Blackberries Can Be Tough To Control

Blackberries are blooming now. While they do produce a tasty fruit, they are difficult to control in the home landscape and the thorns can be painful.

By Les Harrison
Wakulla County Extension Director

Spring 2017 has officially arrived in Wakulla County. The start began on March 20 at 6:29 A.M. eastern daylight time. .

With this seasonal milepost comes all the recurrent activities, many of which have a long tradition here in north Florida.  Dusting off the lawn and landscape maintenance equipment for the upcoming months of growing grass and shrubs is one of those practices.

Keeping a well-groomed yard and home landscape requires regular clipping of the foliage, some of which voluntarily appeared. Unfortunately, some of the “volunteer greenery” which is now emerging is quite difficult to control and nearly impossible to eradicate.

Compounding the problem, some species have thorns which usually discourage physical contact with the offending plant. One of the most common in Wakulla County is blackberries.

There are numerous members in the Rubus genus, which include blackberry, raspberries and dewberry species. Many of these are found in Florida and throughout the southeastern United States.

Blackberries are commonly found in or close to untended fence rows, ditch banks, and pastures, and can be overlooked for extended periods of time. The lack of management can give rise to thickets which are difficult to control and produce great volumes of seed which are easily disbursed to residential landscapes.

For the inexperienced it can be difficult to distinguish between dewberry and blackberry species found locally. However, the overall plant appearance and growth habits of these two distinct species are quite different.

Blackberries have a very upright growth pattern and commonly reach three to six feet in height. They also have hard, tough thorns without hairs.  Each plant is supported by a large lateral-growing root system which sprouts and produces additional plants in its root zone.

The rhizomatous root system is perennial, while the aboveground canes are biennial living for two years. The first year, the canes emerge and grow rapidly; the second year, the canes bud and produce flowers and fruit, and subsequently die after fruiting.

Dewberries have low, vine-like growth habits which rarely reach heights more than two feet.  Dewberry commonly has slender thorns with red hairs on the stem and seeds in their fruit are much larger and tougher than those in blackberry.

Herbicide application timing is important for effective blackberry control. This plant is most sensitive to herbicides when blooming in spring and in the fall prior to frost.

Applications made soon after emergence from winter dormancy or during fruiting are less effective. It is also important that the plants are not drought-stressed at the time of herbicide application.

Mowing is an effective practice if the goal is to restrain blackberry infestations to a manageable level until herbicide treatment timing is ideal. However, controlling blackberry by mowing alone is difficult and often ineffective because the large underground root structures are difficult to kill exclusively with mowing.

Blackberry propagates from both seed and rhizomes so mowing when blooming reduces seed production, but does little to stop the spread of blackberry rhizomes. Re-sprouting of the cut stems is common making additional mowing’s necessary.

The Rubus genus has existed a long time. Fossil records indicate there have been blackberries in central Europe since the Miocene Epoch or about 20 million years ago.

Given the nature of this plant, early residents were likely avoiding their thorns, even way back then.

To learn more about blackberries in Wakulla County, visit the UF/IFAS Wakulla County website at http://blogs.ifas.ufl.edu/wakullaco or call 850-926-3931.