Blackberry, a member of the Rosaceae family, is a temperate-loving plant. Varieties can be either erect bushes or trailing with long, sweeping canes. Wild varieties have thorns, while several hybridized varieties are thornless. Regardless of these variations, soil requirements for blackberry plants are consistent.
Soil pH is a rating of acidity or alkalinity of soil. Blackberries grow in a range of pH levels but perform best when the pH level is between 5.2 and 6.5. A soil test will reveal the current pH of your soil. Once the value is known, add soil amendments to alter the pH. Lime will raise the pH, while sulphur lowers it. Add the amendments at least one year prior to planting blackberries.
Blackberries are adaptable to many soil types, which explains why wild varieties spring up in weed-like fashion in many areas. For the best fruit production however, a sandy loam type soil is ideal. High organic matter content is also beneficial. It promotes loose soil and allows the roots to spread to reach water and nutrients.
Blackberries are one of the later-harvested of the small fruit crops, coming in much later than strawberries or blueberries. As a result, they require more soil moisture at a time when summer’s heat is drying out the soil. Maintain moist soil conditions with frequent, deep watering and the use of mulch to retain moisture. Avoid conditions where blackberries are in standing water, however.
A soil test from your local extension office will reveal any soil nutrient deficiencies. Potassium, magnesium, calcium and boron are commonly needed nutrients for most berry crops including blackberries. These should be worked into tilled soil prior to planting as it is much more difficult to get them down into the soil once plants are established.
Other Soil Preparations
If pH adjustments or nutrient amendments are needed, they are normally added a year before planting blackberries. During that year it is also important to keep weeds to a minimum so as not to strip the nutrients from the soil and so new blackberry plantings do not have to compete with established weed roots. The planting of a cover crop can help with this. Plant a seed crop such as as rye, oats or buckwheat, but plow it under before it goes to seed. This adds organic matter to the soil, keeps soil from becoming compacted and increases nitrogen levels.