Blackberry plants are available in erect, semi-erect, and trailing cultivars, or types. Additionally, you may choose from thorny and thornless varieties in all cultivars. The biggest difference between erect cultivars and semi-erect/trailing cultivars is that erect ones support themselves. Semi-erect/trailing cultivars require you to provide some means of support, such as using a trellis.
No matter what cultivar of blackberry you grow, blackberry roots are perennials, meaning they live on from year to year. Blackberry canes, on the other hand, are biennial. This means that their life spans the course of two years. The first year, canes are called primocanes. Traditional cultivars feature primocanes that do not bear fruit. However, the University of Arkansas has developed two cultivars that do bear fruit on primocanes, called Prime Jim and Prime Jane. Check with your local cooperative extension office to see whether these or any other cultivars are known to grow well in your area before considering them.
Most blackberry cultivars, barring Prime Jim and Prime Jane, only produce fruit during their second year of growth. Canes that were primocanes the year before are known as floricanes during this year. They produce flowers, which are then pollinated and bear the blackberries for which most people grow blackberry plants. Separate primocanes will grow at the same time, and will become the following year’s floricanes. Prime Jim and Prime Jane cultivars also bear fruit on floricanes, in addition to bearing fruit on their primocanes.
Once floricanes have borne fruit, you must prune the spent floricanes back to ensure the health and vigor of your blackberry plants. This process is known as topping, because you cut away the growth at the top of each plant. Only use sharp pruning shears when topping, so that cuts are clean and you run less risk of leaving your blackberry plants open to disease and insect infestation. Remember that pruning plants or trees effectively gives them open wounds; like wqith humans, you want those wounds to heal as cleanly as possible.
Over the winter, all blackberry plants go into a dormant period, where they concentrate their energy in their root systems and do not actively grow. Mulch the roots to a depth of at least 3 inches if you live in an area with harsh winters. Mulch helps protect soil and delicate roots from the effects of constant temperature changes that occur during very cold winters. Constant cycles of freezing and thawing can create a condition known as frost heave, where roots are forced aboveground by the earth’s constant temperature-related contractions. Think of mulch as a blanket, to help your blackberry plants get through the winter unscathed.