Florida, known for its stunning landscapes and rich biodiversity, is unfortunately facing a growing ecological threat – invasive plants. While many of these invasive species may appear innocuous at first glance, they are quietly reshaping Florida's natural environment and causing a host of negative impacts.
Invasive plants are non-native species that, once introduced to a new environment, rapidly proliferate and outcompete native vegetation. Florida's subtropical climate and diverse ecosystems make it a particularly vulnerable target for invasive species. While some invasive plants were initially introduced for ornamental or agricultural purposes, they've since become ecological time bombs.
How are plants assessed for their invasive status? There are a few main organizations in Florida that I use for reference on the invasive status of plants. However, there are also some other resources available.
All three of these organizations are useful tools in helping gardeners identify and manage invasive species in Florida. Plants are assessed and placed into categories based on factors created by these organizations. The goal is to have a set standard to measure the probability that a plant is, or will become, invasive.
Category I Invasive Plants are "when they are altering native plant communities by displacing native species, changing community structures or ecological functions, or hybridizing with natives. This definition does not rely on the economic severity or geographic range of the problem, but on the documented ecological damage caused." - definition provided by FISC
Category II Invasive Plants are "plants have increased in abundance or frequency but have not yet altered Florida plant communities to the extent shown by Category I species. These species may become Category I if ecological damage is demonstrated." - definition provided by FISC
Some organizations even have a Category III which is commonly defined as "Caution", or "thought to become invasive".
Assessments are not just done one time. Depending on the organization, they can be done every 2 years or up to every 10 years.
Now, I want to take the time to address the difference between INVASIVE and AGGRESSIVE. I see these two terms used incorrectly on social media. INVASIVE, as we have discussed, means a plants establishment poses threats to the area's native species and the area's ecological functions. Basically, they are altering the area's native ecosystems. AGGRESSIVE, is a discription of growth habit. It has nothing to do with altering ecosystems.
Mexican Petunias, Ruellia simplex, is an invasive species in Florida. It is also aggressive. But what makes it invasive, is it has a direct impact on the native ecosystem. One of the most significant impacts is the hybridization of Mexican Petunias with the Florida Native - Wild Petunia, Ruellia caroliniensis.
On the other hand, Sunshine Mimosa, Mimosa strigillosa, is a florida native ground cover that spreads rather rapidly. This would be called an aggressive growth habit. However, it is not considered invasive. This is because it is a Florida native that does not alter the native landscape.
Now that we know some definitions and the methods of classification, lets take a look at the negative impacts invasive plants can have and why we should care.
Disruption of Native Ecosystems: Invasive plants pose a severe threat to Florida's native flora. They can monopolize resources such as water, nutrients, and sunlight, effectively choking out native species. This not only reduces the diversity of plant life but also threatens the many animals that depend on these plants for food and shelter.
Alteration of Fire Regimes: Some invasive plants, like Brazilian pepper (Schinus terebinthifolius) and Australian pine (Casuarina equisetifolia), are highly flammable and can drastically change the natural fire regimes in Florida. Increased fire risk threatens both native plants and human communities.
Impact on Waterways: Invasive aquatic plants, such as hydrilla (Hydrilla verticillata) and water hyacinth (Eichhornia crassipes), clog waterways, impairing navigation, and interfering with the native aquatic ecosystem. They can also reduce dissolved oxygen levels, harming fish and other aquatic life.
Economic Costs: The presence of invasive plants can result in substantial economic costs. For example, Brazilian pepper infestations have led to costly control measures, while invasive melaleuca trees (Melaleuca quinquenervia) can impact Florida's forestry industry.
Loss of Biodiversity: As invasive plants proliferate, native plants are often pushed out, leading to a loss of biodiversity. This, in turn, impacts native wildlife, as many species rely on specific native plants for food and habitat. Pollinators are drastically impacted by invasive plants. Non-native "look-alike" like Firebush, Tropical Milkweed, and Lantana camara are not specifically adapted to host and feed pollinators like their native counter parts are. Tropical Milkweed can even alter migration patterns of the Monarch Butterfly.
