How to Fertilize Blueberry Bushes

A few blueberries hanging off of a branch.
What You'll Need
Organic matter
Soil testing kit
Sulfur or aluminum sulfate
Dolomitic lime
Peat moss
Ammonium sulfate
High-nitrogen fertilizer

Blueberry bushes aren't the easiest plants to grow, but if soil acidity and drainage conditions are right then the plants should produce abundant fruit. A good fertilizing schedule can also help the plant, but you have to be careful about what you use and how you use it to maintain the good health of your bushes.

Tip: Mulching goes hand in hand with fertilizing and is also very important for blueberry bushes. Mulch your bushes after planting and fertilizing with a three to five inch layer of pine bark or a two to three inch layer for sawdust. This will help to retain moisture in the soil and reduce soil temperature. Add mulch annually to maintain the layer depth.

Step 1 – Start Preparations Early

The best time to start fertilizing blueberry bushes is a year or two before you plant them. Working organic matter into the soil, continued weeding and careful correction of the pH balance can be done over time and once the conditions are right, planting can begin. An ideal site for blueberries will be in full-sun and have well-drained, low pH (4 to 5) soil that has high organic matter content.

Step 2 – Measure pH Level

Buy a soil testing kit from at your garden center, or, if not available, call your County Extension Office (the number is in the government listings in your phone book) for soil-testing information. The pH should be between 4.5 and 5.1, though it can be a little higher if other conditions are favorable. To lower the pH, sulfur or aluminum sulfate can be added to the soil. These additives need to be mixed thoroughly throughout the upper layer to be effective. For a home garden, about 3/4 of a pound of elemental sulfur per 100 square feet is a good measurement. If the soil is very loamy, it could take up to two pounds, and clay soil will probably need three pounds per 100 square feet. It could take six months or longer to show improvement.

If the pH is very high, the process to lower it can prove costly and time-consuming, so if you haven't already planted blueberry bushes, you should find another spot with a better pH level. If you've already planted, you may consider replanting, especially if lime is present because the pH will probably never stay within the desired range.
If the soil is too acidic with a low pH, dolomitic lime can be added to bring the level up, but make sure to recheck it before planting.

Step 3 – Check the Density of the Soil

The soil will be fine if its heavier and denser as long as the pH level is correct. Otherwise blueberry bushes will do best in a soil that's rich with organic matter, like a soil that contains mixture of sand and peat. It has to be a soil that drains well, as blueberry plants can easily be damaged by water standing around the roots. To amend your soil, use one part sand and one part peat moss to two parts soil. Dig the sand and peat as deep into the soil as possible, preferably one foot deep or deeper.

Step 4 – Maintain the pH Level

In areas where you've had to make pH corrections because of alkaline soil, add ammonium sulfate after planting to increase nitrogen and keep the level correct.

Step 5 – Develop a Fertilizer Schedule

As long as you maintain the pH balance of the soil, a complete fertilizer should be sufficient. A high acid fertilizer, like azalea or rhododendron fertilizer, is ideal. In some areas, special blueberry fertilizers can actually be obtained instead.

Fertilize young blueberry plants individually, and for the first time a month after planting. Work high-nitrogen, non-nitrate fertilizer into the top six inches of the soil, taking care to keep it away from the stem and avoiding direct contact with the roots. Nitrogen is very important for blueberries, but other chemicals in nitrate form can be toxic to them. Adult plants can be fertilized with an applicator, if desired, and the amount of nitrogen fertilizer can be increased to five ounces per plant. Fertilize only when the plants are dry, to avoid particles sticking to the plants and doing damage. Doing so in the early spring before foliage appears is ideal. It can be applied again later in the season when the berries begin to form.

In an organic garden, fertilizers such as blood meal and cottonseed meal work well. Avoid using fresh manure, and always water well after fertilizing!

If you follow along with these steps, your blueberry bushes should lead long and healthy lives, producing plenty of fruit for your enjoyment.