizer per plant for each application. Two weeks after planting, apply fertilizer to the surface of the soil around the plant. Reapply one and two months after the initial application.
New blackberry plantings should be watered weekly when they receive less than an inch of rainfall per week -- give new plantings an inch of water per week. Tissue-cultured plants need to be watered more frequently until they become established and should not be allowed to dry out. Mature plants continue to require 1 to 1 1/2 inches of water per week during the summer.
To prevent diseases caused by excess moisture on the leaves, water underneath the foliage, around the base of the plant, rather than watering overhead and wetting the foliage.
After the first year, blackberries should be fertilized three times early in the season to encourage new growth. Use 2 to 3 ounces of 16-16-16 fertilizer per application, per plant. Apply fertilizer to the soil's surface when you observe the growth of new canes in the spring, at the end of May and at the end of June.
It is important to control weeds in the soil around your blackberry plantings. Mulch can minimize weed growth. Weeds should be removed, but do not dig more than 2 inches below the soil or you risk damaging the roots of the blackberries.
Do not use landscape cloth or weed mats for erect types, as it can inhibit the growth of new canes.