Maximize the Evergreen Approach to Growing Blueberries
‘Arcadia’, an evergreen southern highbush blueberry variety, produces fruit during the early fresh market window in Florida and can have an extended season. Photo courtesy of University of Florida Blueberry Breeding Program)
In Florida, southern highbush blueberries are grown in two different production systems, deciduous (dormant) and evergreen. The deciduous system is typically used in North and Central Florida. Under this system, blueberry plants are allowed to go dormant and defoliate in late fall and early winter, and each cultivar requires a certain number of hours with a temperature between 35°F and 42°F in order to break dormancy, flower, and produce fruit. In the evergreen system, which is used in South Florida and some areas of Central Florida, varieties that have been developed for this type of production are managed to not go dormant and retain their foliage through the following spring’s harvest. This typically results in an earlier harvest than under the deciduous system, which is an advantage due to higher market prices during that time. Also, this system allows blueberry production to occur in South Florida, where insufficient chilling may prevent successful use of varieties under the deciduous system with higher chilling requirements.
Evergreen Varieties
The University of Florida has released southern highbush blueberry cultivars that are well-adapted to the evergreen system, including ‘Arcadia’, ‘Avanti’, ‘Kestrel’, and ‘Optimus’. These cultivars perform well in warmer winter temperatures, have fruit that matures early, and exhibit good leaf retention.
The cultivar ‘Arcadia’ is a vigorous, high-yielding variety with foliage that is resistant to many leaf diseases, although it has shown susceptibility to the soil-borne disease bacterial wilt. ‘Arcadia’ produces fruit during Florida’s early fresh-market window and can have an extended season.
The cultivar ‘Avanti’ ripens very early, has firm, sweet berries, and above-average yield potential. It is somewhat susceptible to mite damage if they are not controlled.
The cultivar ‘Kestrel’ blooms and ripens very early and has excellent fruit flavor. Fruit detachment force can be somewhat lower than other varieties, at times resulting in some fruit drop during heavy storms.
The cultivar ‘Optimus’ is a very high-yielding variety with good natural leafing and medium-sized, sweet, very firm fruit. It is an excellent choice for machine harvesting.
Management Tips
In addition to using varieties adapted to the evergreen system, certain management practices are required in order to maintain strong, healthy foliage on plants to support earlier fruit production and harvest. These include different fertilization, irrigation, and pest management practices.
With the deciduous system, growers typically stop fertilizing between August and September, both to encourage the plants to go dormant in the fall and to help stimulate flower bud differentiation. Fertilization will generally begin again in January or February. However, when using the evergreen system, many growers may stop fertilizing for around six weeks beginning in September to stimulate floral bud initiation but will begin fertilizing again, often with a somewhat reduced rate (although research is currently lacking for specific fertilizer recommendations for evergreen production in Florida).
Continued fertilization helps keep the foliage healthy and intact. Similarly, it is important to maintain a sufficient amount of irrigation to support a healthy plant canopy. Under the deciduous system, plants do not require the same level of irrigation since they are dormant and become defoliated.
Disease and insect control are also important parts of a successful evergreen production program to keep the foliage healthy and intact and to support early fruit production. Blueberries in Florida typically go through flower bud differentiation during late summer and early fall.
Research has found that if defoliation occurs prior to or during that time, the number of flower buds and resulting fruit yield may decrease. Fungal leaf diseases remain a concern into early fall months, including anthracnose, Phyllosticta, rust, Septoria, and target spot (see University of Florida Electronic Data Information Service (UF EDIS) publication PP348, “Florida Blueberry Leaf Disease Guide” for details). Scouting for these diseases and implementing appropriate management steps is critical for successful evergreen production since it will help minimize the incidence and severity of disease and possible defoliation.
Damaging insect and mite pests must also be controlled during this time. Chilli thrips and southern red mites can cause significant damage to foliage if not controlled and can lead to defoliation in severe cases. As with leaf disease, scouting and putting applicable controls in place are essential to maintaining a healthy plant canopy.
Additional discussions of the evergreen production system can be found in UF EDIS publication HS1362, “Evergreen Production System for Southern Highbush Blueberries in Florida.”
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