For The Answer
By Calvin Finch, Conservation Director, SAWS, and Horticulturist
Blueberries in Containers
Gardeners are always looking for new plants to try. If you are willing to follow a few guidelines you can grow rabbiteye blueberries in a container in San Antonio. Jerry Parsons and Larry Stein, horticulturists with Texas Cooperative Extension have developed the plan and area nurseries have all the material you need including the Tifblue blueberry plants for about $13. If you follow the directions in this article, after 2 or 3 years, you can harvest about 15 lbs of delicious, nutritious berries every year. Even if the rabbiteye did not produce berries, the plants make an attractive container plant for your patio.
Blueberries require acid soil. A pH of 4.0 to 5.0 is ideal. They will not survive in our alkaline soils so we must use containers. A half whiskey barrel is the ideal size. In addition to the acidic soil, the blueberry requires a well-drained environment, plenty of moisture and full sun.
Achieve the acidity you need by using a peat based potting soil and sphagnum peat. A 50-50 mix works well. Water when the soil is dry to the touch. To maintain the acid conditions use rainwater, air conditioning condensate or acidified water (1 tablespoon vinegar per gallon) to irrigate. If you use a whiskey barrel, drainage holes will have to be drilled. Drill 8 or 10 half inch holes spread evenly over the bottom of the container.
Drs Parsons and Stein identified the Tifblue blueberry as the best choice for container culture in San Antonio. The plant will reach about 7 feet tall in a whiskey barrel and produce berries over a 6-week period May to July. Despite claims to the contrary in most resource books, Parsons and Stein say that a pollinator is not required.
The fruits are large and light blue. The bush is vigorous and very productive. Tifblue is more cold hardy than most rabbiteye blueberries varieties and receives adequate chilling (cold temperatures) to fruit as far south as Pleasanton, Texas. Tifblue rabbiteye blueberries require little pruning. Lower limbs can be thinned out to keep the fruit from touching the soil. Branches full of berries can be heavy. Excessively vigorous upright shoots can be thinned out several feet from the ground to keep the center of the bush open and to keep the bearing surface within reach. Spindly, weak, or dead branches should be thinned out annually during the dormant season. Don't pick the berries until they are fully ripe; otherwise the fruit will be bitter. Once the berries begin to ripen they should be picked every 3 to 5 days. Birds love blueberries as much as gardeners but the bush is easy to cover with bird netting.
Fertilize at planting with Osmocote and then once a month with a soluble fertilizer. Miracid is a good choice because it helps keep the container acidic. Never use granular lawn fertilizer for blueberries because the plants do not tolerate salting. Even soluble fertilizer and Osmocote can cause a problem if drainage isn’t adequate. The water should move quickly out the drainage holes and never cause a soggy condition. On the other hand, rabbiteye blueberries are not a xeriscape plant. The soil should not be allowed to dry out.
Mulch will help keep the blueberries from drying out. Any organic mulch except manures or manure-based compost will work. Manures are alkaline and salty. Sphagnum peat moss is the best mulch.
Several San Antonio area nurseries are featuring Tifblue blueberry plants, whiskey barrels, sphagnum peat moss and peat based potting soil now.