Information About Acid Soil for Blackberries

Using Lime to Raise the pH Level

• Dolomitic lime is the preferred choice for raising the pH level of soil. It is made of magnesium carbonate and adds magnesium, necessary for good plant growth, to the soil. Avoid quicklime or hydrated lime, which work quickly, but are caustic and may burn the blackberry plants. The general rule of thumb is to add 5 to 10 lbs. of lime to the soil per 100 square feet to raise the pH one scale interval. Add more if you have heavy clay soils, less if you have sandy soils. For example, to raise the pH from 5.5 to 6.5, add 4 1/2 lbs. to sandy soils, 7 1/2 lbs. to loam soils and 10 lbs. to clay soils. Spread the lime over the surface of the soil and till it to a depth of 6 inches in the fall, or at least three months before planting the blackberries.

Other Amendments

• Add other amendments, such as well-rotted manure or compost, to the soil when you add the lime. Add 2 cubic yards manure or compost per 100 square feet of soil to improve drainage and aeration and add nutrients. Blackberries, like all berry fruits, need rich, fertile soil to produce high quality fruits. After planting, fertilize the plants with 1/2 cup 12-12-12 fertilizer per plant. Make two more fertilizer applications, one and two months from the first application.

Growing Conditions

• Blackberries grow in partial shade, but they fruit better in full sun. They don't tolerate winter cold. Plant raspberries instead if you live north of U.S. Department of Agriculture plant hardiness zone 6. Blackberries need at least 1 inch of water weekly during the summer. Provide supplemental water during dry conditions. Mulch blackberries with untreated grass clippings, straw or wood chips to conserve moisture and reduce weed growth. Pull weeds carefully by hand or shallow cultivation to avoid damaging shallow roots. Prune blackberries each fall or winter to remove dead and diseased growth and tangled branches. Most blackberries benefit from a trellising system.

Harvest and Uses

• Harvest blackberries when they lose their glossy appearance and taste sweet. Eat blackberries fresh or freeze them. Blackberries have a slightly acidic taste, and many people prefer them baked in pies and cobblers rather than fresh. Make them into jams or thin syrups for ice cream and pancakes.