The amount of rainwater that hits the roof of even a modest home is astonishing. For a 1,000 square-foot home, runoff from a 1-inch rain can top 600 gallons.
As more gardeners try rain barrels, the marketplace has responded with options both fancy and utilitarian. We bought 55-gallon barrels made from food-grade plastic in Nashville off Craigslist a few years back. The seller had drilled holes, installed spigots, and provided set-in cages at the top plus wide, segmented sections to attach to each gutter downspout.
In late fall, empty, rinse and turn them over. In setting up each spring, rinse the interior and fill to the tap to check for leaks. In cold climates, trapped water can freeze and expand, cracking the plastic. The seal that holds the spigot in place may deteriorate with time and the elements. Some silicone sealer will fix it.
Place rain barrels under high-volume downspouts, close to the house or outbuilding and near garden beds and other areas you’ll use the water. Elevate them on sturdy cinder blocks so a bucket fits under the spigot. We slip a garden hose segment over the tap to direct water to the beds, so a little elevation also goes a long way.
Mosquitos release their larvae in standing water, so rain barrels are mosquito magnets. As a first line of defense, cover openings with fine metal mesh or even old pantyhose.
Still, they will come. Garden experts recommend three separate approaches (try them one at a time though – not all at once).
OIL BARRIER: Add enough food-grade oil to create a slick on the water surface, which stops mosquitoes from releasing larvae. Any that get through won’t survive. A few tablespoons of vegetable oil is enough and won’t hurt your plants.
LARVICIDES: Chemical and microbial control comes in granular or “dunk” form (available from most garden centers). The amount used is based on surface water area. We break each dunk, which looks like a sandy donut, into fourths and toss a piece in each barrel once a month.
FISH: Some gardeners add a goldfish or a few guppies to each barrel. The fish will eat mosquito larvae as soon as they hit the water. But don’t combine fish with either of the other methods – the oil stops the water from being aerated so the fish will die.
To use more than one barrel side-by-side, raise adjacent units higher with extra blocks. With flexible tubing, divert water from the overflow of the highest barrel into the next lowest, and so on, creating a cascade. Depending on the diameter of the overflow on a single-barrel or the one closest to the ground, attach garden hose or other tubing to divert excess water away from the house.
Remember, don’t mix and match mosquito control methods. Try one and use up the water before switching. And if you buy fish, check with the merchant. If the little swimmers do a great job, they may need supplemental fish food.
If you’re using rain barrels, we’d love to hear how yours are working!