Trees of South Florida–Part 4
Trees of South Florida – Part 4
In part 4 of this series on native and adapted trees for use in South Florida landscapes, we will discuss oaks and other species that can be used in planting designs. If you are a landscape architect candidate preparing to take Florida Section F of the landscape architect registration exam, you need to be familiar with the plant life of South Florida. I was surprised by how much of the test seemed to revolve around the southernmost counties in the state.
Since there are so many great trees adapted to grow in the mild South Florida climate, this list is broken up into several articles.
- Trees for South Florida–Part 1 (A-C)
- Trees for South Florida–Part 2 (D-I)
- Trees for South Florida–Part 3 (J-P)
- Trees for South Florida–Part 4 (Q-Z)
Landscape architect candidates should be knowledgeable about the following species for southern Florida landscapes.
Trees for South Florida
Quercus geminata (sand live oak)
This species is commonly known as sand live oak because it exhibits many morphological characteristics similar to those of the live oak (Quercus virginiana). However, it grows in sandy, scrub habitat and does not reach the towering dimensions of the live oak.
This small, native, evergreen tree is found along the coastal plain throughout most of peninsular Florida. It can be found in the xeric sandy soils of coastal dunes, hardwood forests, mixed pine uplands, scrub, and sandhills. Sand live oak grows best in partial shade to full sun and reaches heights of 50 feet. The thick, leathery leaves are simple and alternate and range from 1½ to 2½ inches long. They are elliptical in shape with coarse veins that are deeply pressed into the leaf surface, and they have smooth margins that are, in many cases, highly revolute or inwardly curling. The upper surface of the leaf is dark green and the underside is a dull gray to almost whitish color with sparse to copious pubescence or hairs. The presence of this leaf pubescence, along with the upper surface venation, can aid in distinguishing sand live oak from live oak. The twigs also will have some pubescence when they are immature. The bark is rough to the touch, dark brown, and deeply furrowed. Acorns range from 5/8 to 1 inch long with 1/3 of the dark brown, egg-shaped nut enclosed in a scaly, whitish gray cup. Acorns are produced annually and appear in groups of 1 to 3 in the fall.
Though it is a smaller-statured tree, sand live oak may be used for landscaping in the same way that live oak is used. A fact to keep in mind when selecting sand live oak at a nursery is that some forms are shrubbier and less treelike than others. Before making a purchase, ask the nursery staff whether mature specimens are available to view the growth form. This will ensure that trees purchased will meet any sought-after requirements. Homeowners and others should be aware that the leaves and acorns of this tree are high in tannin, which can stain concrete. Read more about this species here.
Quercus virginiana (live oak)
A large, sprawling, picturesque tree, usually graced with Spanish moss and strongly reminiscent of the Old South. Live oak is one of the broadest spreading of the oaks, providing large areas of deep, inviting shade. It is the state tree of Georgia. Reaching 40 to 60 feet in height with a 60 to 100 foot spread and usually possessing many sinuously curved trunks and branches, live oak is an impressive sight for any large-scale landscape. An amazingly durable American native, it can measure its lifetime in centuries if properly located and cared for in the landscape. It makes an excellent street tree in the South. Unfortunately, oak wilt has devastated the tree in parts of central Texas. Give it plenty of room since the trunk can grow to more than six feet in diameter.
Once established, live oak will thrive in almost any location and has very good wind resistance. Live oak is a tough, enduring tree that will respond with vigorous growth to plentiful moisture on well-drained soil. Like other oaks, care must be taken to develop a strong branch structure early in the life of the tree. Be sure to eliminate multiple trunks and branches which form a narrow angle with the trunk as these are likely to split from the tree as it grows older.
Be sure that adequate soil space is given to live oak. Although roots will grow under curbs and sidewalks when planted in confined soil spaces allowing the tree to thrive in urban sites, in time, they lift sidewalks, curbs, and driveways. This may be a small price to pay for the bountiful shade cast by a row of healthy trees.
One of the biggest problems with live oak in our cities is the lack of pruning. Therefore, it is not a plant-and-forget tree. Because this tree can live for such a long time, it is very important to develop proper trunk and branch structure early in the life of the tree. Following planting in the nursery, prune the tree each year for the first three years, then every five years to age 30. This program will help ensure that the tree develops into a strong, long-lived fixture in the community, and will help develop the 14 to 15 foot tall vehicle clearance needed for planting along city streets.
