In the wild, blueberries grow in mountain forests, beneath the shade of tall trees. This environment has allowed blueberries to adapt to acidic soils without much fertility. If you want to grow blueberries successfully at home, you'll need to provide them with soil conditions that mimic their natural preferences. Blueberries don't require much fertilizer, making them a good candidate for homemade fertilizer blends.
Before you attempt to grow blueberries, you should begin with a soil test to determine the pH, organic-matter content and fertility of the soil. Blueberries require an acidic soil with an optimal pH between 4.5 and 5.1, although they will survive at a slightly higher pH.
Garden centers often sell fertilizers intended for acid-loving plants like blueberries that help to keep the pH low. However, you can lower the pH of your soil, if needed, with elemental sulfur, available at garden and agricultural supply centers. First, determine the number of pH points needed to lower the pH to 4.5. Next, determine your soil texture by taking a pinch of moist soil and trying to stretch it into a ribbon. Clay soils will stretch 2 inches or more, and loams will stretch 1 inch or less. Sandy soils won't stick together at all.
For every pH point above 4.5, add 3/4 lb. of sulfur per 100 square feet for sandy soils. Add 1 1/2 lbs. for a loam and 3 lbs. for clay, mixing the sulfur into the top layer of soil. Allow the sulfur at least 6 months to lower the pH.
In the forests where they grow, decaying leaves and other plant material creates a soil rich in organic matter. Likewise, any homemade fertilizer you make for blueberries should take organic matter into account. Especially if your soil test reveals organic-matter levels below 2 percent, you should add organic materials to your soil.
Sphagnum peat moss, pine sawdust and pine bark are typically recommended as organic matter for blueberries. However, you can also use materials that you have on hand at home. Dry autumn leaves, chopped and worked into the top layer of soil, add organic matter, as do straw, paper shreds and compost.
Blueberries don't require high soil fertility and can be damaged by the application of too much fertilizer. The only nutrient you should expect to add regularly is nitrogen. Coffee grounds and grass clippings are nitrogen sources that you can find or make at home. Sprinkle 5 cups of coffee grounds or a 1-gallon bucket of grass clippings within a 3-foot circle around the plant.
Unless your soil test reveals deficiencies in other nutrients, you likely won't need to apply other nutrients to your blueberries. They will receive small amounts of phosphorus, potassium and trace minerals from the organic matter and nitrogen sources that you add to the soil.
- Purdue University Cooperative Extension Service; Fertilizing Blueberries; Richard A. Hayden; April 2001
- North Carolina Cooperative Extension Service; Growing Blueberries in the Home Garden; Charles M. Mainland, et al.; November 2002
- "Rodale's Ultimate Encyclopedia of Organic Gardening"; Fern Marshall Bradley, et al.; 2009
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