Bad Plants in the Keys

Learn about invasive and poisonous plants in the Florida Keys.

Invasive Exotic Plants

by Diane Marshall

Non-natives or “exotics” are plants that grow outside of their native areas. Such plants are grown around the world in gardens, natural settings, houses and offices. These newcomers become unwelcome when they adapt so well to their new environments, that they begin to out grow and displace native plant and wildlife communities. When they reach that stage, they are considered invasive.

In Monroe County, four exotics have become so invasive in the hammocks, pinelands, and wetlands, that they threaten or endanger 42 native plant species and 27 animal species to the point of extinction. Millions of dollars are being spent to eradicate invasive exotics, and federal and state laws have been passed to restrict their possession, transport and sale.

Australian Pine (Casuarina equisetifoliai), not a true pine, is a large (up to 150 ft.) evergreen tree with rough, peeling, reddish-brown to gray bark. It has long (4 to 8 inches) needles and woody cones with winged seeds.

Brazilian pepper or Florida holly (Schinus terebinthifolius) spreads bush-like up to 40 ft. high and 40 ft. wide, with dense compound leaves that have 3 to 9 inch veined leaflets, a reddish-brown trunk and stems, small cream to reddish flowers in upright clusters, and clusters of bright red oval-shaped fruits.

Asiatic colubrina or Latherleaf (Colubrina asiatic) is a sprawling shrub with dark green 1.5- to 3.5- in alternate, elliptical leaves that have serrated margins and are shiny on top and dull underneath. Its clustered, small (1/16 inch), greenish white flowers produce grooved, fleshy green to brown fruits 1/4 to 1/2 inch that have grayish seeds.

Melalueca (Melalueca quinquenervia) grows a tall (up to 100 ft.) evergreen tree with a thick, smooth, whitish bark that peels in thin layers, exposing reddish bark underneath. Its alternate, simple, grayish-green, lanced shaped leaves (4 inches) smell like camphor when rubbed. White flowers grow in clusters between the leaves. Its woody fruits have hundreds of tiny seeds.

There are several ways to eliminate invasive exotics. Small plants in small areas are best removed by hand. For large areas, backhoes or bulldozers may be more effective. Root removal prevents re-sprouting. Several removals may be necessary if seeds have germinated or if root fragments remain behind.

Herbicides are also effective. Remove the plants and within 1 minute, paint the stumps with Garlon 3a, Roundup Pro or Rodeo. Garlon 4 and Pathfinder II can be applied up to 24 hours after cutting the tree. Basal Bark Treatment is also effective, but it takes a month to kill the tree. Paint a band of Garlon 4 and Pathfinder II completely around the tree about 6-12 in above the ground.

Use care when removing Brazilian pepper and Melalueca. Both can cause skin and respiratory irritation. Also, a free permit is required by the Monroe County Building Department to remove invasive exotics.

Poisonous Plants

by Diane Marshall

Many plants and trees that grow in Monroe County are poisonous if eaten or injurious if touched. The list includes natives and popular ornamentals. However, with a little prudence and familiarity, you can enjoy these plants and keep yourself, your family, and your pets safe.

Start by identifying the plants in your home and yard. If you’re unfamiliar with a plant, make a few notes about the leaf shape, flower, seed and/or fruit. Plants can be identified through using books or the Extension Service. If you are unsure whether a plant is poisonous, wear gloves before touching it.

Be especially diligent if you have children or pets. They are most likely to ingest or touch unfamiliar vegetation, and because of their small size, they are less able to withstand the adverse effect of a toxic substance. Teach older children to avoid eating or touching unfamiliar plants. Keep younger children and pets away from poisonous plants. As a last resort, consider removing the vegetation.

Due to different physiology, birds and wild animals can eat plants, fruits, and seed that are not safe for human consumption. So do not assume that just because they can eat it, you can too.

If someone or a pet shows symptoms of skin irritation after handling plants, wash the skin with soap and water. If there is no relief or if the irritation is severe or spreads, seek medical assistance. When an unknown plant is ingested, watch for signs of vomiting, dizziness, incoherence, diarrhea, or respiratory difficulties. Contact a physician, hospital poison center, or veterinarian immediately. Wear gloves and cut a piece of the plant-- several leaves, the stem, flowers and fruit-- to bring to the doctor, hospital, or vet with you for identification.

Here is a partial list of common poisonous and injurious plants in our area

Allamanda, Yellow (Allamanda cathartica L.) grows as a vine with large yellow flowers. If eaten, all plant parts cause vomiting.

Barbados Nut (Jatropha curcas L.) is a small tree (up to 15 ft.). The seeds contain a purgative and toxin.

Brazilian Pepper (Schinus terebinthifolius) a major invasive exotic tree, spreads bush-like to 40 ft. by 40 ft. It can cause serious skin itching, inflammation and respiratory irritation.

Carolina or Yellow Jessamine (Gelsemium sempervirens) is a woody vine. All parts are toxic.

Castor Bean (Ricinus communis L.) is a small tree. All parts, especially the seeds, are highly poisonous.

Coral Plant (Jatropha multifida) grows as a small tree (up to 20 ft). The seed, leaves, and sap are the most poisonous and irritating.

Crown of Thorns (Euphorbia milii Ch. des Moulins) is a low shrub with thorny stems and branches. The white sap is severely irritating; thorns are dangerously sharp.

Dieffenbachia or Dumb Cane (Dieffenbachiase sequine) usually grown as a 3-6 ft. tall house plant. Juice is toxic and irritating.

Lantana (Lantana camara) is a spreading shrub. All parts are poisonous, especially the berries when they are green.

Mango (Mangifera indica) is a popular fruit tree. A relative of poison ivy, its leaves, juice and fruit can cause a skin rash in some people.

Oleander (Nerium oleander L.) is commonly grown as a woody shrub or hedge, from 5 to 25 ft. tall. All parts, including smoke from burning, are highly poisonous. Ingesting a small amount causes vomiting; eating larger amounts may even cause death.

Oyster Plant (Rhoeo spathacea) used frequently as a ground cover. The leaves are an irritant if touched or ingested.

Pencil Cactus or Milk Bush (Eurphorbia tirucalli L.) grows cactus-like as a tall multi-branched shrub (15 to 20 ft.). The white sap is extremely toxic and irritating.

Poison Ivy (Toxicodendren radicans) grows as weedy vine or shrub. All parts, including the smoke of the burning plants, are severely irritating and poisonous.

Poisonwood (Metopium toxiferum) a tall tree (up to 40 ft.) is easily identified by its gray-brown bark blotched with 8-15 inch watery black spots, alternate compound leaves, and 3-7 shiny, ovate, pointed tip leaflets. It also has tiny, creamy, clustered flowers, and clusters of ½ inch brownish fruits. All parts can cause severe skin irritation.

Rosary Pea (Abrus precatorious L.) grows as a woody vine with alternate leaves. Its seeds are poisonous.