Skip to main content

Smart Gardening 2020: How to Prepare Your Soil for Planting Blueberries

Blueberries ripening. Photo: Annie Klodd.
Did you know? Blueberries are unique from many common garden plants, because they require acidic soil in order to grow and produce fruit. That means that before planting new blueberry plants, you must check your soil pH and then amend it prior to planting your blueberries. This article outlines how to do that.

Blueberry soil requirements

Blueberries require the soil to have a pH between 4.3 to 5.5 pH. This is unique, because most fruit and vegetable plants do best in a relatively neutral pH soil between about 6.5-7.5. Growing blueberries between 6.5-7.5 would cause them to have slow, weak growth, yellowish leaves, and little to no fruit.

Reducing the pH prior to planting and keeping it low for the lifespan of the plants, will help ensure strong fruit yields and healthy plants. The pH is amended by adding sulfur to the soil in the form of sphagnum peat moss, elemental sulfur, or another widely available sulfur amendment found at garden stores.

How to check your soil pH

The pH of the soil must be determined before adjusting the pH for blueberries. The original pH of your soil, along with your soil type, will determine how much amendment should be applied.

Soil pH is determined by simply taking a soil sample in the area where you want to plant blueberries, and submitting the sample to the University of Minnesota soil testing lab or a similar lab. This is easy, inexpensive, and does not take long to do. Plan to do this as soon as the soil is workable in the spring. Instructions for taking and submitting a soil sample are here: Soil Testing - A Sure Sign of Spring!

After submitting a soil sample to the lab for testing, you will receive back the results in the mail or over email. The results will list the pH of your soil sample among other valuable information like soil nutrients, soil texture, and the percentage of organic matter in your soil (OM%). 

If your soil is above 5.5 pH, which it most likely is, then it will need to be amended before planting blueberries. Generally, the higher the pH, the more sulfur amendment that must be added.

The estimated soil texture and the organic matter % listed on your soil test report will also help you determine how much amendment to apply. Higher organic matter soils require larger amounts of sulfur to change the pH.

How to Amend your soil pH

Using Sulfur 

It is best to amend the pH the fall before planting, because it takes several months for the pH to change after sulfur is applied. To do this, add elemental sulfur to the soil in the planting area. 

Elemental sulfur is widely available in garden stores. It may be marketed as soil acidifier or as soil sulfur/sulphur. The amount of sulfur to apply depends on the soil pH and soil type. To determine how much to apply, refer to page 2 of this article by Oregon State University. 

Using Sphagnum Peat Moss

However, if you plan to plant this spring and have not amended your soil yet, the best option at this point is to add an acidic growing medium like sphagnum peat to your planting area. This is a suitable method if the original pH is between 5.5-7.0. To do this, add 4-6 inches of sphagnum peat to the top 6-8 inches of the soil in the area where the blueberries will be planted. 

Please note that this is a significant amount of material, and the cost of it should be considered when planning out a blueberry patch. Labor will also be needed to dig out the row where you plan to plant, and to use a shovel or rototiller to evenly incorporate the peat into the soil.

Amend the soil in the entire planting area, not just in the planting holes. The roots will expand outward, so amending the soil in a 2-3 foot wide strip is important to ensure the roots have access to acidic soil.

A soil with a pH at the top of that range (closer to 7.0) will require more peat (5-6 inches), while a pH at the bottom of that range (5.5-6) requires less peat (4-5 inches). 

These are general guidelines, and every soil is different. Therefore, submit another soil sample from the planting area about 6 months after planting. This will determine whether the soil has been amended down to the correct pH range, or of more amendment is needed.

Do not use coffee grounds as a pH amendment

Despite some online claims, coffee grounds are not necessarily acidic and should not be relied upon as a pH amendment for blueberries. According to this well-informed analysis by Linda Chalker-Scott at Washington State University, not all coffee grounds are acidic. Even if the coffee grounds you use happen to be acidic, it would probably require a massive amount of them to change the pH of the soil, and the results would not be reliable.

Planting Blueberries and Choosing Varieties

Information on choosing blueberry varieties, and planting and caring for the plants, can be found on the University of Minnesota Extension website at: Growing Blueberries in the Home Garden.

General tips for planning out a blueberry planting:

  1. Plant blueberries at least 5 feet apart. This may appear far at first, but the plants will grow to fill in the space. If planting multiple rows, rows should be spaced at least 6 feet apart. Planting rows any closer than 6 feet will make it difficult to walk between rows and access the fruit during harvest. Planting too close also creates competition between the plants, and increases the risk of disease and insect damage.
  2. Expect to harvest between 6-8 pounds of fruit per plant each year, starting 3-4 years after planting.
  3. Order varieties from a reputable fruit nursery, to help ensure that the seedlings are disease-free. Do not transplant blueberries from one garden to another, which spreads plant diseases.
  4. Select varieties that are well-suited for our Minnesota climate (USDA Hardiness Zones 3 and  A number of high quality varieties are available for Minnesota, and are listed here. 
  5. Plan ahead when amending the soil. Soil pH takes several months to adjust after it is amended. Therefore, amending the soil the fall before planting is best if possible.
  6. Avoid planting blueberries against a wall, as the wall may create extra heat that can damage the foliage. Do not plant blueberries in shade.

Author: Annie Klodd, Extension Educator - Fruit and Vegetable Production

Print Friendly and PDF