Larval Plant Food - lists
by Joy Stewart
So often the lists of larval plant foods for specific butterflies is the genus only, for example Willows (Salix spp)or Apples (Malus spp). A genus list is a very broad category and includes both natives and non-natives. I know that over thousands of years, evolution has established a link between various butterfly species and the plant species that their caterpillars need for food, and this link is usually with native plants. But does that mean that the non-natives don't work? For example, I have a Japanese willow (Salix integra); is it a good larval food for any butterflies species whose larva feed on Willows? Or for butterflies whose larva like flowering crabapples, can I use the Asiatic crabapples or do I have to limit my plants to native crabapples? I don't suppose there is one stock answer to this question--it may depend on the specific plant and on the specific butterfly! But I would love to know if there has been any research done on this topic--it is an important one for gardeners who are trying to attract butterflies.
Great question....I am not an expert, but here are my thoughts.
I checked my book and as you suggested it just lists "willows" as a host plant for Western Swallowtail Butterflies. It might be worth a try to use Japanese willows even though the "local" butterflies might be more accustomed to local varieties. It would be interesting if my readers reported on their local favorite host food plants :)
In my backyard the tropical milkweed (obviously NOT a Minnesota native) is the favorite over the native Swamp Milkweed. Also, I have used parsley which is not a native to attract black swallowtails.
Oftentimes, native plants are much more "nectar-rich" than hybrid varieties. Although there are a few annuals that are favorites, too (i.e. zinnia, pentas, heliotrope, etc.)
Hope my rambling helps.