Spring-Cleaning in the Nursery

While we do not exactly have a spring season in south Florida, I use the common phrase “spring-cleaning” to denote this particular activity. I initiated an effort to clean out some of the weedy and invasive species that we have growing in our nursery and shade house. We have very limited nursery space to grow seedlings, cuttings and pups from some of our collections, therefore space is at a premium. Last month we obtained new plant specimens from nearby Fairchild Tropical Botanic Garden and last week we received several new arrivals from Montgomery Botanical Center. While we finalize garden planning on where to place these specimens, they may wait in the nursery area for several weeks before being out-planted. By cleaning out the nursery and taking stock of what we have, we can make space for new arrivals, focus on keeping plants healthy, and most importantly, remove invasive species.

I realized that we had several plants that are considered invasive species in south Florida and the Keys, while doing an inventory of our nursery stock. This issue is important to me since I have worked on the land management side of botany and seen what havoc invasive species can wreck on the environment, not to mention the hours spent removing the pests and the amount of tax-payer dollars spent trying, in vain, to control these weeds. While oftentimes these plants are beautiful, if they make it out of gardens and into our natural areas, they become invasive and threaten our native, south Florida species, many of which are already rare. Our Gardens are about 0.5 miles from the nearest natural area to which birds could potentially spread seeds. By having these plant species in our Gardens, visitors may be inspired by their beauty and possibly plant them at their homes, spreading the problem further afield. I would like to inspire people to plant native plants and non-invasive exotic plants. By eliminating the potentially invasive species from our Gardens, we can rest assured.

Among the plants we have removed from our nursery so far are wart fern (Microsorum scolopendrium) and Asian sword fern (Nephrolepis brownii), tropical almond tree (Terminalia catappa), Mexican fan palm (Washingtonia robusta), and cardboard palm (Zamia furfuracea – a cycad). We have begun removing fountain and napier grasses (Pennisetum setaceum/ P. purpureum) from our landscape and are replacing them with native grasses. There are a few specimens of other invasive exotics in the Gardens that we are grappling with: strawberry tree in our fruit garden (Muntingia calabura), arrowhead vine (Syngonium angustatum) climbing up a palm trunk, Governor’s plum (Flacourtia indica) & Brazilian pepper (Schinus terebinthifolius) providing privacy along a property line and actually rooted on the adjacent property, and foundation plantings of Queensland umbrella tree (Schefflera actinophylla) that provide shade and block road noise for guests and have been on the property for over 20 years.

Removing plants from the nursery is one thing, but how do we deal with these mature plants in the ground? To remove a Schefflera is a huge task with a high price tag, and with nothing large enough to fill its place, would leave a gaping hole. When is having a specimen that you can educate the public with more beneficial than removing it? These are some of the tough decisions that botanic gardens must make when potentially invasive species are part of our collections.

Cardboard palm (Zamia furfuracea) ready to be composted. This species has been added to the Florida Keys list of invasive plants due to its tendency to spread from the landscape into natural areas by seed dispersal. It pops up all over our Gardens from existing plantings which we are working on replacing.

A Tropical almond (Terminalia catappa) sapling on its way out. Seedlings of this species pop up throughout the Gardens even though the mature tree was cut down years ago. New seeds may arrive in mulch deliveries, as well.

Wart fern (Microsorum scolopendrium) that has escaped its nursery pot and started to grow along the ground. Watchful botanists in Miami Dade county are adding this plant to the state invasive species list as it is showing up in natural areas. It is not yet invasive in the Keys, and in fact may not become invasive down here since we have a drier climate, but we have many visitors from the metro Miami area and do not want to encourage them to plant this fern.

Asian sword fern (Nephrolepis brownii) specimen. This species is listed as invasive for Central and South Florida and is invading hammocks in the FL Keys. It is also invading nearby pots in the orchid house (see photo below). Ferns can be particularly tricky due to the multitude of spores they release. The Old World climbing fern and Japanese climbing fern (Lygodium microphyllum, L. japonicum) are both major problems in Florida and in several other southeastern states. Since its introduction in the 1960s, Old World climbing fern now covers 50,000 acres of habitat in Florida, literally climbing over every other plant in its path.  

Small sporophyte of Asian sword fern growing in adjacent pots.

On the flip side, botanic gardens may be some of the first places that a new species’ invasive potential becomes known, or a new pest becomes evident. It is then our obligation to spread the word and inform the local extension service and regulatory committees of the threat. Having staff members that are part of a local invasive plant watch group is helpful to stay abreast of developing issues in your surrounding area. It is our duty as botanical gardens to educate the public about these issues and promote the sale and use of local native plants and non-invasive exotic plants.

In the Florida Keys, our local eradication network is called the Florida Keys Invasive Exotics Task Force. This group includes local, state, and federal agencies and non-profit and public utility personnel who are responsible for removing invasive plants from local natural areas like state and county parks. By working with this group and others like it in south Florida (Everglades Cooperative Invasive Species Management Area & Florida Exotic Pest Plant Council) I am able to stay informed and help prevent the spread of invasive exotic species. Publications such as the AlterNatives Plant Guide are a great way to share local knowledge on landscaping and gardening with the public. 

Emily B. Magnaghi

Associate Director