A Role for Native Weeds

A Role for Native Weeds and Aggressive Plants for Replacing (or Competing with) Invasives in Badly Degraded Areas

Written by:  James Reinartz, UW-Milwaukee Field Station, Saukville, WI (author for correspondence Email); Marc White, Riveredge Nature Center, Newburg, WI; Jill Hapner, Washington County Department of Planning and Parks, West Bend, WI

Planting of desirable vegetation is often suggested as a follow-up to invasive plant control, removal, or eradication. Invasive species often re-colonize the newly-created open habitat following management, and native plant propagules are frequently not present. Furthermore, many of the later-successional native species that may be characteristic of the restoration target community are poor competitors with the invasives that we seek to replace. It seems that initial replacement of, or competition with, invasives should be a role for the most aggressive native plants in our flora, however, there are few lists of tough or aggressive native species, especially native weeds, that may be equal to the task of competing with displacing the invasives.

We are of the opinion that in general even our most aggressive and weedy native species are preferable to invasive plants, and in most cases preferable to any non-native species, to establish in areas where the goal is managing natural vegetation. Early successional (weedy) native species are probably underutilized as cover or “nurse” crops and for establishment of an initial plant community on areas where a severe infestation of invasives has been removed.

There is an important role for native weeds. These early-successional species were present in naturally disturbed areas before European settlement and subsequent widespread landscape disturbance. Native weeds may make very good cover crops for plantings of more conservative native species, but little research has been conducted on the efficacy of native weeds as cover. We realize that our opinion may not be widely shared, but we see potential roles for such species as gray dogwood, prickly ash, common cocklebur, and perhaps even Canada goldenrod in the early stages of native plant community restoration.

We offer here a list of weedy and potentially aggressive species that are native and widespread in Wisconsin. We know that this list is not complete. There are undoubtedly additional, more “conservative”, species not included on this list that are nonetheless very good competitors with non-natives; and there are surely some species on this list that are poor competitors or colonizers despite their very low Coefficient of Conservatism. Most managers of natural areas have noticed weedy or aggressive natives that hold their own in competition with non-native species. Our hope is that the reader will contact us with information about additional species or observations about the species on this list so that we can compile and present a more comprehensive list of the Wisconsin natives best able to compete with our invasive plant problems.

Weedy and Aggressive Plant Species Native to Wisconsin was formed by selecting native plant species from the University of Wisconsin; Stevens Point, Robert W. Freckmann Herbarium. We chose species that, 1) have been assigned a low Coefficient of Conservatism (C), 2) are relatively widespread in Wisconsin, and 3) in the experience of the authors seem to be able to hold their in competition with non-native species. The Coefficient of Conservatism is a number on a scale from 0 to 10 that represents an estimated probability that a plant species is likely to occur only in a landscape relatively unaltered from what is believed to be a pre-settlement condition. A low C represents a high tolerance for disturbance and a low fidelity to any particular pre-settlement plant community type exceptperhaps disturbed areas.

Weedy and Aggressive Plant Species Native to Wisconsin is a DRAFT! Please contribute your experience to this effort to help us all learn more about our native weeds.

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