Attracting Butterflies—and the Bt/Butterfly Connection
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Plants That Attract Butterflies
Q. What plants will help attract butterflies and birds to my back yard?
- ---Ken in Suitland, MD
I'm interested in having a small plot of plants next year to attract the caterpillars that turn into butterflies. Do you have any suggestions on which plants to use? Thanks.
- ---Jerry from Chester County, PA
A. Yes, but location is also important. Butterfly gardens should be in an area that receives full sun and protection from strong winds, like in front of a South facing stone wall. If that kind of ideal location isn't available, place the tallest plants on the outside of the patch to create a sheltered area in the center. Adult butterflies also love to drink from a little sandy puddle of water, especially if there's a pinch of salt in the puddle. They also like to sun themselves, and any kind of rock in full sun would make an ideal perch; and be perfect for picture taking!
You probably already know not to use pesticides in your butterfly garden, but it's also important not to place birdhouses, birdbaths, feeders or nesting boxes nearby. Rick Mikula, renowned butterfly breeder and author of The Family Butterfly Book (Story; 2000), warns that birds naturally prey on the winged wonders. So plan to only attract one or the other to a specific area of your property (unless carnage is your idea of a good time). You don't have to choose; just locate bird and butterfly areas on opposite sides of the house.
Now the plants: Rick used to like to say that there are three main plants that attract butterflies: "Butterfly bush, butterfly bush and butterfly bush". But while that plant, whose Latin name is Buddleia, is the absolute best overall butterfly attractor, it also appears on many invasive weed lists. (Which only makes sense, as the plants that attract butterflies tend to be less tidy and weedier in habit than most ornamentals.) As alternatives, Rick suggests you consider Joe Pye Weed (Eupatorium maculatum and E. fistolosum) and Blue Mist Shrub (Caryopteris x clandonensis).
Rick adds that Lantana is also a great attractor. And he can't stress enough that "virtually every butterfly nectars on Milkweed", adding that there are many plants in this big family besides the celebrated Monarch attractor common milkweed (Asclepias syriaca). As examples, he cites Blood Flower (Asclepias curassavica); Butterfly milkweed (Asclepias tuberosa), which is great for dry areas; and Swamp milkweed (Asclepias incarnata), which, as its name implies, thrives in wet spots.
For butterfly gardens in the Northeast, Rick also recommends Cosmos, Mexican Sunflower (Tithonia), Echinacea (aka Purple Coneflower), Shasta Daisies and Zinnia. Down South, he says you can expect great results with Blue Porter weed, Flowering Almond and Star Flower. In the mid-West, Monarda (bee balm), Catnip & Asters are his top choices.
Rick adds that purple, lavender and pink flowers attract the most fluttering flyers; especially if they're strongly scented. "Butterflies have an acute sense of smell," he explains, "and prefer old-fashioned varieties to hybrids that don't have a strong aroma."
And, as Jerry implies in his question, you also need 'host' plants if you want to get them breeding out there. These are the plants that females like to lay their eggs on because the caterpillars that hatch out will stuff themselves silly, and then begin their amazing transformation—with those chrysalises right there for you to see. Swallowtails are the only nice looking butterflies that feed on garden crops, but that's all right; just plant some parsley, dill and carrots for them in a dedicated area. That way, you can host their babies in your butterfly garden and harvest from another set of plants in the main garden. Just hand-pick any stragglers and carry them over to their own neighborhood.
Milkweed, of course, is the most famous host, as it's the essential food plant of the fabulous Monarch butterfly. Some other host plants are pretty nasty weeds, like thistle and nettles, but some are well-behaved native flowers and shrubs.
Q. I use dunks containing Bacillus thuringensis in standing water to kill off mosquito larvae. But some research quoted on the Internet seems to suggest that this bacterium also adversely affects butterflies. Is Bt a safe control? Thanks.
- ---Hannah in Oklahoma City
A. Good news! 'Your' Bt is 100% butterfly safe, Hannah. There are several strains of Bt, and the one you're using, known as BTI, only affects mosquitoes and other biting members of the fly family. It has no effect on butterflies or caterpillars. In fact, the Bts are SO species-specific that you can even use BTI granules to keep a butterfly puddle mosquito-free! The butterfly concerns are solely about another, older type of Bt—known as BTK—which only affects caterpillars, which brings us to…
Q. I recently read a newspaper article that expressed concerns about Bt adversely affecting Monarch butterfly caterpillars. Yet you often recommended its use. Please follow-up on this and reconsider your recommendation of Bt.
- ---Judy in Philadelphia
A. The article you read was about genetically engineered corn that had been altered to contain a form of Bt known as BTK in its pollen; a terrible idea that may well threaten monarch butterflies, as they are known to occasionally feed on the pollen of corn plants. BTK is a natural, soil-borne organism that is deadly to caterpillars that chew on leaves that have been sprayed with it. It was bred into corn to protect the edible part of the plant from the corn earworm, a caterpillar that ruins the tips of attacked ears. But when you genetically engineer something into a plant, it appears in every part of that plant. And in this case that includes the pollen, where it doesn't prevent anything, but may endanger butterflies looking for a little sugar rush. This is but one of 700 or so reasons why genetic engineering is a bad, bad idea.
The non-engineered form of BTK that home gardeners have been spraying safely on their caterpillar-attacked plants for many decades is sold under brand names like Dipel, Thuracide and Green Step. Again, it only affects caterpillars that eat the sprayed parts of the plants. And if you're growing sweet corn, you wouldn't waste any BTK on the pollen; you'd just spray the ear tips, which Monarchs aren't interested in.
The only other plants a butterfly caterpillar is going to eat in the average garden are those swallowtail herbs: Dill, parsley and carrots. The caterpillars that pester broccoli, corn, cabbage and other such crops turn into ugly moths that no one wants to protect. The hornworms that pester tomatoes do become beautiful sphinx moths, so handpick them instead of spraying. Otherwise, using BTK against pest caterpillars won't endanger butterflies in the least.