Human Health Concerns: Some invasive plants, like the Brazilian pepper tree, can cause allergic reactions in humans upon contact. Their presence in urban areas can pose health risks, especially to those with allergies. Plants like this are considered "noxious weeds".
The battle against invasive plants in Florida is ongoing, with agencies, environmental groups, and concerned citizens working to mitigate their spread. Strategies include manual removal, controlled burns, and the use of herbicides. Additionally, education and outreach efforts aim to prevent further introductions of invasive species.
Prevention is obviously a huge measure in combating invasive plant species. Florida gardeners are set up for failure by many nurseries continuing to sell invasive plants. Big box store garden centers like Lowes, and Home Depot mass distribute plants with no regard for invasive status. Other nurseries and growers also continue to sell invasive plants. Many gardeners see plants and assume that if they are for sale, that they have to be safe to plant. Or that they are suitable for the areas they are being sold in. Unfortunately, the sale of plants revolves around money. Most invasive species are sold in high quantities because they are easy to grow and propagate. This makes for easy profit.
Gardeners and landscapers need to take more care to learn about invasive plants in their area. This is applicable to backyard gardeners and commercial landscapers. If we continue to disregard the invasives as a legit threat to Florida ecosystems, we will likely face irreparable alteration and damage.
Next I am going to list some of the most commonly used invasive plants that I personally see throughout Central Florida. This list is not inclusive and species not listed should not be presumed to be non-invasive.
Purple flowering perennial commonly used in both residential and commercial landscaping. Some varieties have white or pink flowers. Native to Mexico, South America. Hybridizes with the Florida Native Petunia - Wild Petunia
Lantana is a prennial plant that comes in a wide variety of colors and growth habits. It has vibrant colors and is easy to grow. This makes it a favorite among uneducated gardeners and landscapers. Native to Central and South America. Hybridizes with Florida Native Lantanas
"This shrub/tree is one of the most aggressive and wide-spread invasive plants in Florida, with over 700,000 acres infested. Brazilian peppertree produces a dense canopy that shades out all other plants and provides a very poor habitat for native species. This species invades aquatic as well as terrestrial habitats, greatly reducing the biodiversity of natural communities. There were two separate introductions to Florida from two regions of Brazil, leading to hybridization of the two populations in Florida and hybrid vigor that contributes to its hardiness." - FISC Brazilian Peppertree profile
Plant instead: Youpon Holly
Golden Raintree - Koelreuteria elegans - FISC Category II Invasive Plant
Golden Raintrees are a staple of the fall season in Central Florida. Around September, the evergreen foliage is complimented with bright yellow blooms that turn to a pinkish red before falling off in late October / November. This fall color, the only fall color in Central Florida, made it popular by landscapers in the 1980's and 90's. However, it's aggressive growth habit has caused it to spread and choke out other species through its dense canopy. Native to Taiwan.
Plant instead: Red Maple, Acer rubrum OR Florida Maple, Acer saccharum subsp. floridanum
Tropical Milkweed - Asclepias curassavica - FISC does not currently have this plant listed as invasive but the University of Florida lists it as potential for invasive status and recommends "caution - manage to prevent escape"
This milkweed grew in popularity as interest in Monarch Butterflies boom in the late 90's. Native to Mexico. In Florida, it grows as a prennial and does not go dormant like native milkweeds tend to do. The most common variety has red/orange and yellow flowers. Another variety comes in all orange flowers which I believe is an attempt by growers to confuse buyers into thinking it is the native Asclepias tuberosa.
The negative impacts of invasive plants in Florida are a stark reminder of the consequences of introducing non-native species to delicate ecosystems. Preserving Florida's unique environment and biodiversity requires vigilance and collective effort to control and manage these invaders. By understanding the gravity of the situation and supporting conservation initiatives, we can hope to protect Florida's natural beauty and ecological balance for generations to come.