Growing Blueberries in a Home Garden

• Light: Blueberries grow and fruit best in full sun (a minimum of 8 hours per day in summer) but can tolerate some shade. With Maryland’s climate becoming warmer, planting sites that have some afternoon shade may be beneficial.
   
• Soil: Blueberry plants grow grow best in soils with high organic matter content. Six inches of compost should be mixed into the top 8 inches of soil in the planting bed before planting.
   
• Acidity (soil pH): Blueberry is an “acid-loving” plant requiring a soil pH in the 4.5-5.5 range. In most cases, sulfur (either powdered, elemental sulfur, or iron sulfate) will need to be incorporated into the soil prior to planting. Any needed pH adjustments are best done six months before planting. If you have your soil tested, you will receive a recommendation for the amount of sulfur needed to lower the soil pH to a particular level.
  • Clemson’s Soil Acidification Calculator is a tool you can use to determine how much sulfur to apply to lower pH from your current pH, if needed. Application rates are calculated for elemental sulfur and aluminum sulfate.  Do not use aluminum sulfate because blueberries are sensitive to excess aluminum. (It’s okay to apply the sulfur in 1–2 applications.)
     
• Spacing: If grown in rows, plan for 4-5 feet between each blueberry in a row and 6-8 feet between rows. 

Watering

• Avoid drought stress. Blueberry plants have few root hairs (structures that help with absorbing moisture), making them susceptible to drought injury. Their waxy leaves help reduce the loss of water during hot, dry weather, but they may not recover if allowed to wilt
• Monitor for watering needs throughout the year by feeling the soil several inches deep. Water deeply before cold weather sets in if the soil moisture is low. Special mycorrhizal fungi live in and on blueberry plant roots in a symbiotic relationship. The plant provides nutrients for the fungi to grow, and the fungi collects water and minerals in the soil to be used by the plant. Even with this extra help, it’s important to water blueberry plants during dry periods. 
• Focus on watering the root zone. Overhead (sprinkler) irrigation can be used on blueberries, but trickle or drip irrigation is preferred because it conserves moisture and does not wet the foliage. The drip lines (or soaker hoses) can be placed directly under the mulch. Overhead irrigation can help to cool plants and berries during extremely high temperatures. You can also use a hose with a water wand to irrigate under the dripline of each plant whenever rainfall is lacking.

Mulching

• A year-round organic (biodegradable) mulch is especially important for blueberry plants. Mulch with wood chips, pine bark, aged sawdust, or pine needles. Wet the soil before applying mulch.

Fertilizing

• Blueberry plants prefer the ammonium form of nitrogen (N) to the nitrate form. 21-0-0 (ammonium sulfate) is an excellent synthetic fertilizer for blueberries. Fertilizers formulated for “acid-loving” plants are also suitable. Organic fertilizers can be substituted. Avoid fertilizers containing high percentages of nitrates. If potassium is needed, apply it as potassium sulfate rather than potassium chloride.
• Do not fertilize the first year after planting. In the second year, apply 2 ounces of 21-0-0 (ammonium sulfate) per plant during bloom, and the same amount again 3 weeks later. Scatter each fertilizer dose in a ring 12 to 18 inches from the plant.
• Third-year and older plants can have their fertilizer dose increased by 1 ounce per year each year until the sixth year. Then, use 8 ounces total per plant each succeeding year.

The guiding principle behind blueberry pruning is renewal pruning: remove the older, decreasingly-productive canes by cutting them out to force the growth of new canes. Pruning invigorates the plant, forcing vigorous replacement growth from the base of the plant. Renewal pruning is also done with grapes, peaches, and currants. Pruning will also increase fruit size and improve berry quality.

Pruning young blueberries

• Prune back the top ⅓ to ½ of each cane (main branch) immediately after planting. 
• Remove all flower buds and open flowers to save the plant’s energy for new root growth. This helps to ensure good establishment. 

Pruning in seasons 2-5

• In February or March, remove weak, spindly shoots and those that are growing low on the plant near the ground.
• Remove a few of the small branches or twigs in the center of the bush to reduce crowding. If two canes are crossing/rubbing, remove the weaker one.
• Fruits are produced on wood grown the previous season, and the largest berries are produced on moderately vigorous wood (branches 12- to 18 inches in length).

Pruning in seasons 6 and older

• A healthy plant should produce 3 to 5 new canes several feet long each year. Old canes over 1 inch in diameter near the base naturally develop peeling, shredded bark, and stop producing fruit.
• Each spring, select the best two or three new canes to retain and remove some of the oldest canes where they emerge from the crown. Pruning will result in a plant with 12 to 18 canes of varying ages. This is an optimal scenario; many plants will deviate from this ideal.
• Remove the lowest canes and and the weakest center canes as they will produce small, poorly- colored, and late-ripening fruit.
• Overly-long canes with many flower buds may be headed back.
• Failing to remove older branches can cause new canes to be willowy and produce only a few berries at the top.
• Neglected plants with very old canes can be rejuvenated by removing all of the old wood. It will take a few years for the plants to become productive again.

Resource

Pruning Blueberries | North Carolina State University

• Harvest begins in June for early-ripening varieties and may continue through mid-September with late-ripening varieties.
• Berries turn blue 3 to 6 days before they attain maximum sweetness and flavor (depending on weather and cultivar).
• Blueberries do not ripen after picking. Do not pick berries with a reddish tinge at the stem end because they are under-ripe. Berries ready to be picked will detach easily from the pedicel (stem attaching the berry to the branch).
• If possible, harvest berries in the morning after the dew has evaporated. Berries picked in the afternoon will contain field heat, which will reduce storage life.
• A mature highbush blueberry plant will produce 6 to 8 pounds (7 to 9 pints) of fruit per year.

Plant stress: Blueberry leaves naturally turn red and purplish in autumn. Stressors like transplant shock, drought, very cold spring weather, and high summer temperatures can also cause this color change during the growing season.

Iron chlorosis:  Leaves turn pale green to yellow with leaf veins remaining green. Symptoms develop because iron is not available to the plant, even though this element is fairly abundant in most soils. When the symptoms develop early in the spring, the soil pH is usually too alkaline (above pH 6.0). When the symptoms develop during the summer, soil temperatures for these shallow-rooted plants may be too high. If left untreated, chlorosis can slow growth and weaken plants.

If the soil pH is too high, sulfur or iron sulfate can be incorporated into the soil to acidify it so that iron will be more available to plant roots. If the soil is low in organic matter, move mulch to the side and spread 1-2 inches of compost over the root zone, then re-apply the mulch.

Resources for insect pests and diseases:

Pest Management Guide (click Home Fruit) | Virginia Cooperative Extension
UME recommends this guide for Maryland’s home fruit gardeners.

Mummy Berry of Blueberry | Ohio State University

Leaf Diseases of Blueberry | NC State Extension