Best growth is made in moist, acid soil, sand, loam, or clay, but the tree is amazingly adapted to drought. It also tolerates alkaline soil well. Young trees grow three feet each year and the trunk adds about one-inch in diameter under nursery conditions. Construction-impacted trees take a long time to die, giving live oak a reputation for being a tough tree. It is usually the last tree to die around a newly constructed building. Find out more about live oak here.
Rhizophora mangle (red mangrove)
Red mangrove is one of the most valuable trees for creating and preserving shorelines in south Florida and the Caribbean Basin. Sediments depositing among their adventitious prop roots can eventually build up to create land. Seeds often germinate while they are still on the tree. After they drop, they float to a new location where they can begin growing in the sediment below the water surface. Red mangroves will often be seen growing in shallow lagoons away from the land. Plants typically reach 20 feet tall, although old specimens 35 feet tall are not uncommon in undisturbed, natural settings. Plants respond poorly to pruning. Read more here.
Sambucus mexicana (elderberry)
Mexican elder is a semi-evergreen small tree, reaching up to 30 feet in height. Most open-grown specimens do not reach this height as they grow wider than tall. The light green, thick, leathery, pinnately compound leaves are often browsed by deer and livestock. The four to eight-inch-wide, flat cymes of yellow/white blooms appear mainly from April to June but in its native habitat may also occur at various times throughout the year after heavy rains. The small, blue/black fruits which follow the blooms are quite popular with birds and can be used to make wine or pies, and were reportedly even dried by Indians to be used at a later time. Fruits appear white because they are covered with a thick, waxy coating. A dye can be made from the stems and has been used to color baskets.
Trees are best located in the open where they can develop their low, wide-spreading, uniform crown. It might be planted near a patio, or as a small shade tree in a backyard garden but the dropping fruit can be messy on brick, concrete and other hard surfaces. Young trees often require training and pruning to speed formation of a uniform crown. Save the more upright branches and remove the drooping ones to create greater clearance beneath the canopy. Mexican elder should be grown in full sun on well-drained soil. Find out more about this species here.
Senna polyphylla (desert cassia)
Desert Cassia (Senna) is a petite tree with a beautiful cascading habit. The graceful branches are covered year-round with tiny leaves, and 1″ vivid yellow flowers are produced fall to spring. These blooms attract butterflies. This garden gem may be petite and graceful but it also excels in the toughest conditions and is useful in xeriscapes. It was even chosen “Plant of the year” in 1999 by the Florida Nurserymen & Growers Associations. The tree grows in USDA plant hardiness zones 10-11 which restricts its range to south Florida. This species grows to 10-15 feet tall and has an equal spread. It exhibits medium salt and drought tolerance.
Simarouba glauca (paradise tree)
The pinnately compound, 16-inch leaves of paradise-tree have multiple, three-inch-long, shiny, leathery, oblong leaflets which are reddish when young. An upright tree when young, paradise-tree ultimately reaches 50 feet in height with a 30-foot spread and creates a dense, rounded crown at maturity. The tiny, inconspicuous, yellowish, springtime blooms on this frost-sensitive tree are followed by small clusters of dark purple, one-inch-long, edible fruits. Although paradise-tree produces desirable shade, the seeds and fruits are messy and will stain hard surfaces, and the shallow surface roots are troublesome to sidewalks and driveways and make it difficult to operate a lawn mower beneath the canopy. The coarse leaf texture and light green, compound foliage allows this tree to “stand out” in a crowd. It could be used as a boulevard or median street tree. Plant them on 25 to 30 foot centers to form a solid canopy above. Paradise-tree grows in full sun or partial shade on almost any well-drained soil. A native to south Florida, it will grow quickly on rich soils high in organic matter and should be protected from frost. Read more about this tree here.
Swietenia mahagoni (West Indian mahogany)
This large, semievergreen tree forms a loose, rounded canopy and casts light, dappled shade, suitable for maintaining a lawn beneath. It is one of south Florida’s popular landscape and street trees. Mahogany can reach 75 feet in height with a 50-foot-spread but is more often seen at 40 to 50 feet tall and wide. The dense, strong wood of Mahogany is quite resistant to wind-damage on properly trained trees, making this tree all the more ideal for use as a shade tree or street tree. Trees planted along streets or in medians will form a beautiful canopy overhead. The five-inch-long, brown, woody fruit capsules hang from slender, fuzzy stalks in winter and split while still on the tree when ripe to release winged seeds.
