Windbreak Design and Management
A proper plan for a windbreak around citrus groves as a management tool for canker protection and reduction of windscar should involve first developing answers to these questions:
- What are your expectations for a windbreak?
- What varieties should be protected?
- What groves, blocks, etc., should be protected?
- For a living windbreak, what plant species are best?
- For a living windbreak, what design is best?
- Is an artificial windbreak the best option or a combination of living and artificial windbreaks?
- For a living windbreak, how many plants will be required and where can they be purchased?
- For a living windbreak, what cultural or management requirements will be needed, if any, for rapid and maximum windbreak establishment and function?
- If I plan sufficiently in advance, can a cost-share be obtained through the NRCS EQIP program?
To help answer these and other questions, information and recommendations are provided in a Question and Answer format. Note that this information is based on international windbreak experience and limited formal experience in Florida. However, the plant species identified and the accompanying information are from Florida.
Q. What are your expectations for a windbreak?
A. Windbreaks will be a major part of a disease management strategy along with resistant varieties and chemicals. Some Florida experience has shown reductions in windscar incidence, a reasonable expectation. Living windbreaks do not generally establish rapidly, but the windbreak species will probably keep pace, if not exceed, the growth of newly planted citrus trees. The exceptions are Eucalyptus, bamboo, and Silk oak which develop quite rapidly. Artificial windbreaks function essentially instantaneous, but are relatively expensive.
Will living or artificial windbreaks withstand hurricanes and other severe weather events? There is considerable evidence to suggest the answer is YES, but the evidence is not consistent nor is the answer predictable without additional experience.
Q. What varieties should be protected from diseases and wind damage?
A. All fruit grown for the fresh market are likely to benefit from reductions in windscar provided by windbreaks. Protecting grapefruit grown for fresh or juice would be particularly important because of its known susceptibility to canker. Likewise, early oranges will benefit, too. It is questionable whether other oranges grown for juice need windbreaks.
Q. What groves, blocks, or other units should be protected?
A. There are three simple rules that dictate how to divide your land into windbreak units:
1. Windbreak height dictates the degree of protection at a ratio of about 1:10, i.e., for every unit of height (H), lateral protection is 10 (H). Thus, a 40-foot tall plant will calm winds about 400 feet into the grove.
2. Your knowledge of the expected (H) for any living windbreak species growing in the local area is very important.
3. In general, windbreak units should be about 10 to 20 acres in size for adequate protection based on the observations in other citrus industries. Size is limited by the height expected for the plant species selected, or the practical limits imposed by cost and other engineering factors for artificial windbreaks.
An appropriate-sized windbreak unit is defined by function, but with adequate consideration for cost, establishment, and maintenance. It makes little sense to plant or erect a windbreak if it is underdesigned.
A Ridge Example. If your grove is located on a typical Ridge Entisol, like Candler sand, you may notice that nearby mature sand and slash pine trees are probably 30 to 50 feet tall. Using 40 feet for (H), the lateral protection expected would be 400 feet which means the windbreaks rows could be spaced 800 feet apart. A square 10 acres is 660 x 660 feet, thus, planting windbreaks to surround the block should provide more than adequate protection.
A Flatwoods Example. The aerial photo below is of a typical Indian River grove. As with the Ridge example, local experience with native plants and their mature (H) suggests that 10- or 20-acre windbreak units are practical.
Q. For a living windbreak, what plant species are best?
A. Current recommendations are given in Plant Species tables. The plants are divided into three groups:
FOUNDATION - species that could be planted by themselves in single or multiple rows or be the upper story plant in a multi-species windbreak.
FOUNDATION PARTNERS – species that are best used as the lower story in combination with one of the Foundation species.
OTHER – species for which there is virtually no information about their usefulness in a windbreak, but their published characteristics and field observations suggest potential for that purpose.
In the tables is information regarding expected performance, descriptions of the major attributes and weaknesses, and links to related literature and other details to aid in evaluating the choices.
Note that just studying the tables may not provide sufficient information to make the best decisions. Because the performance in windbreaks of many of the plant species is not well known, or known at all, additional time spent reading some of the literature provided in this website is recommended.
Q. For a living windbreak, what design is best?
A. For any grove whether it is be planted or is already established, you must determine the composition, spacing, and location of the windbreak so that it functions properly, but allows for machinery movement and other grove operations once the size of the protected unit has been decided. Do that before you plant!
The composition of the windbreak, i.e., the plant(s) selected, their arrangement and spacing, is critical. The composition determines how rapidly a functioning windbreak will be established, the degree of maintenance required, if any, and the degree of wind reduction. Composition also involves deciding whether to plant one species, or a combination of species, in a single row or in multiple rows. For example, windbreaks around Ridge citrus groves have been planted with either a single-row combination of slash pine and red cedar or in a multiple row arrangement.
The goal in selecting the plants and their spacing is to achieve about 60% density, i.e., allow about 40% of the wind to pass through. There are no established and tested rules to determine how to achieve 60% density. The value of familiarizing yourself with the young and mature characteristics of the species selected by studying any local native stands of the plants, contacting local botanists and foresters or others familiar with plants in uncultured settings cannot be over-emphasized.
