Blackberries are a perennial plant, meaning they return year after year. There are many varieties, some with thorns, some without, some specially developed to produce sweet, large berries and others that grow wild with tart, tiny berries. Some grow to only 4 or 5 feet and resemble bushes while others grow long canes that can reach 8 or 9 feet in length. Whichever kind of blackberry you are interested in, they all share similar growth patterns.
Starting with Seeds
Blackberries produce their seeds inside the fruit which are called drupes. Drupes are fleshy fruits which encase their stony seed. In the case of blackberries, the drupes grow in a cluster, creating what we call a berry. Whether the berries fall to the ground, are picked by humans or eaten by animals, the seeds are easily transported and deposited where they quickly germinate and take root the following spring.
First Year Growth
Once planted, the blackberry seed must go through stratification, the process of enduring a winter with freezing temperatures before it can germinate. The warm temperatures and heavy rains provide the seed with all it needs to begin growing. In mid-spring, the plant produces the first-year canes, called primocanes. The primocanes do not blossom or bear fruit.
Second Year Growth
During the second year, more primocanes will sprout and grow. As the primocanes emerge, the second year canes, called floricanes, begin to leaf out. In late May to early June, the floricanes begin to produce blossoms. Following pollination and petal fall, the blackberries will begin to form, first as small, white berries before advancing to green, then red followed by black. Berries are ready to harvest by mid to late July.
Blackberry Plant Spread
Except for trailing types of blackberry plants, most will continue to send up new shoots annually. Left untended, the growth can become a tangled, gnarled mass of thorns. With some training and pruning, the blackberry bush will develop into a hedgerow, allowing easier harvest of its fruits. With each berry containing many seeds and being a favorite of birds and animals, new plants will begin emerging rapidly.
Because the seeds are easily deposited by birds and animals, the occurrence of unwanted blackberry bushes in places outside the designated site is high. Removal of young plants as soon as they are discovered is recommended to prevent invasive takeover by the blackberry plants. Once the plants have taken root and become established, they are difficult to remove.