Groundcovers for Coastal Landscapes
Groundcovers for Coastal Areas
This is part of a multi-part series on groundcover plants for Florida. Other parts of this series include:
Areas along the coast are hostile environments for most plants. Between the driving winds, salt-laden air, and saline soil, many plants just cannot cope with all the challenges. Fortunately, there are hardy plants that have adapted to life along the sea shore. The following list of plants can thrive in coastal conditions and help stabilize fragile beach dunes and coastal soils. If you are a landscape architect candidate preparing to take the Florida LARE Section F, you will want to know about plants that stabilize the dunes.
Now, let’s look at the plants that thrive along the coast while preserving the soil and sand.
Coastal Groundcovers
Cakile lanceolata (sea rocket)
Searocket is best used to hold loose sand in place such as the beach dune system. It grows to two feet tall and wide and has white flowers. It is reputed to be hurricane and wind resistant and is commonly found on both the Atlantic and Gulf of Mexico sides of the state. This native species blooms from late winter into autumn.
Canavalia maritima (beach bean, bay bean)
Bay Bean is a very fast-growing, herbaceous trailing vine which can be found all over the coastal regions around the Gulf of Mexico and peninsula of Florida. Stems reach a length of more than 20 feet and 1 inch think. Each compound leaf is made up of three leaflets 2–3 inches in diameter, which will fold themselves when exposed to hot sunlight. The flowers are purplish pink and 2 inches long. Bay bean can be found snaking its way to the ocean from shrubby shorelines and coastal shrub. It sets down roots at nodes as it trails across beaches and dunes, the roots forming networks that aid in stabilizing sands. The plant prefers warmth and can tolerate periods of drought, but prefers full sun. The sturdy, fast growing beach bean thrives in almost any well drained soil. It is highly salt tolerant. It will have to be pruned to be kept in check. Beach bean is drought tolerant. It tolerates watering as long as the soil has excellent drainage. Canavalia maritima is hardy in USDA Zones 9-11. This species is also known as Canavalia rosea. Find out more about this species here.
Cenchrus tribuloides (sandspur)
Sandspur is a grass of the eastern United States and tropical America having spikelets enclosed in prickly burs. This hardy grass protects beach habitat from vehicular traffic, trash dumping, and other degrading human activities and is used for shoreline protection. It is usually found on dunes, sandy fields and woods in the outer coastal plain.
Croton punctatus (beach croton)
Croton punctuates is part of beach emergent vegetation and grows up to 6 feet tall (but usually grows smaller). It is a small woody shrub that has grayish-green, fuzzy, round or oval leaves. The leaf terminal end is either broadly or narrowly rounded or somewhat pointed and the leaf margins are slightly reddish in color. The inconspicuous flowers occur in small clusters and are light green. Use as a shrubby groundcover to hold sand and direct pedestrian circulation on beach berms.
Gaillardia pulchella (firewheel)
This sturdy North American native forms attractive, 12- to 24-inch-tall, rounded clumps of soft, hairy, divided leaves and single, semidouble, or double flowers held on long stems above the foliage. Appearing throughout the summer, the two- to three-inch-wide flowers are available in yellow, orange, red, or bicolors, and make excellent, long-lasting cut flowers. The brilliant blossoms are quite attractive to butterflies, and these annual flowers will normally reseed themselves quite readily.
Suitable for growing along the beaches right on the dunes, gaillardia does best in light, very well-drained soils in full sun locations, enduring heat, sandy soil, and drought extremely well.
Gaillardia shows well in a mass planting spaced two to three feet apart, as an edging plant along a walk or driveway, or as an accent in a perennial garden or in front of a shrubbery border. Do not over-water since this could induce root rot.
Cultivars include ‘Yellow Sun’, bright yellow blooms, and ‘Red Plume’, vibrant, dark red blossoms. Read more about Gaillardia here.
Helianthus debilis (dune sunflower)
The beach sunflower is a spreading perennial that has attractive, small, sunflower-like flower heads, which are borne throughout the year. These showy flowers have 10 to 20 pale yellow rays that encircle a purplish-brown disk that is ½ to 1 inch wide. Different species of butterflies are attracted to these charming flowers. The 3-inch-wide flowers of this plant are followed by small seeds that readily germinate to produce plantlets. The beach sunflower has small, dark green, deltoid leaves that are irregularly lobed and toothed. These glossy leaves are roughly pubescent and attain a length of 4 inches.
Beach sunflower is often used as a flowering ground cover along and near the beach and reaches a height of about 18 inches. This plant spreads by underground runners and will quickly fill in an area if provided with occasional irrigation along the beach front. Over irrigation in other locations can slow growth and cause plant decline. One or two applications of fertilizer during the year will encourage plants to establish and cover the ground quickly. It looks great when massed as a ground cover. The cut flowers are charming in arrangements indoors.
The beach sunflower grows best on well-drained sandy soils. This plant will not tolerate over-watering or over fertilizing and is very drought tolerant. It needs to be placed in an area that receives full sun and will endure high levels of salt spray. Beach sunflower is an annual in those areas that have freezing temperatures in the winter; however, it will reseed itself or act as a perennial in central Florida. Read more about dune sunflower here.
