Blackberries (Rubus species) are a popular addition to many gardens, but their long-term growth habit often raises questions. Blackberries are definitively perennials, meaning the plant’s root system survives and regrows for multiple years. However, the above-ground stems, or canes, that produce the fruit operate on a two-year, or biennial, life cycle. This unique combination of perennial roots and biennial stems defines the blackberry’s growth and dictates how it must be managed for successful harvests.
Defining Perennials and Biennials
The distinction between plant life cycles is based on how long a plant survives. A perennial plant lives for more than two years, with its underground structure (root system or crown) persisting through dormant seasons to regrow new shoots annually. Many common garden shrubs and trees fall into this category, reliably returning year after year.
A biennial plant, in contrast, completes its entire life cycle over two growing seasons. The first year is dedicated to vegetative growth, establishing roots, stems, and leaves. During the second year, the plant flowers, produces seed, and then dies.
The Blackberry Paradox: Perennial Roots, Biennial Canes
The core of the blackberry’s biology is that its crown and root system are perennial, often living for ten to fifteen years or more. This persistent base allows the plant to return each spring. However, the individual stems, called canes, that emerge from this crown have a strictly two-year lifespan.
These canes are categorized into two types based on their age. First-year shoots are known as primocanes, which emerge from the ground and focus solely on vegetative growth. On most traditional blackberry varieties, primocanes do not produce fruit during their first season.
After surviving the winter, these first-year primocanes transform into floricanes in their second year. Floricanes develop lateral branches, flower, and ultimately bear the summer fruit crop. Once the floricane has finished fruiting, it dies back. Established blackberry plants always contain a mix of both new primocanes and fruiting floricanes simultaneously.
Managing Growth Based on the Life Cycle
The biennial nature of blackberry canes makes pruning techniques necessary for maximizing fruit yield and maintaining plant health. Since floricanes die after they produce fruit, they must be removed to make space for the next generation of canes. This removal is typically performed immediately after harvest or during the dormant winter season.
Removing the dead floricanes, which are often woody and brown, prevents disease and encourages the perennial crown to send up new primocanes. Gardeners also manage the first-year primocanes by tip-pruning them in the spring or early summer. Cutting back the tips encourages them to branch out, creating more surfaces for flower and fruit development the following season. This cycle of removing old wood and training new growth ensures a continuous supply of fruit year after year.