Keystone Native Plants by Region

The concept of keystone plants in horticulture comes directly from ecology research, specifically the work of entomologist Doug Tallamy, whose data -- compiled over more than two decades -- quantifies which native plant genera support the greatest number of caterpillar species, which are the base.

The concept of keystone plants in horticulture comes directly from ecology research, specifically the work of entomologist Doug Tallamy, whose data — compiled over more than two decades — quantifies which native plant genera support the greatest number of caterpillar species, which are the base of most terrestrial food webs. Per Tallamy and Shropshire's 2009 paper published in Ecological Entomology, which forms the empirical basis of the keystone plant concept, the distribution of caterpillar species among host plants is highly skewed: a small number of plant genera support the vast majority of caterpillar species, and most native plant genera support relatively few.

Per Tallamy's data as summarized by Penn State Extension, oaks alone support over 500 caterpillar species in the eastern U.S. Native cherries and plums support over 450. Willows support over 450. By contrast, many popular landscape plants — Japanese maples, Bradford pears, crape myrtles — support fewer than five species each. The implication for home gardeners is significant: a single native oak planted in a suburban yard provides more ecological function per tree than dozens of ornamental non-natives.

I live in zone 7a on Long Island, and the oaks, native viburnums, and serviceberries I've observed in my neighborhood support visibly higher bird and insect diversity than the yards dominated by non-native ornamentals. Whether you're in the Northeast, Southeast, Midwest, Southwest, or Pacific Northwest, the keystone genera — the plants that carry the most food-web weight in your region — differ, and knowing which ones to prioritize is the most efficient approach to restoring ecological function to a managed landscape.

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How to Use This Guide

Plants are organized by region, then by ecological value (number of caterpillar species supported, per the Tallamy lab's data at University of Delaware). For each plant, zones, light requirements, and mature height are from primary sources. "Lepidoptera supported" counts are from Tallamy and Shropshire 2009 and subsequent updates.

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