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Botanical and Test Gardens

Monarch Butterfly Habitat & Milkweed Trials Gardens

Monarch butterflies, once common across the United States, have declined by approximately 90 percent over the past two decades. The adult butterflies can obtain nectar from a variety of flowering plants, but the caterpillar stage can only eat milkweeds (Asclepias spp, Funastrum, Gomphocarpus and Tweedia).

In an effort to provide increased butterfly habitat in the Mojave Desert, Master Gardeners have planted 26 different species of milkweed and are documenting their survival, monarch preference and potential for use in the home landscape. Landscape considerations include: evergreen vs. winter dormant, attractiveness of flower, leaf shape and plant size. This research project received the Search for Excellence award at the 2017 International Master Gardener Conference.

Test plots of the various milkweeds are scattered throughout the Demonstration and Test Gardens. Populations are kept separate to prevent hybridization. Master Gardeners collect the milkweed seeds and make them available to the public at the appropriate times for planting. (For instance, for the native Rush Milkweeds we have found that planting in late January ensures the best survival of seedlings and plants.)

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