Blackberries (Rubus spp.) make a fun addition to the home garden. Many families have a tradition of picking blackberries together for pies. Cobblers, fruit bars, jams and juices are other yummies that you can make with the kids' help. Blackberries are also good on cereal and fresh off the bush. Members of the rose family (Rosaceae ), blackberries prefer U.S. Department of Agriculture plant hardiness zones 6 through 8. On the downside, blackberry brambles bear wicked thorns that can make weeding around the plants potentially painful. Prevent and controlling weed growth can help you save your hands from scratches and your blackberries from weedy competitors.
The Trouble with Weeds
Uncontrolled weed growth can negatively affect your blackberry bush in several different ways. Weeds compete with your bush for soil nutrients, moisture, growing space and light; blackberries require sufficient levels of each to grow vigorously and produce plentiful fruit crops. Weeds often attract insect pests that feed on blackberry blossoms or fruit. Thick weed growth can even reduce air circulation while promoting a damp environment, both of which encourage the growth of fungus or mold.
What Blackberries Like
Proper site preparation helps reduce weed growth while optimizing growing conditions. You should ideally select the growing site about one year before planting your blackberry bush to give you plenty of time to remove all weeds from the area. The University of Florida IFAS Extension recommends keeping a 4- to 6-foot weed-free area around each blackberry plant to promote optimal fruiting. Blackberry bushes prefer sites with good drainage, ample air circulation, full sun and moist soils with pH levels ranging from 5.5 to 6.5. Plant multiple bushes in a row, leaving about 2 feet between them to make it easier for you to weed around the plants.
Placing a layer of organic mulch at least 4 inches thick around your blackberry bush helps prevent the growth of weeds. You can use various natural materials, including wood chips, pine bark or needles, grass clippings and hay, but experts at the University of Kentucky suggest using a wheat straw mulch to promote larger blackberry crops. The Arizona Cooperative Extension website recommends using a black plastic mulch to smother those stubborn, hard-to-control weeds that sprout runners.
You can often maintain good weed control in your home garden by hand-pulling, hoeing or mowing down any unwanted pest plants. Hand-pulling is the safest way to get rid of weeds because blackberry roots grow near the soil's surface and it's very easy to accidentally injure them when cultivating around the bush with a hoe. When removing weeds with a hoe, scrape or dig no more than 2 inches deep to avoid injuring the shrub's roots. Wear long sleeves and gloves when weeding around blackberries.
Some herbicides are preemergent treatments that you spray around planting areas to stop annual weeds from sprouting. The University of Florida IFAS Extension suggests using an isoxaben-based product to prevent the emergence of weeds. Following the instructions on the label, use about 1 cup of herbicide for every 100 square feet of growing space. Irrigate the treated area with at least 1/2 inch of water immediately after application. You can reapply the product after 60 days, if necessary. Postemergence herbicides that contain glyphosate can quickly kill weeds that have already sprouted. After consulting the label for application instructions and safety precautions, mix between 1/2 and 9 ounces of product into 1 gallon of water. Carefully spray the solution right on the unwanted weeds so you don't accidentally get the herbicide on your blackberry bush. Don't allow children or pets to enter the treated area until the herbicides completely dry.