Bromeliads get a bad rap, and they don't deserve it. These exotic tropicals seem to be on every mosquito-fearing homeowner's blacklist, forever banished from the garden for fear their capacity to hold water provides safe harbor for the blood-sucking pests.
But bromeliads are a delight in a Florida garden and one of the easiest plants you'll ever grow. Incredibly forgiving and adaptable, they're found throughout the world in tropical and subtropical climates. There are thousands of species, from sun-loving bromeliads that thrive in sandy deserts and on rocks in the mountains, to shade-lovers that inhabit trees and the jungle floor.
Several bromeliads are native to Florida; most of them are found in South Florida and are considered endangered. In our area you're more likely to find native bromeliads in the Tillandsia genus, which includes true air plants, which are happy growing in trees. Air plants (epiphytes) absorb water and minerals through their leaves and use their roots merely for anchoring.
Not all bromeliads have little reservoirs at their center. Spanish moss (Tillandsia usneoides) and ball moss (Tillandsia recurvata) are perfect examples. But many exotic bromeliads that produce spectacular blooms have those "cups" or "tanks," and they like a little puddle of water in them now and then. It's even better when organic debris settles in, providing nature's best plant food. But it creates a potential problem: Stagnant water is the perfect environment for mosquitoes to lay their eggs.
Horticulturists have conducted plenty of studies to determine if the plant is indeed a major contributor to mosquito populations and to identify which kinds of mosquitoes favor its tanks. A study by the University of Florida found that of 78 mosquito species in Florida, none were specifically associated with bromeliads. However, under certain conditions, certain mosquitoes can be drawn to bromeliads, primarily the small Wyeomyia mosquito, which is active in daytime but doesn't wander far from its home.
"Bromeliads are very environmentally friendly. Mosquitoes can be a problem, but it's a problem that can be solved," says horticulture agent Pam Brown of the Pinellas County Extension/Florida Botanical Gardens in Largo, which has an extensive bromeliad garden with several thousand individual bromeliads.
Several hundred offshoots, or pups, from the Botanical Gardens' bromeliad collection will be offered for sale May 10 at the Pinellas County Master Gardener Plant Sale in Largo. The annual event is one of the bay area's largest sales, with thousands of low-cost plants raised by volunteer master gardeners who, along with professional horticulturists, will provide on-site plant care and landscaping advice.
Mosquitoes aren't a problem at the botanical gardens because horticulturists there regularly apply a safe bacterial toxin that kills mosquito larvae, says Bob Albanese, a Pinellas County horticulturist. Called bacillus thuringiensis israaelenses (BTI), the product is available in granular and doughnut-shaped pieces at nurseries and online suppliers. Brand names include Mosquito Dunks, Quick Kill and Aquabac. At the botanical gardens, granules are applied once a month with a broadcast spreader, but most homeowners need only a few granules per plant, sprinkled in the cups about every 45 to 60 days, says Albanese, who follows that program with his bromeliads at home in St. Petersburg.
Pinellas County Master Gardener Luis Rey, who grows bromeliads at his home and volunteers at the plant sale, insists mosquitoes aren't a problem. However, he's careful not to cluster the plants, to prevent the accumulation of water. It's also important to regularly remove decaying leaf matter from the plant's cup and adjust irrigation sprinklers so they aren't overwatering.
An inexpensive alternative to BTI can be found in the kitchen cabinet. Just 1 drop of cooking oil placed in the bromeliad's cup will smother mosquito larvae. Use a medicine dropper to apply oil about every 20 days, Brown recommends. Another approach is to simply flush the water regularly with a garden hose, to interrupt the mosquito's life cycle so it can't reproduce.
One of the biggest misconceptions about bromeliads is that they are the culprit for mosquito attacks morning, noon and night. Not so, says Albanese. "If you are getting bitten at night, they are coming from somewhere else," he says. That's because the Wyeomyia mosquito flies only during the day, and it doesn't travel more than 50 feet from its host plant. If mosquitoes are a problem in your yard, stop blaming bromeliads and start looking for standing water in other sources, such as open containers, a much more likely breeding ground for those irritating pests.
Yvonne Swanson is a freelance writer in St. Petersburg and a master gardener for Pinellas County.