Hydrocotyle bonariensis (beach pennywort)
Beach pennywort lives in sandy areas along the coast in very dry lands that are occasionally flooded. Colonizes sandy ground and disturbed foreshore sites, estuaries, coastline, sand dunes and ponds. Hydrocotyle bonariensis has also displayed a tendency to prefer and be stronger at higher elevations. Numerous white to creamy yellow flowers occur on flower stalks can be 12 inches tall. Stems creep and root at the nodes and spreads by rhizomes.
Ipomoea imperati (beach morning glory)
Beach morning glory is a perennial herbaceous vine that has creeping stems that root at the nodes. Flowers are white and highly attractive. It grows on sandy dunes where it holds sand and stabilized sandy areas. It tolerates full sun and coastal conditions including salt-laden air and occasional inundation. It will grow in irrigated areas if the soil is well-drained. Like many coastal species, this one occurs along the Florida coast as well as other parts of the tropics and subtropics.
Ipomoea pes-caprae (railroad vine, beach morning glory)
The beach morning glory is an herbaceous vine that grows wild on ocean shores from Florida to Texas and Georgia. This plant reaches a height of 4 to 6 inches, but the stems may creep along the ground to a length of 75 feet. It roots and occasionally branches from the nodes and develops a long, thick, starchy root. The 2 1/2- to 4-inch-long leaves are thick, smooth, and two-lobed; the leaf shape reminds one of a goat’s footprint or perhaps an orchid tree leaf. The beach morning glory is truly charming when in bloom. Funnel-shaped flowers that are 2 ½ to 3 inches wide occur in the summer and fall. The flowers are pinkish lavender with purple-red throats. They open in the early morning and close before noon each day that the plant is in bloom. Small, round seedpods that contain four velvety, dark brown seeds appear on this plant after flowering.
The beach morning glory is well adapted to beaches and coastal dunes. It is useful as a sand binder and ground cover, even on the ocean side of the first dune. They grow right down to the high tide mark on the beach. Plant on 3-foot centers to quickly form a ground cover. It may not be well suited for home landscapes because it grows too quickly and has a very open growth habit.
This full sun plant will prosper on most well-drained soils. It grows very rapidly and needs to be pruned and contained if planted in a landscape. To say the plant grows quickly is to preach the truth. The beach morning glory will tolerate very high levels of salt spray but cannot endure over watering. Basically, plant it, water a few times and leave the sprinkler off. Read more about railroad vine here.
Ipomosis rubra (standing cypress)
Standing cypress is stunningly beautiful and easy to cultivate in garden settings. Showy, red, tubular flowers, widely flaring at the rim, are marked with orange or yellowish spots inside. Flowers are arranged in a thick spike, opening from the tip of the stem downward. When the bloom stalk is through blooming, you can prune it off to allow replacement stalk to grow and flower. Staying cypress grows well in dry, sandy or rocky fields and open woods. It prefers well-drained sand, loam, or limestone soils and does well on back dunes. This species has a biennial growth habit and the first year of growth will produce a ferny rosette followed by a flower spike the second year. When the spike has bloomed out, cut it off, and new spikes will be formed.
Iva imbricata (beach elder)
Seacoast marshelder (Iva imbricata), occurs on coastal dunes throughout the south Atlantic and Gulf region (coastal Virginia to coastal Texas) and is used for dune restoration and stabilization projects. The plant has sparse, woody, upright stems reaching heights of 1 to 4 feet. Leaves are fleshy, narrow and lance-shaped and arrangement may be alternate or opposite. Flowers are not very showy, occur on terminal racemes with a bract below each flower, and have small lavender petals. The flowers appear in late summer and continue into early fall. The plant is prized for its ability to accumulate sand, thereby producing low, rounded dunes. Read more about this useful dune-protecting species here.
Panicum amarum (dune panic grass)
Panicum amarum is a species of grass known by the common name bitter panicgrass. It is native to North America, where it is found in coastal regions along the East Coast and Gulf Coast of the United States and into northeastern Mexico. It also occurs in the Bahamas and in Cuba. This smooth grass can grow as tall as 4 feet and spreads slowly through its rhizome growth forming clumps. The flowers are airy, emerging in the fall, and persisting as a light beige color throughout the winter. This is a low-maintenance landscape plant; however, because of its size and rhizomous growth habit, adequate space is essential. Bitter panicgrass is commonly found on high dunes and plays an important role in dune stabilization.
Uniola paniculata (sea oats)
Sea oats once blanketed the coastal landscape along the southeastern United States from North Carolina to south Florida. Now they are endangered. They were the primary dune stabilizer and will grow right up to the high tide mark along the beach. Plants spread by means of underground rhizomes. Each plant develops a showy inflorescence about 5 feet tall. The oat-like fruit persists on the plant, giving the plant a nice texture as the wind blows. Existing plants should be saved wherever possible, and planting should be encouraged along the beaches.
You could not find a more drought tolerant plant for along the coast. Plant sea oats several feet apart to stabilize dunes along the beach. It is illegal to collect plants from the wild without special permits. Place sea oats in an area of the landscape that receives full sun. This plant may be grown throughout Florida.
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