Do You Need to Fertilize Blackberries?

Soil pH and Amendments

• Blackberries grow in soil with a pH between 5.5 and 6.5. Testing determines the pH level of your proposed planting site. Most beds require an amendment of dolomitic lime to bring the soil to the proper pH level, with the amount needed indicated by the test. Organic amendments of compost also help add some nutrition to the bed while improving the quality of the site.

Fertilizing New Plants

• It takes blackberry bushes approximately two years to establish a healthy root system in the bed. Fertilizing during this time further encourages healthy root and plant growth, so the blackberries establish more quickly. A balanced fertilizer, such as 10-10-10 blend, applied in late spring after the plants begin actively growing, supplies enough nutrients for the year. Each plant requires 1/4 lb. fertilizer to have enough nutrients during the establishment years.

Fertilizing Established Plants

• Once established, blackberries aren't as dependent on fertilization but replenishing the nutrients in the soil does help encourage continued plant growth. A balanced fertilizer still provides the necessary nutrient ratio for mature blackberry plants. Applying up to 1/2 lb. fertilizer per plant in summer, after the berry harvest, helps the plant roots remain healthy and keeps the blackberries productive.

Application Method

• The roots of blackberry shrubs grow close to the soil surface, which makes them prone to fertilizer burns. Applying the fertilizer away from the bushes allows the fertilizer to leach out to the root systems as it dilutes in the soil, which prevents burns. Sprinkling fertilizer in a circle 1 foot out from the base of establishing plants ensures the nutrients are close enough for the roots to access but no so close that burning occurs. Established plants have roots that stretch out further from the trunk, so applying fertilizer down the center of the row prevents burns.