Field Guide to the Hardwood Hammock Nature Trail By Ryan Vogel Introduction The FIU Nature Preserve is a managed site, developed to reproduce communities indigenous to the Florida Everglades. It was first dedicated a Preserve in 1978 by the FIU Administration and has since achieved various other certifications through the National Wildlife Federation, the North American Butterfly Association, and Fairchild Tropical Botanic Garden. The FIU Nature Preserve is home to 248 plant species including 13 threatened species, 9 endangered species, and 4 endemic species, endemic meaning that these species are present nowhere else in the world but southern Florida. It also provides habitat for approximately 95 species of birds, 45 species of butterflies, 20 species of reptiles and amphibians, and several small mammals as well. This field guide is an attempt to present an overview of the major plant species found in a hardwood hammock community. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 1. Shortleaf Fig (Ficus citrifolia) Figure 6 – Fruits on long stalks Figure 7 – Fruit on stalk with mutualistic wasps inside Although Ficus trees can be seen all throughout Miami-Dade County along roadsides and in parks, most of the commonly planted Ficus are exotic; there are only two species that are truly native to southern Florida. One of which is the notorious Strangler Fig (Ficus aurea) and the other is the Wild Banyan Tree or Shortleaf Fig. The easiest way to tell the two species apart is by their fruit; F. citrifolia has its fruit on a small stalk or peduncle, as opposed to F. aurea whose fruits are borne sessile (attached directly to the branch). The shortleaf fig is an evergreen tree with one solitary trunk unlike its close relative F. aurea which has a more irregular trunk form, often growing as a vine in its earlier stages. The tree has alternate, entire leaves that are 5 – 11 cm long and 3.5 – 9 cm wide. The leaves are dark green, leathery, and smooth. The most significant difference between this tree from the closely related strangler fig is that the fruits are borne on obviously elongated stalks, not sessile. 2. Sabal Palm (Sabal palmetto) Figure 8 – Tree form Figure 9 – Persistent leaf bases on trunk Figure 10 – Costapalmate leaf Figure 11 – Leaf fibrous hairs Here is the Florida state tree, the Sabal Palm. This is one of the most common palms in southern Florida due to its ability to grow in very diverse habitats (pine rocklands, hardwood hammocks, and wet prairie communities). It is one of only 8 native palms in the state of Florida, and one of only four that exist in the Everglades. Sabal palms are straight trunked trees which do not grow more than 50cm in diameter or 18m in height. They have unique costapalmate, fan shaped leaves (1 – 2 m long) which are deeply divided and conspicuously V-shaped; these are key distinguishing factors in identifying this species. Each leaf has numerous fibrous threads suspended from the segment margins. The lead petioles can be up to 2 m long and the trunk will often be covered with these persistent leaf bases for years to come; however just as often you will see this tree with no persistent leaf bases, so this is not a great identification factor. 3. Live Oak (Quercus virginiana) Figure 12 – Stout, wide canopy Figure 13 – Short trunk and immensely horizontal branches on mature trees Figure 14 – Revolute, stiff, dark green leaves Figure 15 – Light brown to black (when mature) acorn Here is a very typical hammock species, the Live Oak. It is the southernmost reaching oak in all of the United States, with its range extending well into the Florida Keys. Although these trees will never grow to be that tall (20 m), they do become very widespread, bulky individuals as they age. Typically they have a short central trunk, with rough bark, which divides into several large branches within a few meters from the ground. These trees have alternate, simple, entire, leathery, and stiff leaves about 2 – 15 cm long and 1 – 5 cm wide. The leaves are dark green and shiny above and pale gray and tomentose below. 