In The Garden Now: Blueberries
By Les Harrison, UF/IFAS Wakulla County Extension Director and Gohar Umar, FAMU Horticulture Extension Agent
The cold temperatures in Wakulla County’s latest winter were few and relatively mild. The near triple digit readings this week has had many looking back fondly to the irregular, but comparably pleasant winter.
Blueberries, like some other fruit trees grown locally, need a certain amount of time at less than 45 degrees temperature. With insufﬁcient winter chilling most of these fruit bearing plants do not ﬂower.
Fortunately, low-chill cultivars have been developed by plant breeders at University of Florida and elsewhere. A wide variety of named blueberry cultivars of varying size, color and taste are available with some fruiting much earlier than others.
There are two main types of blueberries which grow in Florida, the rabbit-eye and southern highbush. In Wakulla County the rabbit-eye varieties will perform much better as they flower in late March and the ﬂowers will not be affected by most freezing or frosty weather.
Southern Highbush on the other hand will grow better to south of Ocala, but can be grown in North Florida as well with freeze protection. Freeze protection is provided with overhead sprinklers which get turned on when the plants are flowering or fruiting, and the temperature falls below 30 degrees.
Therefore it is very important when selecting cultivars to choose those which will blend with the local environment and weather conditions. Literature and advice on best management practices and recommended cultivars is available at the UF/IFAS Wakulla Extension Office and on the Electronic Date Information System (EDIS) site.
When establishing a blueberry patch, it is best to plant in fall or winter. Two foot tall plants with well established root system are recommended. Blueberries grow best in lower pH acidic soils of 4.0 to 5.5.
Typical Wakulla County soils have higher pH reading and it is recommended to use pine bark compost as it has low pH. Additionally pine straw can be used as mulch which in turns breakdown and lowers the pH of soil.
The blueberries should be planted deep as they were grown in their nursery pots. Dig the hole twice as size of the root ball or more to accommodate the pine bark compost and roots.
The plant should be pruned to take out the weak and overcrowded branches no more than one third of the total plant size. This will inhibit the plant from fruiting and concentrate more on vegetative growth.
Blueberry plants are pruned to inhibit the growth of dense, twiggy, and nonproductive canes. Pruning the plants at two years and onward is basically a matter of removing and thinning the canes to decrease the plant height.
Once the plant is fully established in four to ﬁve years, it is recommended to prune one to three year old canes no more the 1/4th of the plant canopy. The branches older than three or four years get removed resulting in rejuvenation of the plant year after year.
Fertilization is very important in all plants. For blueberries use one ounce the first year, two ounces the second year and three ounces the third year. Spread evenly three feet around the plant, starting in April through August.
Application every other month is recommended. Use the 12-4-8 analysis with the 2 percent magnesium blend which is available at most local garden centers.