A native of south Florida, mahogany will grow in full sun or partial shade on a wide range of soil types, and is quite resistant to salt spray. Plants will respond with rapid growth to rich, well-drained soil and regular fertilizing. Roots can raise sidewalks and curbs when planted only five or six feet away. Root deflectors and barriers which direct roots to a deeper soil layer are recommended for this and other large-growing trees with surface root problems. Be sure that trees are planted and maintained with a central leader to develop a strong trunk and branch structure. Trees often develop several upright multiple leaders which significantly reduces the wind and storm tolerance of any tree, including mahogany. Prune and train the tree while it is young to develop several major limbs spaced several feet apart along a central trunk. Do not allow branches to grow larger than about two-thirds the diameter of the trunk. This will increase the life span of mahogany. Find out more here.
Tabebuia caraiba (silver trumpet tree)
An ideal patio, specimen, or lawn tree, the Tabebuias are small, 15- to 25-foot tall, evergreen trees with silvery foliage and deeply furrowed, silvery bark on picturesque, contorted branches and trunk. The crown is usually asymmetrical with two or three major trunks or branches dominating the crown. During late winter and sporadically throughout the year, they put on a brilliant display composed of a multitude of two to three-inch-long, golden yellow, trumpet-shaped blooms borne in terminal flower clusters. The leaves often drop just before the flowers appear.
A native of tropical America, trumpet tree can be grown in full sun or partial shade on any reasonably fertile soil with moderate moisture. Trees should be protected from frost. Although some will leaf out following a freeze, the tree is often weakened and grows poorly. The wood becomes brittle with age and can break easily in strong winds but this is not usually a problem since trees are small with an open canopy and should not be cause to eliminate this beautiful tree from your tree palette. To the contrary, it is one of the most beautiful trees in flower which has a place in most landscapes.
The pink trumpet tree (Tabebuia heterophylla) is the one most suited for street tree planting since it is reportedly more sturdy and durable than Tabebuia caraiba. Tabebuia impetigenosa and Tabebuia umbellata are hardy to zone 9b with pink flowers borne on bare branches. Check out this article for more information.
Tabebuia chrysotricha (yellow trumpet tree, golden trumpet tree)
An ideal patio, specimen, or lawn tree, golden trumpet tree is often seen as a small, 15- to 25-foot-tall tree but can reach 50 feet, with a rounded, spreading canopy in a wind-protected area. Sometimes evergreen but most often deciduous, golden trumpet tree has four-inch-long silvery leaves with tan, fuzzy undersides. These leaves drop for a short period in April to May, and it is at this time that the trees put on their heaviest flowering display, the trumpet-shaped, bright yellow blossoms appearing in dense 2.5- to 8-inch-long terminal clusters. Some trees produce a small number of flowers sporadically throughout the warm season. The eight-inch-long seed capsules which follow are brown, hairy, and persist on the tree through the winter.
Golden trumpet tree is very useful as a median street tree for its vivid flower display, asymmetrical habit and drought tolerance. Once established it can survive on rainfall alone and produce an excellent flower display each year. It also makes a nice tree for planting close to the patio or deck where it will cast a light to medium shade below the canopy.
A native of tropical America, golden trumpet tree can be grown best in full sun on any reasonably fertile soil with moderate moisture. Trees should be protected from frost. Although some will leaf out following a freeze, the tree is often weakened and grows poorly. The wood becomes brittle with age and can break easily in strong winds, so it is not often seen larger than about 30 feet tall. But this should not dampen your desire to plant this wonderful tree because it provides such enjoyment in the mean time.
Trees planted with circling roots often fall over as they mature. Be sure to slice the root ball on container-grown trees. Read more here.
Tabebuia heterophylla (pink trumpet tree)
Pink trumpet tree produces a wonderful specimen tree, reaching a height of 50 feet and is covered with terminal panicles of pink to rose-purple, two-inch-wide, showy blossoms in spring. There are few, if any, other flowering trees which can match the beauty of this tree in bloom! Flowers stand out nicely because there are no leaves on the tree during flowering. They contrast nicely against the light grey bark. The palmately compound leaves bear five leaflets, each about two-and-one-half inches long.
Pink trumpet tree would make a nice tree for planting along a boulevard or residential street where there is plenty of soil space for root development. Prune major limbs so they remain about one-half the diameter of the trunk so they remain well secured to the trunk. This is a tree you will want to keep around, once you see it in flower.
