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SALT of the EARTH

Your patio faces the Gulf of Mexico. Maybe your yard backs up to Tampa Bay, the Intracoastal Waterway, or one of the dozens of neighborhood canals in this area.

Most of your plants have to be in containers _ and all of them are whipped daily by a stiff, salty breeze.

How do you keep a healthy garden under those conditions?

It's a challenge. The plants you choose have to fill several requirements: salt tolerance; wind tolerance; heat tolerance; container tolerance. We're talking about tough plants here _ the Marines of the plant kingdom.

The hardiest plants are those that are indigenous to a particular locale. Some of these, especially small trees and shrubs, are attractive and can be used to good effect in a seaside garden or as container specimens. The collection can then be broadened with careful selection of salt-tolerant non-native species.

The most critical factor in waterfront gardening is the problem of wind-borne salt spray. As the wind carries the spray inland, it leaves salt deposits on plants, which causes water to leach out in a process called exosmosis. In plants not naturally adapted to those conditions, salt spray can cause burning and loss of leaves.

Salt, wind and heat

Salt tolerance is relative. Plants are usually ranked as salt tolerant, moderately salt tolerant, or having slight or low tolerance.

Salt-tolerant plants are highly resistant to salt drift and can be used in exposed coastal sites. Plants that occur naturally near salt water sometimes have special adaptations that help them deal with salt spray.

Railroad vine (Ipomoea pes-caprae) has glands on the surface of its leaves that excrete excess salt and enable the plant to grow in extremely salty soils. This tough plant is valuable as a sand binder and ground cover for beachfront locations. It also can be trained to climb on a fence or trellis to provide a salt barrier for more sensitive plants.

Moderately salt-tolerant plants can survive with some salt spray but grow best when protected by buildings, fences or plantings of more salt-tolerant species.

Plants with low tolerance should be used well back from the waterfront, where they will be protected by buildings, fences or other plants. For example, you might plant them on the leeward side of a house, away from sea breezes, letting the building block them. Even then, those plants should be sprayed with fresh water several times a week to remove salt from their leaves.

Plants that face the water also must be able to withstand a great deal of wind. The nearly constant on-shore breezes can dehydrate plants and even damage their foliage. You can overcome the problem by sheltering plants from prevailing winds or by choosing drought-resistant species that will stand up to the loss of water.

There also is a considerable amount of heat and light reflected from the surface of the water and from large expanses of sandy beaches. You should make sure your waterfront garden receives a bit of shade every day.

Fortunately for us, neither winds nor salt spray are as bad from the Gulf as they are on the Atlantic coast. Many moderately salt-tolerant plants will thrive here.

Container growing presents other challenges. The roots of a plant in a pot are restricted and the soil dries out more quickly than if the plant is in the ground. This is especially true of porous containers such as terra cotta. On a gulffront patio where wind and heat are constant factors, the gardener must be vigilant in watering container-grown plants.

Trees

Trees form the backbone of any garden. Even if you're growing things on a 10th-floor balcony, you can have them.

Small, slow-growing trees can be kept happy for a number of years in a large container. Choose sturdy pots that won't tip over when breezes whip up. Wooden half-barrels and terra cotta tubs, pots and troughs will give larger plants the weight needed for stability. A container with a wide, tub shape is more stable than a tall pot which will tip easily in the wind.

Varying the shapes and sizes of containers you use, as well as the texture and color of the plants you put in them will create visual interest. Choose trees for the qualities you most want _ shade, fruit, flowers or architectural qualities of the foliage.

Madagascar olive (Noronhia emarginata) is a slow-growing evergreen tree that can reach 20 feet. It has high salt- and wind-resistance and edible fruit. Loquat (Eriobotrya japonica) is a hardy, medium salt-tolerant evergreen tree with small yellow-orange fruits that ripen several times a year. They are used for jellies or eaten fresh.

Larger shrubs can be pruned to one or several trunks and used as small trees in a patio setting. Oleander (Nerium oleander) is an evergreen shrub with flowers in reds, pinks, yellows or white. It blooms throughout the warm season and makes an excellent waterfront shrub. It likes full sun and is drought-resistant. Compact cultivars are available, which are suitable for smaller containers. (Note: All parts of the oleander are highly toxic. Keep this in mind if pets or children share the patio or area where your oleander will be.)