4. Dahoon Holly (Ilex cassine) Figure 16 – Tree/leaf/fruit growth habit Figure 17 – Leaf tip often with spines Figure 18 – Fruit form 5. Ferns Figure 19 – Brackenfern Figure 20 – Swamp fern Figure 21 – Resurrection fern 6. Gumbo Limbo (Bursera simaruba) Figure 22 – Tree form Figure 23 – Copper peeling, flaky bark These are very iconic hammock species that can grow to be quite large when given the time and the right environment. However, they are usually medium sized deciduous trees growing to about 20 m in height with a slightly spreading canopy. The copper-colored resinous bark has the aroma of turpentine and can often be seen flaking off to reveal a brilliant green under layer. This peeling superficially resembles the skin of a visitor to Miami when they have not applied sufficient sunscreen, giving it the local name of the “Tourist Tree”. 7. Fire bush (Hamelia patens) Figure 24 – Leaf/stem/flower color This is a large evergreen shrub that grows to about 5 m in height and has a wide spread. The leaves are opposite or whorled with 2 – 7 leaves at each node and interpetiolar stipules at each node as well. Each leaf is simple, entire, elliptic, 5 – 15 cm long, 2 – 8 cm wide, and the leaf blades are often reflexed upward from the central vein. The leaves, veins, and petioles have a reddish tint while the tubular flowers are bright red/orange, which is why it gets its name Fire bush. 8. Slash Pine (Pinus elliotti) and Coontie (Zamia pumila) Figure 25 – Tree form with clustered needles Figure 26 – Bark color and form Figure 27 – Cone form and needles clustered at branch tip Southern Florida is home to the last remaining fragments of pine rockland habitat; a highly endangered and endemic ecosystem that is found nowhere else in the world. A healthy pine rockland environment has a canopy that is dominated by slash pine (Pinus elliotti), the pines you see here above you. Due to timbering interests and development, very few large stands of pine rockland still remains today. Slash pines are evergreen conifers with long needles (13-30 cm) arranged in fascicles of 2 or 3. The ovulate cones are 7-16 cm long. A mature tree will grow to be 18-30 m in height and have a trunk diameter of up to 65 cm. Slash pine occurs as far west as Louisiana, as far north as South Carolina and south throughout Florida, the Keys, and the Caribbean. Pinelands usually have a very open understory due to high occurrence of fire which eliminates many understory species except those that are well adapted to fire like the coontie. Coontie is a small shrub that was at one time an important food crop in southern Florida, which almost led to the species’ extinction. This plant is a cycad, which means it has special reproductive cones known as strobili. Cycads are a very old family of plants that have been around since the age of the dinosaurs. However, due to the lack of fire here in the Preserve, much of the ecosystem has succeeded to a tropical hardwood hammock community. Succession is the natural replacement of one plant community by another, a process that takes place over time with the lack of disturbance. Figure 28 – Coontie growth habit Figure 29 – Leaf color and growth habit Figure 30 – Coontie reproductive strobili 9. Myrsine (Myrsine cubana) Figure 31 – Growth habit and leaf color Figure 32 – Cauliflorous flower habit A plant adapted both to open places and shady hammocks is the myrsine. It is often a pioneer plant invading recently burned areas. Myrsine is a hardy survivor of fires by means of stump sprouts. Along the branch, below the leaves, are located clusters of small flowers or black fruits, which are borne sessile, along the stem. These are found only on the female plants. You may notice small, dark bumps on the stems of the myrsine. These are lobate lac scale insects, Paratachardina lobata, native to India and Sri Lanka. These were first documented in South Florida in 1999, and since then has been found to infest at least 39 different native plant species. Some more susceptible species include: Cocoplum, Wax Myrtle, Red Bay, Strangler Fig, Wild Coffee, and of course Myrsine. Currently, research into biological controls is being conducted in order to eradicate this pest. 10. Red Bay (Persea borbonia) Figure 33 – Leaf color and growth habit Figure 34 – Fruit habit Figure 35 – Lanceolate leaf shape Red Bay is a common tree in mature hammocks, but they especially like wetter sites, which is why you can find them growing along the margins of swamp islands in the Everglades. The leaves are glossy with a pale underside. Red Bay is related to several economically important food plants such as the avocado, camphor, and cinnamon. Like Bay leaves used in cooking, the leaves of Red Bay emit a spicy aroma when crushed. This is an evergreen shrub that grows to be a small tree no larger than 20 m in height. It has alternate, simple, entire, lanceolate, 2 – 15 cm long and 1.5 – 6 cm wide leaves that when crushed give off an aromatic fragrance similar to that of the culinary bay leaf. The fruits are rounded dark blue drupes that get to be 1.2 cm in diameter. 