Don't let monsters take over your yard

Some species grow way too fast, spread much too far

dhawkins@keysreporter.comMay 26, 2008 

The Keys climate encourages some plants to grow beyond expectations.

Despite rocky soil and a long dry season, some houseplants spread wildly if they get outside. Trees from tropical regions can grow faster and bigger than Keys homeowners might want. Some common landscape plants have taken over yards and natural areas, which threatens native habitats and animals that depend on them.

The following is a look at several common plants that local experts and experienced gardeners say can turn into monsters.

Scaevola (Scaevola taccada)

Scaevola (usually pronounced “skuh-vo-luh”) is a shrub with light-green fleshy leaves and small white flowers. You can find it along many beaches and seawalls; one common name is beach naupaka. It might seem to be perfect for planting along sandy-salty Keys shorelines. If only it would stay in bounds.

People involved in protecting natural areas say that, among common landscape plants, Scaevola is one of the worst for the Keys natural environment. It can give homeowners headaches too.

“I’ve seen [it] started as little foot-tall plants, and now they’re huge mounds,” said Kim Gabel, environmental horticulture agent with the Cooperative Extension Service in Monroe County.

Small Scaevola patches usually become “giant,” according to Chuck Byrd, former land stewardship coordinator with The Nature Conservancy in the Keys.

Byrd pointed out that there is a native Scaevola species, and it behaves itself. The leaves of the native species (Scaevola plumieri) are thicker and “chunkier” than the exotic species, whose leaves are floppy by comparison. Berries of the native plant, which is also called “Inkberry,” are black, while berries of the exotic species are white.

It’s easy to find the non-native Scaevola for sale, even though it’s listed as a Category I invasive, the worst type on the list of environmental troublemakers compiled by the Florida Exotic Pest Plant Council.

While the native Scaevola “plays fair, is balanced, and fits in with the Keys environment well,” the exotic variety, probably brought to Florida from Hawaii, “tends to form super-dense hedges,” Byrd said.

“If you’re losing square footage in your yard due to a Scaevola-like plant, chances are it’s exotic,” he said. Even if you think, “I don’t mind this monster hedge taking over the yard,” Scaevola seeds float. Thickets are crowding out native plants in the backcountry and beaches in Florida.

Snakeroot (Sansevieria hyacinthoides)

This plant goes by several names, including Mother-in-Law’s Tongue, Bowstring Hemp and Snakeroot. Green, strap-like leaves marked with lighter mottling have made it a popular potted plant. You can buy it anywhere, and it’s hard to kill. And like Scaevola, it can take over your yard and has been spreading into native habitats in the Keys. It’s designated a Category II invasive on the Pest Plant Council’s list.

Karen Strobel, an environmental consultant in the Upper Keys, considers it one of the worst invaders of natural areas here. People are “surprised and pleased to see how well the houseplants that struggled up north do down here,” she noted. Many Snakeroot thickets have started from plants thrown out of their pots.

“Boy that just goes hog wild,” Gabel, of the extension service, said of Snakeroot. How can you get rid of it? “Basically, you’re just trying to dig up as much as you can,” she said.

Byrd toiled with volunteers to clear natural areas invaded by snakeroot.

“There have been times on work parties...where both husbands and wives tell us the name ‘Mother-in-Law’s Tongue’ is appropriate.”

In hammocks, “nothing else can grow” where Snakeroot gets established, Byrd said. “It completely takes over the low vegetation in the hammock. We’ve been working on some patches for years in Crane Point Hammock. Each little piece of root can re-sprout,” which makes it so difficult to eradicate, he said. “We get a lot of calls from homeowners asking ‘How do I kill this thing?’”

Be prepared for undesirable tenants, too. “There are always snakes and spiders” in Snakeroot thickets, Strobel said.

Problem trees

More than a few plants you can find at nurseries or sprouting in your yard can grow way too big. Not all of these are imported (exotic) plants. A few native trees, including Strangler Fig (Ficus aurea) are not good choices for small yards.

As its name suggests, Strangler Figs can swallow other trees after sprouting in their branches. They also drop messy fruit, have brittle branches and sticky sap.

Autograph Tree (Clusia rosea) can grow to have a huge trunk and above-ground roots the size of large branches. Royal Palm, (Roystonea elata) another native, is stately and beautiful, but would be a monster in most Keys yards at full height (50 to 80 feet or more).

Most natives, though, are a better bet than almost any exotic import. If you do select exotic plants, descriptions like “lush” and “fast-growing,” should make you think, “trouble?” Tropical trees might start small, but many want to grow into jungle.

  • Consider Rubber Plant, also called Rubber Tree (Ficus elastica). It has big, thick leaves and grows fast into an enormous shrub-like mass, nearly as wide as tall.

  • Local experts say everyone should also avoid Schefflera (Schefflera actinophylla), also called Umbrella Tree. It’s fine as a houseplant but a big problem outdoors. Scheffleras grow large, with weak branches, and they constantly drop huge leaves that never decay. Schefflera is another species that spreads easily and has invaded natural hammocks; it’s designated as a Category I invasive pest.

    Finally, there are some popular trees that might not be typical monsters, but do cause problems. If you want to help protect native species and resources, consider carefully before planting these:

  • Sapodilla: (Manilkara zapota): A medium-sized fruiting tree planted by many Keys homesteaders, it’s now recognized as an invader (Category I) of natural areas in the Upper Keys. It’s also pretty messy in a yard.

  • Coconut palm (Cocos nucifera): Supposedly the signature tree of paradise, people who do their own yard work usually figure out that coconuts make a lot of waste and can be dangerous. They’re not native. They dangle bowling ball-size (and weight) nuts over your yard, and drop huge fronds that you have to cut up to get rid of. Native Thatch palms (Thrinax radiata or Thrinax morrisii) are better choices — smaller overall, with pea-sized seeds, and smaller, fan-shaped fronds.

  • Yellow Elder (Tecoma stans): A small tree, attractive for its showy yellow flowers. But these trees are seed-spewers, which causes offspring to sprout like weeds. The trees are starting to invade natural areas, according to Gabel. Also, the weak wood breaks up easily in storms.

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