I mentioned in a previous post that I only recently learned that my practice of carting away leaves and old plant stems in the fall is likely contributing to the decline of the local butterfly population (see “Life in the Leaf Litter,” “Six reasons to NOT clean up the garden this fall,” and the related “4 Reasons Not to Rush the Spring Garden Cleanup”). This post is intended to provide links to more information on the topic of host plants for local fauna.
First, some terminology.
“A [North American] native plant species is one that occurs naturally in a particular region, ecosystem, and/or habitat and was present prior to European settlement” (definition from Wild Ones).
A native plant grown from seeds or divisions is a straight species native plant.
A nativar is a cultivar of a native plant. (A cultivar is a plant type produced by selective breeding.) Plants are selected for reproduction on the basis of certain characteristics “to the exclusion of the inherent variation found in nature” (Wild Ones).
An obligate larval host plant is a plant that is required by an insect species. The adults might take nectar from a variety of plants, but they will lay their eggs on, and the larvae will feed on, only one or a few species (e.g., monarchs and milkweeds).
According to a recent article in the Star Tribune, planting “for the express purpose of feeding insects” is “a seismic shift in gardening.” The article provides a short list of Minnesota butterflies and their preferred host plants.
A post from the University of Minnesota Extension talks specifically about little bluestem (Schizachyrium scoparium) and the butterfly larvae known to feed on this native grass, including Dakota skippers and several other species of skippers. Interestingly, the only photo in the post shows a cultivar of little bluestem rather than the straight species.
Are cultivars/nativars as useful to wildlife as straight species? For some opinions on this topic see this article from the Rochester Post Bulletin and this from the University of Missouri Extension, both positive. On the more negative end of the spectrum, see this position statement from the Wild Ones, this article from the National Wildlife Federation, and this from EcoBeneficial.
To learn more about host plants other than milkweeds, start with the Native Plant Finder from the National Wildlife Federation, this article from Minnesota Gardener Magazine, and this list from the U of MN Extension. It’s a short list, but additional links and sources are noted.
If you’re more interested in birds than butterflies, note that “96 percent of all birds need insects as part of their diets at some point in their lives – even hummingbirds. … [H]ummingbirds feed their young a certain kind of native bee, and that bee feeds on a native plant: New Jersey tea (Ceanothus americanus). It’s a 3-foot tall shrub with white flowers that bloom from June through August” (quote from the Minnesota Gardener article in the previous paragraph).
Many of the plants mentioned in the sources listed above are readily available from native plant nurseries. Others are harder to come by. I read in Native Plants of the Midwest by Alan Branhagen that Canada plums “host so many creatures that their foliage can look tattered by midsummer.” Branhagen adds: “The gorgeous flowering cultivar ‘Princess Kay’ has been selected from wild Minnesota stock for superb double flowers equally as exquisite as any oriental flowering cherry but providing no nectar for pollinators” (p. 172).
I thought it would be nice to tuck one of these plants into a corner of my yard, but finding straight species Prunus nigra isn’t easy. ‘Princess Kay’ is available from several nurseries, but the only source of non-cultivar Canada plums seems to be seeds from Gardens North. Do I want to grow a plum tree from seed? As the old saying goes, the best time to plant a tree was twenty years ago. When their seed sales re-open in September, I may just send away for a packet.