Prohibited Plants

Bad plants? How can an environmental agency say that a plant is a pest? Well, there are such plants and they are growing all over Miami-Dade County. It's not really the plant's fault that we consider them pests; after all, they are just doing what they do naturally - growing and multiplying.

• Read the Miami-Dade County code and see the Prohibited Plant Species list

Exotic, or non-native, plants are those species found outside of their natural ranges. Once they are taken out of their natural habitat, either for landscape or agricultural purposes, some exotic species are able to escape cultivation and invade natural areas in their adopted land. Because these plants came from other areas of the world, many times their natural population controls (disease, insects, etc.) were left behind in their native homes and these controls are not present in their new homes.

Here they can monopolize resources, out-compete native plants and even displace native wildlife by adversely altering the habitat. For example, Brazilian pepper greatly reduces biodiversity by forming impenetrable thickets, suppressing beneficial fire and cutting off sunlight to the native understory plants. Even shady hardwood hammocks aren't immune to exotic plant invasion. The most troublesome species in hammocks are vines, which tend to completely enshroud trees and shrubs and cut off light to the understory plants below.

So humans have had to step in and fix the mess they made by manually removing these pest plants - a costly and time-consuming process. Some exotic plants are now a major and costly problem in many of Florida's parks and preserves, and some have caused significant health and economic problems to the citizens of Florida. Over $100 million annually is spent to control exotic plants in the United States alone.

While exotic pest plants are a nationwide nuisance, Florida bears the brunt of the problem with nearly 1,000 documented plant species that have escaped from cultivation - and the numbers are still growing. Not all exotic plants brought into Florida, however, are problems. Most exotic landscape plants stay within their bounds and pose no threat to the local natural environments.

Despite the significant threat of some exotic plants, the invasion into our natural areas has been going on silently and practically unnoticed for many years. Consequently, virtually nothing was being done to halt the spread. Now, however, a growing number of federal, state and local agencies hope to change that. Armed with fire, imported natural controls, chainsaws and herbicides, serious attempts are being made to repel these weedy aggressors from our natural areas.

One thing Miami-Dade County has done is study the types of plants that are causing the worst problems and has decided to make them illegal to "sell, propagate or plant" in Miami-Dade County.