Pink trumpet tree should be grown in full sun or partial shade on rich, well-drained soil. Trees flower at an early age. This article has more information.
Tabebuia impetiginosa (purple trumpet tree)
This briefly deciduous tree reaches 15 to 20 feet in height and has a fairly open canopy. Branching is often sparse allowing turf and other sun loving plants to grow beneath the canopy. The dark green, palmately compound, five-inch-long leaves are joined in late winter or early spring by the showy, trumpet-shaped blooms, appearing in dense, rose-pink to purple, terminal panicles. Trees will have a better form if trained to a single trunk and staked until they are six to eight feet tall, at which time they can be allowed to grow naturally.
Use this small tree in an area where any small tree can be used. It might be best to locate it in a shrub border or other out-of-the-way place since the canopy is quite thin, even in full sun. It is probably not as well suited for specimen planting as the other tabebuias.
Purple tabebuia should be grown in full sun on almost any well-drained soil but trees respond especially well to rich soil. Established trees are highly drought-tolerant. Read more here.
Taxodium ascendens (pond cypress)
Similar to baldcypress in that the trunk is perfectly straight 50 to 60 feet tall, pondcypress has a narrower crown, is smaller, and has a more open habit. It is found along the edges of streams and around the edge of swampy ground where water is standing; whereas baldcypress is usually found along stream banks. The bright green, awl-shaped leaves are arranged in an upright row formation along the branches when young, giving a somewhat stiffer and more upright appearance than baldcypress. The leaves turn an attractive light brown in fall before dropping but the bare branches and light brown, ridged bark provide much landscape interest during the winter. The trunk grows unusually thick toward the base, even on young trees. This is thought to provide support for the tree in its wet habitat. The small seeds are used by some birds and squirrels.
Although often seen at water’s edge where it will develop “knees”, or root projections, that will extend above the water for gas exchange, pondcypress can also be grown in dry locations and could make an attractive street tree for a very narrow space. Cypress knees do not generally form on these drier sites. The “knees” do not form as readily as on baldcypress, even on wet sites. It provides a good vertical accent to the landscape and should be used more often in urban areas. The roots do not appear to lift sidewalks and curbs as readily as some other species. Its delicate foliage affords light, dappled shade, and the heartwood is quite strong and resistant to rot. However, most lumber available at lumber yards today is sapwood and is not resistant to rot.
Pondcypress is ideal for wet locations, such as its native habitat of stream banks and mucky soils, but the trees will also grow quite well on almost any soil, including clay, silt, and sand, except alkaline soils with a pH above 7.5. Its drought-avoidance mechanism allows it to drop leaves in extended dry periods but little harm appears to come to the tree. Pondcypress is relatively maintenance-free, requiring pruning only to remove dead wood and unwanted lower branches which persist on the tree. It maintains a desirably straight trunk without pruning and does not form double or multiple leaders as do many large trees. The cultivar ‘Prairie Sentinel’ is narrower than the species. Read more about pond cypress here.
Taxodium distichum (bald cypress)
Narrowly to broadly pyramidal when young, bald cypress eventually develops into a broad-topped, spreading, open specimen when mature. Capable of reaching 100 to 150 feet in height, most landscape specimens are rarely seen in this open form because they are usually much younger and shorter. Trees grow at a moderately fast rate, reaching 40 to 50 feet in about 15 to 25 years. Although it is native to wetlands along running streams, growth is often faster on moist, well-drained soil. The pale green, needle-like leaves turn a brilliant coppery red in fall before dropping, but the bare branches and reddish gray, peeling bark provide much landscape interest during the winter. The trunk grows unusually thick toward the base, even on young trees.
Although often seen at water’s edge where it will develop “knees”, or root projections, that will extend above the water, baldcypress can also be grown in dry locations and makes an attractive lawn, street, or shade tree. Cypress knees do not generally form on these drier sites. Cities from Charlotte, NC, Dallas, TX to Tampa, FL currently use it as a street tree and it should be used more extensively throughout its range in urban landscapes. It provides a good vertical accent to the landscape and should be used more often in urban areas. Baldcypress can be clipped into a formal hedge, creating a wonderful soft screen.
Surprisingly, the roots do not appear to lift sidewalks and curbs as readily as some other species. Its delicate, feathery foliage affords light, dappled shade, and the heartwood of baldcypress is quite resistant to rot. However, most lumber available at lumber yards today is sapwood and is not resistant to rot.
