Milkweed Field Trials for Monarch Butterfly Habitat
The Southwest Monarch Butterfly population is in decline. Southern Nevada is part of the Monarch Fall migration from late August to early November. Reproductive Monarchs arrive early as part of the premigration and Milkweeds are their required host plant. The project seeks to identify and cultivate Milkweed species which will survive, flower and attract pollinators in the Mojave Desert. The trials are conducted by the Master Gardeners of Southern Nevada, Monarch Habitat Research Team.
The focus is on gathering sufficient data to determine which Milkweeds are best suited for inclusion in residential landscapes. Another goal is to increase availability of rare native Milkweed seeds through cultivation in the University of Nevada Cooperative Extension Botanical Gardens at 8050 Paradise Road, Las Vegas, NV 89123.
Our target audience is Clark County residents who want to include Milkweeds in their landscape to support the Monarch Butterfly. We are also helping public and non-profit projects by propagating and donating rare native desert-adapted Milkweed seeds. By Fall of 2017, we should be able to share 7 rare species: Asclepias angustifolia, Asclepias erosa, Asclepias fascicularis, Asclepias linaria, Asclepias speciosa, Asclepias subulata and Asclepias texana.
The Mojave Desert is a harsh growing environment:
- 4” average rainfall and 80” evapotranspiration
- Strong dry winds
- Winter temperatures that can dip into the teens
- Summer temperatures in the 120s
- Native soil is alkaline, salty and poor with very low amounts of organic matter.
Six species of Milkweed (Asclepias asperula, A. erosa, A. nyctaginifolia, A. speciosa, A. subulata, A. subverticillata) are native to Clark County. They are not abundant in the wild and are not grown in landscapes. Their seeds are quite rare and difficult to obtain, especially by the general public.
Ease of germination and transplantation varies widely among the Asclepias species.
The best time to germinate seeds appears to be in January for early March planting and in July for early September planting.
Desert-adapted plants can grow deep tap roots very quickly and are sensitive to transplanting. Seedlings do well when germinated indoors and planted ASAP with the second set of adult leaves without disturbing the young tap root.
Each Milkweed in the trials is evaluated:
- Can it survive here?
- Does it need full sun, partial sun or shade?
- Is it dormant or evergreen?
- Is it clumping or does it have rhizomes? How aggressive?
- Is it available to feed Monarch Butterfly caterpillars from late August to late October?
- Are Monarch Butterflies attracted to this Milkweed?
- Is it decorative in a residential garden?
- Can the seed or plant be found?
To help answer these questions, Master Gardeners of Southern Nevada are conducting field trials of 30 different Milkweeds and seven cultivars in the Botanical Gardens of the University of Nevada Cooperative Extension.
As of Spring 2017, we have determined that the Milkweeds best suited for use in a residential garden in Southern Nevada are Asclepias subulata (Rush Milkweed), Asclepias erosa (Desert Milkweed), Asclepias speciosa (Showy Milkweed), Asclepias angustifolia (Arizona Milkweed), Asclepias linaria (Pineneedle Milkweed), Asclepias texana (Texas Milkweed), Asclepias subverticillata (Horsetail Milkweed) and Asclepias curassavica (Tropical Milkweed).