University of Minnesota

Distinguishing One Milkweed Plant from Another

A milkweed plant, for the purposes of MLMP monitoring, is defined as all above-ground stems originating from a visually-identifiable, common central point in the ground. A single milkweed plant may be composed of one or multiple stems depending on the species. For example, Asclepias viridis (green antelopehorn milkweed) plants often have multiple stems per plant, as do A. tuberosa (butterfly weed) and A. incarnata (swamp milkweed). For these plants, count each cluster of stems originating from the same central point as a single plant. Note that stems from the same plant may be separated by soil. See Figure 1 below.
A single A. syriaca plant may grow many ramets (above-ground as stalks) that are separated by small or large distances. Without excavating roots, it is impossible to tell if ramets are from the same or different plants. Record each individual A. syriaca stalk as one plant.

When we use data gathered by MLMP volunteers in publications, we articulate this methodology so that the findings are not misinterpreted. Consistency in the methodology used is important for MLMP analyses, so we strongly encourage MLMP volunteers to adhere to our “rules of thumb” for observing and recording plants.

If there are uncertainties, please email us for clarification. You can also keep detailed notes about your observations or techniques in the “Notes” section of your site information page.

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