Blueberry bushes (Vaccinium spp.) are wonderful to have in the backyard for a handy, healthy snack for the kids or for cooking tasty blueberry muffins and pancakes. The berries can also be frozen to enjoy in the off season. They are hardy in U.S. Department of Agriculture plant hardiness zones 3 to 9, depending on the variety. Good fertilizer is necessary for healthy, productive blueberry bushes. You will need fertilizer that contains the most important nutrients and soil conditions that will allow the blueberry bushes to absorb these nutrients.
Keep it Green
Nitrogen and potassium or potash, listed on fertilizer bags as the first and third numbers, are the most important nutrients for basic shrub growth. They are macronutrients. Nitrogen is required for the shrub to grow tall with lush, green leaves. Potassium is important for the general health of the shrub. It improves the shrub’s resistance to diseases and insect attacks as well as drought conditions and cold winter temperatures. Magnesium and calcium are macronutrients that are also important for healthy shrub stem and leaf growth. Iron, manganese and zinc are micronutrients that are important for good chlorophyll production, which makes the leaves a nice, healthy green and better able to conduct photosynthesis. They are required for vigorous shrub growth.
No Mushy Blueberries
Phosphorous is the most important macronutrient for healthy flowering and fruit production. It is the second number listed on fertilizer bags. Phosphorous is also necessary for strong, healthy root growth. Calcium is another macronutrient that is important for healthy stem and leaf growth as well as good, firm blueberry production. Boron is a micronutrient that is important for healthy bud break and blueberry size.
All Fertilizers are Not the Same
The type of nitrogen in a fertilizer is very important for blueberries, notes the Virginia Cooperative Extension. Use fertilizer with nitrogen in ammonium form, which may be listed on the bag as NH4 +. A complete 7-7-7 or 10-10-10 fertilizer with ammonium sulfate or potassium sulfate should be all the blueberry bush needs to grow and produce berries. Apply the fertilizer in early spring and again in late spring for the first two years. Give each shrub 1/8 cup each time during the first year and 1/4 cup each time in the second year. From the third year on, give each shrub 1/4 to 1 1/2 cups of fertilizer, depending on how quickly they are growing. Ideally, the soil should be tested for nutrient levels before deciding on a fertilizer. Excesses in many nutrients can be very harmful and as Floridata states, blueberries are easily killed by too much fertilizer. Boron, for example, should not be applied without a soil test as excess levels are toxic to blueberries. It can burn leaf edges and young shoot tips, notes Oregon State University. Excessive nitrogen or the wrong type of nitrogen will burn the roots.
Don’t Tease the Blueberries
Soil pH is as important to blueberries as nutrients. The soil pH must be between 4.5 and 5.4. If the pH is lower or higher, the blueberry bushes may not be able to absorb some nutrients like iron and zinc, even if they are present in the soil. This will cause the leaves to develop chlorosis and turn yellow. Test the soil pH six months to one year before planting the blueberry bushes. It can take that long to adjust the soil pH. Mix sulfur into the soil to lower the pH or lime to raise the pH. The amount required will depend on the soil type and how much the pH needs to be adjusted.