11. Pidgeon Plum (Coccoloba diversifolia) Figure 36 – Leaf color and habit 12. Solution Hole and Pond Apple (Annona glabra) Figure 37 – A typical Everglades solution hole Figure 39 – Leathery, dark green leaves Figure 38 – Pond apple tree habit Figure 40 – Fruit resembles commercial apples Solution holes are formed from detritus or decaying pant material, which in turn lowers the pH of the water and soil in a particular area. This acidified water/soil is then able to eat away at the basic limestone rock substrate, developing a hole or depression in the rock. Pond apple is a common freshwater wetland species found in southern Florida. It really thrives in wetlands and produces fruits that are similar in shape and size to our commonly cultivated apples. The fruits have a very bitter taste and begin to turn yellowish when they are ripe. 13. Bitterbush (Picramnia pentandra) Figure 41 – Shrub growth habit Figure 42 – Leaf color and form Bitterbush is a small evergreen tree and typical understory plant; rarely reaching its full potential of 6m in height. It has alternate pinnately-compound leaves that are 20 - 36 cm long with 5-9 slender pointed leaflets. During the dry season, the leaves often turn red. The female plant will produce red berries. It is state-listed as endangered and is endemic to Miami-Dade County. Each leaflet is entire, ovate, with an acuminate apex, 5 – 10 cm long and 2 – 5 cm wide. 14. Jamaican Dogwood (Piscidia piscipula) Figure 43 – Revolute leaves and papery fruit pods These trees are deciduous, have twisted branches, and thin gray bark. They can grow to about 15 m tall. They have alternate, oddly-pinnate compound leaves (10 - 23 cm long), each with 5 - 11 leaflets. Each leaflet is grayish green and 4 - 10 cm long with wavy, often revolute margins and obvious primary and secondary veins. The fruits are light brown pods, 7.5 - 10 cm long and 2.5 - 3.7 cm wide, each with four papery wings. 15. Wild Tamarind (Lysiloma latisiliquum) Figure 44 – Leaf habit Figure 45 – Flower habit If you look up and to your left you will see a few very large Wild Tamarind trees looming overhead. In this more open setting, rather than deep inside a hammock, the tree develops a spreading umbrella-like crown. This characteristic makes them excellent street and shade trees. Beneath the lowest pair of leaflets you will find nectar glands which secrete nectar while the leaves are young. Although, this tree only grows to about 10 or 20 m in height, they are known to develop a wide canopy spread. The trunk has light gray or whitish bark. With alternate, bipinnately compound leaves with an overall length from 10 – 18cm long. Each leaf having between 2 and 4 pairs of pinnae and each of those pinna with 8 – 15 pairs of leaflets. The miniscule leaflets are 8 - 15 mm long, 3 – 5 mm wide with an elliptic or oblong shape. The fruits are flat pods, 6 – 10 cm long, 2 – 4 cm wide, and usually remain on the tree throughout the entire year. 16. West Indian Mahogany (Swietenia mahagoni) Figure 46 – Compound leaves Figure 47 – Asymmetrical leaf margins Although many know Mahogany as a valuable piece of timber, these trees hold an important ecological role as well. These evergreen trees only establish once a hammock has achieved a sufficient age and level of maturity. They grow to about 15 m in height with rough, dark brown, coarsely furrowed bark. Often they have a buttressed base as well as wide spreading branches. The leaves are alternate and even-pinnately compound, typically with two to four pairs of leaflets per leaf. Many mahogany leaflets curve backwards toward the base of the rachis, with one side of each leaflet seeming slightly shorter than the other. The fruits are very large, conspicuous, upright, egg-shaped capsules. The fruits split into five parts from the base and rely on the wind to transport their winged seeds.