If you weren't among the hordes of people here last weekend to hear me talk about butterflies, this blog entry is for you! (If you WERE among those hordes, you'll know how funny that intro. sentence was!)
The main gist of my talk was that attracting butterflies to your garden needs to go beyond providing flowers for butterflies. Butterfly gardens need to include trees, shrubs, and plants that can serve as food sources for baby butterflies (aka, caterpillars). Many gardeners are geared towards the end game only on the butterfly spectrum, but that is a crucial mistake.
What are Host Plants?
Many butterflies can only reproduce on one, or very few, species of plants with which they have a specific relationship. If those plants are not available in the landscape, the butterflies cannot reproduce, and we will not have those types of butterflies. Trees and shrubs support the largest numbers of butterfly species, as a general rule, although there are some butterflies that have herbaceous plants (perennials) as hosts. If you have lots of butterflies in your flower garden, you probably have a nearby wild area to thank for them. Most of the host plants for butterfly caterpillars are actually trees and shrubs, and many of those species of trees and shrubs are not common landscape plants anymore. Landscapers install, and garden centers recommend, plants that are quick-growing, easy to sell and establish, and new and exciting. These are often non-native plants, and many of them do not have any established relationships with butterfly caterpillars.
Insects and caterpillars cannot adjust quickly to a fundamental change in the plants in the landscape around them. They have co-evolved with those plants over millennia to be able to eat them and/or reproduce on them. When the plants in the landscape are replaced with primarily non-native plants, wildlife – including butterflies – directly suffers.
What are Nectar Plants?
Adults – butterflies - eat nectar from flowers. Nectar is similar tasting across plant species, so butterflies can take nectar from a wide variety of flowers. They are not limited when they are adults in their choice of food, in the same way they are when caterpillars. Butterflies prefer to feed on flowers that occur in tiny clusters, because there is a great abundance of nectar. Some examples are milkweed, Joe Pye Weed, mountain mint, asters, and purple coneflowers. Butterflies generally prefer to drink the nectar of native plants. However, they will also drink nectar from non-native plants, including butterfly bushes.
But, lest this be seen as an endorsement of butterfly bush, let me say in no uncertain terms that there are big problems with this pretty plant! They are on the watch list for invasive plants in Pennsylvania, due to their tendency to seed around, and displace native plants. Butterfly bushes are not host plants for any known species of butterfly. This means they are only good for butterflies when they are adults. Butterfly bushes may be covered with butterflies, but if native plants are nearby, the butterflies will usually prefer those plants. However, faced with a butterfly bush and few other food sources, the butterflies will drink the nectar from the butterfly bush. This would be like me, a vegetarian, eating at McDonald's - there's hardly anything to attract me there, but if I was hungry enough, I could eat the french fries. And I do, on occasion.
And it all boils down to...
Your garden should have a combination of host plants and nectar plants in order to support butterflies through all of their stages of growth and development. The nectar plants should have staggered bloom throughout the entire season, to provide food, and keep the butterflies in your garden.
Getting Started with your Butterfly Garden
It’s easy to incorporate key butterfly host plants in your garden.
A great one to try is parsley. It’s a host plant for Black Swallowtail butterflies. It’s a biennial, so it will stay in your garden for two years before dying; it’s cheap to buy; you can plant it among other ornamentals in your garden; and you can share it with the butterfly caterpillars for your meals. This is also a good one to try if space is limited, you garden on an apartment terrace or only have windowboxes.
If you have a shady area of your property that stays rather moist, you could plant paw paw (Asimina triloba). It’s one of only a couple of host plants for the Zebra Swallowtail butterfly.
Fritillaries use violets as their host plants. Violets make a great groundcover in the shade.
If you want to attract monarchs, you need to plant milkweeds on your property. Milkweeds are any plants in the genus Asclepias, some of which are very garden worthy. Monarch populations are in serious jeopardy due to loss of breeding sites. Monarchs make a yearly migration to the forest of Mexico, where they spend the winter. They return to the same spots in the spring and summer. Monarchs are losing habitat because stands of milkweed are being crowded out in many places by purple loosestrife, an invasive plant that thrives in the same conditions as milkweed.
Oaks are host plants for over 500 species of butterflies. Planting oaks on your property is a long-term investment towards having lots of butterflies on your property. The other major butterfly trees, in order, are cherry, willow, birch, poplar, crabapple, and maples.
Switching in native plants for non-native plants is almost always a good thing for butterflies. For example, native switchgrass (Panicum virgatum) is known to support at least 25 species of butterflies as a host plant. Non-native Miscanthus (silver-hair grass) is known to support just 1. I've got a large and very beautiful Miscanthus in front of my house which is going to be on the chopping block come spring, to make way for something more useful and just as beautiful...any takers, stake your claim now!
Also…
This may go without saying, but I'm not the silent type: Never use chemicals in your butterfly garden. Many chemicals used for weed or pest control will kill insects, including caterpillars and butterflies.
Some Additional Resources
"Bringing Nature Home", by Doug Tallamy, Timber Press, Nov. 2007. There's a great butterfly and host plant list at the back of this great book. All of my detailed info. comes from his website, where he is publishing his research on host plants for butterflies and moths: http://copland.udel.edu/~dtallamy/host/index.html.
http://home.dejazzd.com/kgard/bcn/butterflies2009.html:
Thanks to my helper this year, Jan Slater, for bringing this great site to my attention. It's a list of all of the butterfly species that have been actually sighted in Berks County in the last 5 years - much better than the larger, more theoretical lists of butterflies in PA that includes sometimes hundreds of species that may have only been sighted once, 46 years ago, in one county, by someone who may or may not have known what they were looking at. Greatly helpful as a cross-reference to Tallamy's list.
And last but not least, we've started a butterfly list as part of the Sugarbush website, identifying each known host plant that we carry that supports species of butterflies that have been sighted in Berks County, PA over the last 5 years. It's right on our plant list. Happy gardening!
Sunday, August 17, 2008
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