Shelter from the continuous winds and abnormally high tides is necessary for the seaside landscape and garden. Plants standing out in the open wind all the time transpire rapidly and lose great amounts of water regardless of how good the soil is, and salt spray is just an added insult. Reducing water loss in the garden by giving shelter from the prevailing winds and salt spray is also essential in order to grow a large variety of otherwise unadaptable plants. This type of shelter is given by erecting temporary board fences or burlap attached to poles or taller wooden structures. Permanent year-round protection can be provided by planting windbreaks and screens of especially rugged and resistant trees and shrubs as well as by taking advantage of every possible dune or rise of ground that would aid in this respect.
The purpose of a windbreak is to reduce the force of the wind and associated salt spray in the sheltered zone as well as to provide erosion control. Windbreaks vary in effectiveness in this regard, depending upon their height, porosity and length. The higher the windbreak, the greater the distance of its downwind as well as its upwind influence.
For the best wind reduction and greatest downwind influence, the windbreak should be most porous near the ground, where the wind speed is lowest. Ideally, the density of the barrier should increase with the height in proportion to the logarithmic nature of the wind speed profile. By increasing the porosity of a windbreak to about 50 percent, the penetrating wind prevents the turbulent return of air that has overtopped the barriers to the ground close by.
The longer the windbreak, the more constant is its influence. If a barrier is too short or if it has large gaps in it, jetting effects may actually increase, rather than reduce, the wind speed and the consequent damage to plants near the gaps.
For a long time the most popular tree being used as a windbreak was the Japanese black pine, which is seen growing to about 15 feet tall and about 10 to 15 feet wide if properly pruned. Unfortunately, large-scale plantings of these evergreens have created homogeneous communities that are susceptible to several diseases and insects. In addition, plantings that are made too deep have resulted in spindly transplants that die after two or three years.
Another popular and naturally occurring tree used as a windbreak is the eastern red cedar. This tree can grow to 30 feet but is more common at 8 to 12 feet. It’s cylindrical in shape, becoming conical near the apex. When closely planted, and with the tops sheared, this tree forms a dense break that resists insects, disease and drought.
Privet is now the most common shrub-hedge material used as both a screen and windbreak. The fact that it is deciduous seems to be of little consequence, as it tends to leaf out before the summer visitors arrive and does not drop its foliage until late fall or early winter.
Many years ago there were actually shortages of this plant, but over the years local nurseries have planted and shaped miles and miles of privet stock, so you can usually purchase ready-to-install hedge material at various heights. But privet has also succumbed to an insect problem and has to be used with that caution.
If it is necessary to start with pure sand and beachfront, the first thing is to build up a dune and get a vegetation cover on the sand to prevent its blowing and shifting. This is accomplished by placing two rows of snow fence about 40 feet apart, parallel or slightly askew to the shoreline at right angles to the prevailing wind. This stops the sand from blowing, and a dune is built up on the same principle that makes the fencing so effective in stopping or retarding blowing snow. Check with your local town of village, though, to find out what regulations may apply to your installing such a dune builder and when it can be done.
When the dune is sufficiently high, it is planted with American beach grass, which spreads vigorously through underground stems. Some caution has to be advised at this point, though, because certain local, state and federal laws limit when and how the grading and planting can be done.
One Southampton homeowner placed an order with a Delaware firm one fall for 50,000 Ammophila (beach grass) plants, which he was planning to use in stabilizing his oceanfront property. The New York State Department of Environmental Conservation was properly notified and it granted verbal permission to go ahead on the project, but stipulated that it was to be notified before any grading or planting was done.
When the plants arrived, the DEC was notified, but put an immediate hold on the project until severe beach erosion that had occurred in late March was replaced by nature, a task that was to take 45 days and virtually ruined the planting plans for that year.
The American beach grass is about the best stabilizer available when separated and planted in small clumps on 18-inch centers. The roots are generally set 8 inches deep between October and April. Temporary irrigation may be set up, but again there are laws and regulations that may control not only the planting but the irrigation as well.
Other ground covers that have been experimented with and have shown varying degrees of success are broom sedge (Andropogon virginicus); seacoast bluestem (A. littoralis); sea oats (Uniola paniculata); veld grass (Ehrharta amarum); Volga wild rye (Elymus giganta) and weeping lovegrass (Eragrostis curvula).
The next step is erecting windbreaks and adding organic matter so that plants other than the beach grass can be grown. When this is done properly, the result will enable the gardener to plant many other varied genera often within 200 feet of the high water line. When working in dunes, though, remember that they are extremely fragile and may even contain protected plant species. The next problem to consider is salt-water flooding. Such floods can but rarely do permanent injury, as they are usually preceded and followed by rain showers. Even in the case of extensive flooding caused by hurricanes, plantings generally show some foliar damage, but it is nearly always temporary.
Salt spray, on the other hand, is a more persistent problem that can cause lasting damage or complete failure. Obviously, any plant that is continuously subjected to salt spray is at a disadvantage if it hasn’t learned to adapt and survive. I’m always amazed at sea lavender, which grows in the tidal zone of many local bays. It can be submerged in salt water often for half of its life and yet every year it sends it blooms skyward.
If a large amount of salt-water spray is deposited on tender foliage that has not properly matured, damage will be greater than if the foliage were mature. The first thing to do after high wind storms that come off the ocean is to spray the plants thoroughly and forcibly with plenty of fresh water to wash off as much salt as possible.
While it is a bit out of date, see if you can track down a copy of “The Salty Thumb,” published in 1967 by the Montauk Village Association. There is also “Gardening by the Sea” by James Foley, and there are several other seaside gardening books. So, like the doctor said, watch the salt and keep growing.