Southern wax myrtle (Myrica cerifera) is a native shrub that grows to 20 feet and can be used as a barrier or trimmed to a multitrunk tree. The leaves are fragrant when crushed and provide good cover for small birds. The leaves can be used to flavor meats or stews, with the same effect as bay leaves. The fruit of the wax myrtle is covered with a blue-gray wax which is used to make bayberry candles.

Palms will bring the ambience of the tropics to your waterfront garden. A few are both container- and salt-hardy. The European fan palm (Chamaerops humilis) will grow to 10 feet. The leaves are broad, palmately shaped with deeply divided segments. The color of the leaves is green, blue-green or silvery green. This palm's growth is extremely slow, allowing it to be grown in a large container for many years. The frond petioles have sharp teeth, so keep it in a corner, away from human traffic.

Lady palm (Rhapis excelsa) is an attractive clustering palm that grows to 7 feet and has moderate salt tolerance. This is a slow-growing tree that can be maintained in a container for some time. It grows best in partial shade where the leaves will stay deep, shiny green. A healthy lady palm is a striking ornament, lending a touch of class to any setting. There's disagreement on its cold hardiness, so to be safe, bring it inside if a freeze is predicted.

The cardboard palm (Zamia furfuracea) looks like a trunkless palm, but is actually a cycad. This plant is finding wide use in landscaping, commonly used as groundcover or in a planter. It is native to eastern Mexico, where it grows in coastal areas exposed to salt spray.

The understory

Underplantings for trees in containers can include salt-tolerant shrubs such as the lavender lantana (Lantana montevidensis) that nicely cascades, or one of the trailing plants usually seen as ground cover _ purple heart (Setcreasea pallida) or wandering Jew (Zebrina pendula), both considered moderately salt-tolerant. Any of these also could be used in hanging baskets to good effect.

Shrubs can add a brilliant spot of color. Bougainvillea and ixora (Ixora coccinea) come in a number of colors. Bougainvillea is considered highly salt-tolerant; ixora has moderate tolerance.

Incidental plants for texture and shape include the agaves. Spineless yucca (Yucca elephantipes) is moderately salt-tolerant and safer to plant around people than the type armed with stiff spine tips. Aloe (Aloe barbadensis) is a good companion plant with agaves and is salt-tolerant. There are a number of interesting varieties of this succulent perennial, including dwarfs.

For a whimsical touch, plant creeping fig (Ficus pumila) on a wire topiary, train it over a tomato cage, trellis or bamboo tripod.

Annuals can be used wherever color is needed. For container-grown annuals, use liquid fertilizer of the "bloom-booster" type.

All container plants do best with liquid and slow-release fertilizers. Follow label directions.

PASS-A-GRILLE PATIO

Marjorie Friedman's gardening philosophy might best be called laissez faire. "I don't believe in forcing anything," she says. "If it's happy it'll grow." Just a few feet from her apartment patio, sea oats fringe the edge of St. Petersburg Beach. There's salt in the air and sand underfoot. And still Friedman's patchwork quilt of a garden thrives. She plants whatever neighbors give her; she also walks around the neighborhood and salvages cuttings from brush piles left by lawn services. A bougainvillea covers a trellis next to her small porch and jasmines fill the air with sweet scent. Window boxes, anchored with fishing line so they won't blow away, house an allamanda and other vining tropicals. In the tiny strip of sand along the sidewalk, cacti and draceana share space with periwinkles, gardenias and throw-away Christmas poinsettias. There's even a diminutive banana tree. Friedman added a little topsoil and 10-10-10 to the sand, and every once in a while she sprays Miracle Gro on her plants. Other than that, the Gulf-front garden is self-maintaining. Perfect for a gardener who likes to let things be.

ON THE DOCK OF THE BAY

Despite salt air and frequent wind that hurts plants, Mary Newby has achieved colorful success this year with raised beds at her home along Boca Ciega Bay on Treasure Island. A graduate of the Pinellas extension's Master Gardener program, she credits the unusual amount of rain this summer for her many flowers. But the loads of topsoil and manure she dug in certainly helped the perennials: a huge bed of yellow lantana that grew from just one plant; pentas in white, red, magenta and pink; blue porterweed; white and orange Linearis and other zinnias; pink, red and blue sage; lavender blue Duranta and Manoa's beauty. In the 21 years Newby has lived here with her husband, Irv, their waterfront property has been flooded two or three times but always recovered.

