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Multiple Milkweed Species

What if I have more than one species of milkweed? Do I have to monitor all of them?

You are not required to monitor all of the milkweed species at your MLMP site. Some milkweed species are more difficult to monitor than others, so you may choose not to monitor certain species if they are particularly difficult or time-consuming to observe. If you do choose to monitor multiple species at the same site, we recommend using Datasheet 1C for Measuring Monarch Density, which allows you to track monarch activity for each species separately. Remember to be consistent from week to week. In other words, don’t start monitoring Asclepias tuberosa (butterfly weed) mid-season if you have excluded it from your weekly monitoring earlier in the season. You should, however, include ALL milkweed species that are present at your site in the Site Description form, even if you are not monitoring them.

When using Datasheet 1C, remember to use a different table for each species of milkweed. The datasheet has two tables on it already, so if you monitor more than two species you will use additional datasheets (or develop your own datasheet for collecting information - just make sure you are recording all of the data fields we are asking for!). Remember to indicate which table corresponds to which species.


Your site has 3 species of milkweed – common milkweed, swamp milkweed, and butterfly weed. You choose to only monitor the common and swamp milkweed because there are too many stems on butterfly weed and you find it both time consuming to observe and it is difficult for you to find the eggs or caterpillars on that plant. Since you are excluding butterfly weed from your weekly monitoring activities, you record observations on Datasheet 1C using both tables – one for common milkweed and the other for swamp milkweed. If using Datasheet 1A, you do not have to distinguish one milkweed species from another when recording data - simply treat the different species you observe equally and record your findings on the table on Datasheet 1A. List each of the three species of milkweed that are present at your site (common milkweed, swamp milkweed, and butterfly weed) on your Site Description form that you update each season, even though you are not monitoring all of them.

Sub-sampling Consideration

If you are monitoring multiple species of milkweed at a single site using a sub-sampling method because there are too many milkweed plants at your site to monitor them all, you do not need to do multiple transects per species. Let’s say your site has both common milkweed and swamp milkweed. Using the transect method, you would monitor each milkweed (both common and swamp) you see along your straight-line transect by recording it in the appropriate table on your datasheet (if using Datasheet 1C). If you are monitoring using the systematic method, you would treat both species the same, only observing one for every x number that you’ve chosen to monitor. BUT, remember to record different species in the appropriate table on your datasheet if using Datasheet 1C (use a separate table for each species).

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