Ridge. On the Ridge, a minimum of 25 feet between the windbreak and the edges (i.e., ends and sides of rows) of the planted area is generally adequate for equipment movement and to allow for canopy development of the windbreak plant without crowding the drive middle or adjacent citrus trees. Plant species: Only Eucalyptus and bamboo are fast growing among the choices currently available. Eucalyptus is suitable for use by itself as a perimeter and/or internal windbreak and can be planted in single or multiple rows. Bamboo is cold hardy, relatively easy to establish, but not readily available and the plants are expensive. Nevertheless, it merits some trial on both the Ridge and in the flatwoods. Consideration should also be given to a single-row combination of Eucalyptus (as the upper story species) and a less vigorous bamboo selection such as Bambusa multiplex as the lower story. With that combination, the spacing between Eucalyptus plants could be increased.
Flatwoods. In the flatwoods, the same basic considerations apply for windbreak design and location. However, in typical bedded groves, water conveyances such as canals and ditches impose additional restrictions especially in established groves. To plant a windbreak along an internal waterway in an established grove may require removing trees from the ends of rows. Also, only one side of the waterway can likely be planted so that ditch maintenance can continue. Plant species: Eucalyptus is an option as a stand-alone species or, where perimeter space would allow, in multiple rows particularly if the intention was to periodically harvest some of the trees and allow the stumps to coppice. That is one strategy that might generate an income and would at least provide for good windbreak coverage with one species. Also, given the limited space available along internal waterways, Eucalyptus could be an excellent choice because the plant will anchor well along ditch banks and its profile is narrow, thus lateral canopy development would not be a problem. Another option to use Eucalyptus where space is limited would be to plant a single row of trees, but closely spaced (3 to 4 feet apart). The management of this single row would be to eventually cut off every other tree and let it coppice. By using this approach, there would always be a tall upper story of trees and a shorter, lower story of trees that provided good windbreak function at all heights.
Southern slash pine (do not use sand pine) would be suitable for an upper story with red cedar or other species as the lower story. However, slash pine does not perform well in alkaline soils, so avoid using them in Chobee, Floridana, Manatee soil series because they usually have calcareous subsoil and in Bradenton/Parkwood, Hilolo/Winder, Pople, Boca, and Hallandale soil series because they always have calcareous subsoil.
Q. Can I avoid planting a windbreak by using the outside rows of my grove?
A. It has been suggested that the perimeter trees and rows of a block be grown on a vigorous rootstock or simply allowed to grow taller than the interior trees. That approach would save money, and anecdotal evidence indicates that the edges of a block are more likely to have canker infections than further into the block. However, such a plan is unlikely to work well because the citrus trees expected to function as windbreak are susceptible to both bacterial disease, canker and greening, and may help spread the diseases. Also, they may not grow tall enough to provide maximum benefit as a windbreak.
Q. Is an artificial windbreak the best option or a combination of living and artificial windbreaks?
A. There are some obvious differences between artificial and living windbreaks. Artificial windbreaks are likely to more expensive, but they are functional as soon as they are erected. Their sturdiness in a major storm like a hurricane is unproven.
Very limited formal experience exists in Florida citrus operations with windbreaks. Most experience is among Indian River growers with fresh fruit operations who used species of Casuarina (Australian pine) and, to some extent, pine and red cedar trees.
Living windbreaks offer the advantage over artificial windbreaks of being less expensive to establish, but they require a longer time to become functional. However, that difference in time can be minimized by planting the most rapid-growing plant species and possibly beginning with fast-growing temporary windbreaks such as sugarcane to protect newly planted citrus trees.
There may be circumstances in which using a combination of artificial and living windbreak would make sense. For example, most existing groves offer primarily constraints to retrofit with windbreaks because of grove space limitations. Artificial windbreaks might be the best solution to space issues at least in internal locations with living windbreaks reserved for perimeter locations where there is often more space available.
Q. For a living windbreak, how many plants will be required and where can they be purchased?
A. The number of plants needed is determined by the lineal distance, spacing between plants, and the number of rows. For example, in the flatwoods illustration above:
- 4620 feet is the lineal distance around 20 acres plus the distance across the middle that separates the 20 acres into two 10-acre units.
- 770 trees are required for that distance if a single-row windbreak is planted with trees 6 feet apart.
- 1,555 plants for trees planted at 4 feet.
Q. If I establish windbreaks around my entire grove will the risk of cold damage be increased?
A. Possibly. We expect that in a windy, advective freeze, trees protected by windbreaks will be less damaged. However, with a radiational freeze, windbreaks will limit mixing of warmer air aloft and could result in greater freeze damage. Therefore, windbreak design should not only provide for equipment access, but also for air drainage.
Q. I have chemicals applied by aircraft. Will windbreaks be a problem?
A. Applicators using fixed wing aircraft require a minimum of 1200 horizontal feet to make a safe pass over a grove. Rotary wing applicators can operate in a shorter lateral distance, but may need at least 25 to 30 feet clearance between the edge of the windbreak and the adjacent rows of citrus trees to operate efficiently and safely. Windbreaks planted parallel to the rows with no cross windbreaks can still be effective and allow aerial application. Windbreak height is not viewed as problematic by either type of applicator.
Q. How can I learn about wind speeds and patterns in my area?
A. The University of Florida , IFAS, Cooperative Extension operates the Florida Automated Weather Network ( http://fawn.ifas.ufl.edu/ ). Data gathering sites are located throughout the State. The data available from your local FAWN site can be used to conveniently prepare summaries of the wind patterns in your area.
Q. If I plan sufficiently in advance, can a cost-share be obtained through the NRCS Environmental Quality Incentive Program (EQIP)?
A. Windbreaks essentially for canker management have been added in Florida to the Federal EQIP. Contact your District Conservationist for details and application information. To score well on your application review, remember that certain minimum specifications apply and points are earned for meeting the NRCS overall objectives. Any proposed cost-share that enhances and protects the environment will have rating advantages.