At a local native plant sale not too long ago, I overheard a customer conversing with a volunteer who was helping her find trees and shrubs for her landscape. When the customer said that she “only chose plants with ‘high wildlife value’”, I cringed.
I know that might strike some people as an odd reaction coming from someone, like me, who is a passionate advocate for using more native plants because of their ecological benefits. So let me give you a little context.
In Maryland – where I live – virtually every native plant aficionado eventually ends up owning a copy of Native Plants for Wildlife Habitat and Conservation Landscaping: Chesapeake Bay Watershed. This publication of the U.S. Fish & Wildlife Service contains information on over 400 species of plants native to the Chesapeake Bay watershed region. A print version can often be found for sale by non-profits, but it is readily available online (both on the National Park Service website as PDF and HTML, and in database form on the Lady Bird Johnson National Wildlife Center website).
I mention this guide because it is a standard reference for plant-sale shoppers, including the customer I overheard, and one feature of the guide is that some (about 15-20%) of the plants are indicated as having “high wildlife value”.
But the definition of “high wildlife value” used in this guidebook and others is arguably incomplete and out of date. It was originally embraced by the United States Department of Agriculture in the 1930s as part of their efforts at encouraging farmers to use native plants for erosion control. The USDA praised certain plants as having “high wildlife value” based, it seems, largely on the value of the plants to game species: essentially birds and mammals.
For example, Clarence Cottam’s 1936 book The Place of Food Habits Research in Wildlife Management presents the concept of wildlife value in this relatively narrow context:
“. . . . the creation of such an environment that the maximum of food and cover is available at all seasons of the year for the particular birds or mammals considered.”
This is essentially the background on which the USFWS guide ultimately depends: “(t)he notation “high wildlife value” is based mainly on the value of the fruits, seeds and/or nectar used as food for wildlife. . . .”
In all fairness, the guide was compiled nearly a decade ago, and even today many of us are still grappling with how to integrate the various ways in which native plants can be beneficial to ALL forms of wildlife. As we become increasing aware – thanks to the work of Doug Tallamy and other scientists – that herbivores are critical component of our food web this archaic reliance on fruit value seems, well, quaint.
For example, Native Plants for Wildlife Habitat and Conservation Landscaping: Chesapeake Bay Watershed lists only one sedge, no grasses, and no wildflowers as having “high wildlife value”.
Why not Goldenrods (Solidago) or Asters? These wildflowers are each a larval host for over 100 species of native butterflies and moths.
Or Switchgrass (Panicum)? Switchgrass is host to two dozen species of butterfly and moth larvae and a critical refuge for many other insects – like fireflies.
Or Milkweed (Asclepias)? Although Milkweed species are only larval host to a dozen different species of butterflies and moths, some of those (like the Monarch) are entirely dependent on Milkweed.
Or Purple Coneflowers (Echinacea)? This plant hosts even fewer varieties of butterfly larvae, but I cannot imagine a better seed source for goldfinches in an urban garden.
These, and many other plants, play critical roles in our ecosystems that go far beyond merely providing fruit or seed to be consumed by animals that people like to hunt. Although I am quite encouraged at the growing awareness on this front, I would like to see a more modern definition of “wildlife value” work its way into common usage. In the meantime, those of us who advance the native plant cause may have to do a little homework on our own and educate our friends with what we find.
I mentioned Doug Tallamy earlier, and I encourage readers who are comfortable using spreadsheets to visit the landing page for his study on larval hosts. A fairly complete list of plants, and the number of species of lepidoptera these plants can support, is there to be downloaded.
The poor customer who started this story was, I’m afraid, building an incomplete habitat because she was dependent on a resource that used an incomplete definition of “wildlife value”. The more we can respect the many various ways that our native plants are part of the ecological whole, the more we can truly achieve gardens with “high wildlife value”.
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