By Dr. Lily Calderwood, Ph.D., UMaine Extension Wild Blueberry Specialist, and Mara Scallon, Research Assistant, Lowbush Blueberry Research and Extension Program, University of Maine.
Establishing a new wild blueberry patch
Soil
It’s important to plant wild blueberries in well-drained soils, like sandy soils. Do not plant wild blueberries in clay soils. Identify your soil pH by taking a soil sample.
Apply sulfur to decrease the soil pH to 4.0 – 4.5; see soil pH Management for recommendations on applying sulfur. Note that sulfur should not be applied when the ground is frozen or saturated or when your wild blueberry leaves are wet as you could burn the wild blueberry leaves.
To sample your soil, pick up a soil sample box and form from your local University of Maine Cooperative Extension County Office, or from the Analytical Lab and Maine Soil Testing Service. Call 207-581-3591. Some garden centers may carry them as well.
Using a trowel or small shovel and bucket, head to the location you’d like to plant wild blueberries and gather multiple samples of soil by digging a few small holes 3 to 6 inches deep. Repeat 10 times minimum, then mix these soil samples together in a bucket and use the resulting mixture to fill a soil sample box. Mail the box and soil sample form to the Maine Soil Testing Lab in Orono with payment. Please send a check or money order to cover the cost of the analysis. For additional information on testing your soil, see Testing Your Soil.
Transplanting
When buying blueberry sod be sure to choose a reputable nursery. Sod usually comes in 1-foot-by-1-foot, 3-inch thick blocks.
Transplant the sod in the desired location. Wild blueberries can be planted as separate plants, in rows, or mixed in with other plants. Just like rhododendrons and azaleas, wild blueberries need full sunlight to grow best. You may need to prune nearby plants to maximize wild blueberries’ exposure to sunlight.
For the first two years of growth, you want wild blueberries to put their energy into growing strong roots, so you must pinch off all blossoms for those first two seasons. Painful as this is to do, it will improve the long-term health of wild blueberries substantially.
Mulch
Apply softwood mulch among sod pieces and in between blueberry stems. This adds organic matter and holds moisture, aiding in wild blueberries’ root development. Softwood mulch is a good choice because it is already a lower pH material and it is readily available in Maine.
Water
Water or irrigate in the first two years so wild blueberries can establish well in a dry season. Wild blueberries need one inch of water per week. If watering, don’t provide this water all at once — space it out over the course of the week. If there is adequate rainfall, there is no need to add supplemental water as this can cause disease.
Encouraging an existing wild blueberry patch
Mow the wild blueberry patch every other fall (October through November) to 1.5-inch height. To mow, you can use a lawnmower, power trimmer, or flail mower on the lowest setting. Don’t worry, 75 percent of the plant is underground so you will not hurt the plants. Wild blueberries need to be mowed in order to produce berries in the quantities we want them to.
If you want to produce berries every single year, you’ll need to develop a two-year production cycle. Split your patch in half (approximately) and mow one half of the patch at the end of the season (in October through November), using a lawnmower, electric trimmer, or flail mower. Leave the other half of the patch unmowed. In the spring, you will see that your mowed patch begins to grow stems and buds and as the season progresses, the stems will grow taller but you will not see any berries. This is known as the “prune year” and the goal is vegetative growth for next year’s berry harvest. The side that was not mowed will produce berries. During the fall after picking the berries, mow this side to produce berries in two years. In short, you will mow half of your patch every year, alternating sides. Berries will be produced every year but on alternating patches.
Burning blueberry plants is another way of pruning the plant, however, this is not recommended for homeowners due to safety reasons.
Water
Wild blueberries need approximately 1 inch of water per week in both the prune and crop years. Ensure your plants are receiving enough water and irrigate as needed.
Manage weeds
Maintaining a soil pH between 4.0 and 4.5 reduces competition from grasses and broadleaf weeds. For more information about applying sulfur to maintain acidic soil pH see the wild blueberry fact sheet on Weeds. For woody tree saplings (e.g. birch, willow, alder) and ferns (e.g. sweet, bracken), cutting is the best management option. Cut these saplings and ferns to the ground three times each year. The goal is to let the plant put energy into above-ground vegetative growth and then cut it away. Cut the undesired plant in early summer when it has fully leafed out, let the plant grow back again, cut it again, and repeat until the plant stops growing.
General best practices
Encourage pollinators!
Wild blueberries are pollinated by a range of insect species including many native bee species and managed honey bees. Entice pollinators to come to your wild blueberries, as opposed to other flowering plants, by planting pollinator-friendly plants that bloom throughout the season. Consider how your use of certain pesticides might adversely impact pollinator populations. For more information see Bulletin #7153, Understanding Native Bees, the Great Pollinators: Enhancing Their Habitat in Maine.
Sunlight
Wild blueberries grow best in full sunlight. If other plants are shading your wild blueberries, you may need to prune or move those plants. Wild blueberry stems will tilt towards the sun when they do not have enough light.
Fertilizer
Keep in mind, fertilizers can feed weeds just as much as wild blueberries so fertilizing is not always needed. Conventional fertilizers for acidic plants contain soluble ammonium sulfate, which allows nutrients to be taken up in the acidic wild blueberry soils. Organic gardeners will want to use products for plants requiring acidic conditions such as those marketed for blueberry and rhododendron.
Troubleshooting
If the plants are not growing or bearing well, start by looking at the following:
- Soils: are they acidic (4.0 – 4.5 pH) and well-drained?
- Sunlight: is there enough?
- Water: is there enough?
Reprinted with permission from University of Maine Cooperative Extension, bulletin #2073, Growing Wild Blueberries in the Home Garden extension.umaine.edu/publications/2073e.