Baldcypress is ideal for wet locations, such as its native habitat of stream banks and mucky soils, but the trees will also grow remarkably well on almost any soil, including heavy, compacted, or poorly-drained muck, except alkaline soils with a pH above 7.5. Locate where the sun will strike the tree on all sides for best symmetrical development. Baldcypress is relatively maintenance-free, requiring pruning only to remove dead wood and unwanted lower branches which persist on the tree. It maintains a desirably straight trunk and a moderately dense canopy and does not form double or multiple leaders as do many other large trees. Find out more about bald cypress here.
Viburnum obovatum and cvs. (Walter’s viburnum)
Walter viburnum, in the opinion of some nursery growers, is the very best viburnum for use in central and south Florida. Unfortunately, it is not widely available. It is a shrub or small tree that can grow to a height of about 25 feet. However, there are forms of this plant that are upright, spreading, weeping, or dwarf. It is difficult to determine which form you are buying by simply looking at the plant. The only way to determine the ultimate height and shape of the plant is to know the original source of the plant material. A reputable nursery will know the characteristics of their plants. The evergreen leaves of walter viburnum vary from very small to medium sized, glossy, leathery, and dark green. They are also fragrant when crushed. The winter or spring flowers occur in small, convex cymes held at the branch tips before new growth emerges. Flowers can cover the plant with white blooms for about 2 or three weeks. The fruits of this plant are small drupes that turn from red to black during maturation.
Walter viburnum may be utilized in the landscape as a fine-textured, clipped hedge or tall screen. Small leaves make it a great candidate for shearing into a topiary, espalier or formal hedge. Older specimens can be trained into small trees with several trunks. Nurseries can also train young plants to grow in this manner.
Walter viburnum will grow well in a site that receives full sun or shade. It is native to acidic wetland forests that are frequently inundated for a period of time during the year, but it tolerates a broad range of growing conditions including moderate drought. Check out this article for more information.
Viburnum odoratissimum (sweet viburnum)
Large, leathery, dark green, glossy leaves and clusters of extremely fragrant, small, white flowers, completely covering the plant in springtime, make Sweet Viburnum a longtime landscape favorite. The large, dull green leaves form a moderately coarse texture. For some reason, it has fallen out of favor as a small tree in recent years. This adaptable tree should be `rediscovered’ by landscape architects and others specifying small trees for urban and suburban landscapes. Often used as a screen or clipped hedge, its dense, spreading, evergreen habit makes Sweet Viburnum suitable for use as a small tree, reaching 25 to 30 feet tall and wide at maturity, with a dense, multibranched, rounded canopy. The flowers are often followed by small, red berries which turn black when ripe and are moderately showy.
Sweet Viburnum grows quickly in full sun or partial shade on a wide variety of soils. It is tolerant to drought, holding up very well in unirrigated landscapes once established. Relatively maintenance-free, Sweet Viburnum grown as a tree will require pruning to control size and shape. A nice, neat, compact canopy develops without any training. Interior sprouts and branches need to be removed to make the trunk show. Only lower branches need removal to allow for pedestrian and vehicle clearance beneath the crown. This would be a good tree for planting along a street where power lines or other obstructions limit overhead space. Nurseries should be encouraged to grow this adaptable plant as a tree form in addition to the shrub form commonly available. It can be trained to one trunk or grown as a multi-stemmed specimen. Find out more here.
Viburnum odoratissimum var. awabuki (awabuki viburnum)
Large, leathery, medium to light green, highly lustrous leaves and clusters of extremely fragrant, small, white flowers, completely covering the plant in springtime, make Awabuki Sweet Viburnum a plant with great potential. The shiny leaves are quite distinctive from the dull, dark green, blunt-tip leaves of the species. For some reason, the species has fallen out of favor as a small tree in recent years, but it is often used as a screen or clipped hedge. Its dense, spreading, evergreen habit makes Sweet Viburnum suitable for use as a small tree, reaching only about 15 to 20 feet at maturity, with an open, multibranched, rounded canopy. The flowers are often followed by small, showy red berries which are highly ornamental and turn black when ripe. This is a small tree which should be tried, and some nursery operators are beginning to grow it. Thirty-year-old plants grow to about 18 feet tall and wide.
Sweet Viburnum grows quickly in full sun or partial shade on a wide variety of soils. Relatively maintenance-free, Sweet Viburnum grown as a tree will require only occasional pruning to control size and shape. This would be a good tree for planting along a street where power lines or other obstructions limit overhead space. Read more about this variety in this article.
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