Other species for waterfront gardens

Trees

Chaste-tree (Vitex spp.) To 12 feet. Cold-hardy. Purple flowers. Most common variety has variegated green and cream leaves. Trunk often takes on interesting shapes. Bark rough and attractive. Moderate salt tolerance.

Tabebuia (Tabebuia argentea). Bright yellow springtime flowers. Picturesque gray branches. Salt tolerant. Protected locations.

Erect bottlebrush (Callistemon rigidus). To 15 feet. Small flowering tree with moderate salt tolerance. Scarlet flowers borne in cylindrical spikes to three inches long.

Weeping bottlebrush (Callistemon viminalis). Also to 15 feet with red flowers, but growth habit is low-branching and pendulous.

Florida privet, also called wild olive (Forestiera segregata). To 10 feet. Native hedge plant with good salt and drought tolerance. Ripe fruits look like miniature olives and are attractive to wildlife. Tiny flowers are attractive to butterflies and other nectar-feeding insects. An underused native shrub that has many values for the landscape and is especially useful for seaside locations.

Pittosporum (Pittosporum tobira). To 15 feet but usually seen much smaller. Interesting shape makes it appealing for containers. Also comes with variegated foliage. High salt tolerance.

Palms

Saw palmetto (Serenoa repens). Hardy native. Blue-green fan-shaped fronds. Also look for Sabal minor, a dwarf palmetto.

Seashore palm (Allagoptera arenaria). Slow growth rate. Protect from frost. Trunkless clustering palm. Leaves green above, silvery below, with eye-catching appeal as they flutter in the sea breeze.

Christmas palm or Manila palm (Veitchia merrillii). Typical height around 15 feet. Neat, solitary palm. Glossy red fruit ripens around Christmas. Moderate salt tolerance. Protect from frost.

Shrubs

Natal plum (Carissa grandiflora). Highly recommended for seaside use. Use in borders, screens or foundation plantings. Compact cultivars can be used for ground cover. Excellent hedge plant or specimen because of its salt tolerance. Edible red fruit.

Lantana (Lantana camara). Many colors available. Note: poisonous berries.

Plumbago (Plumbago auriculata). Popular shrub for its profuse blue flowers. Sprawling habit makes it a good specimen for urns.

Thryallis (Galphimia gracilis). Evergreen shrub. Brittle branches best kept trimmed for appearance and wind resistance. Constantly covered with small yellow flowers. Moderate salt tolerance.

Herbaceous plants

Crinum lily (Crinum asiaticum). Thick, leathery leaves with white flowers standing above the arching leaves. A fine underplanting for trees and palms. Blends well with yuccas. Needs sunny exposure.

Spiral flag (Costus igneus). To one foot. Dies back during freezes, but comes back from roots in spring. Perennial shrub, spreading by rhizomes to form dense mounds. Orange-red flowers in summer. Moderate salt tolerance. Full sun or partial shade. Fertile, moist soil. Good pot specimen.

Pine cone lily, also called wild ginger (Zingiber zerumbet). To 6 feet with variable spread. Moderate salt tolerance. Tuberous, growing from aromatic rhizomes. Dies back to ground in winter, but comes back from roots in spring. Grown in Central and South Florida as a specimen for its unusual inflorescence, shaped like a pine cone and borne on a stalk separate from the leaves.

Flowers

Perennials: Coreopsis; dusty miller; butterfly weed (Asclepias tuberosa); chrysanthemum; liriope (Liriope spicata); goldenrod; snow-on-the-mountain (Euphorbia marginata); sweet alyssum.

Annuals: Blanket flower (Gaillardia pulchella); cleome; cosmos; pinks (Dianthus); sand verbena; nasturtium; Mexican sunflower (Tithonia); nicotiana; zinnia; portulaca; phlox; gazania; beach sunflower (Helianthus debilis).

Vines

Cape honeysuckle (Tecomaria capensis); Mexican flame vine (Senecio confusus); Virginia creeper (Parthenocissus quinquefolia); rubber vine (Crypotostegia grandiflora); pink allamanda (Mandevilla splendens).

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