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Helpline Hot Topic for November 

Milkweed for Monarchs – What You Should Know

By Cynthia Zimmerman

“Well, I must endure the presence of a few caterpillars if I wish to become acquainted with the butterflies.”- Antoine de Saint-Exupe´ry, The Little Prince

Monarch butterflies are more than beautiful; they contribute to the health of our planet by feeding on nectar and pollinating many types of wildflowers. They are also part of nature’s food chain as an important source of food for birds, small animals, and other insects. Considered an ‘indicator species,’ which basically means it is the canary in the mine, they are quite sensitive to climate change, harmful chemicals in the environment, and the removal of natural habitats due to development, land clearing, large farm practices, and increased use of herbicides.

Due to the decline of Monarch butterflies and their shrinking migratory paths in the United States, home gardeners are being encouraged to plant milkweed. Why milkweed? Monarchs cannot survive without milkweed. The females only lay their eggs on milkweed as they migrate. In order to grow and develop their caterpillars need milkweed plants.

Before you run to the nearest garden shop, nursery, or box store garden center in order to help the plight of the Monarch, there is something you should consider. There are many, many milkweeds on the market, some native and some tropical. Monarch Joint Venture, Xerces Society and the U.S. Fish and Wildlife Service, all of which are dedicated to saving the Monarch, all recommend only planting milkweed varieties that are native to your location.

Native milkweed in California typically flowers between late spring and the end of summer. Following seed dispersal, the aboveground portion of the plant dies back to the ground remaining dormant through the winter. In spring it re-emerges from the established root system.

Many of the varieties being sold are tropical milkweeds which are not native to the U.S. and have foliage year-round when it grows where winters are mild and adequate moisture is available (in this circumstance Fresno is considered mild). Research suggests that the tropical milkweed may encourage monarchs to lay eggs outside of their regular breeding season, disrupting their migratory cycle, and increasing the prevalence of monarch infection by the protozoan parasite Ophryocystis elektroscirrha, aka “OE”. If you have already planted a tropical milkweed in your garden, it is suggested that you cut it to the ground in fall when natives would be dying back. It should re-emerge in the spring. This would eliminate the female from laying eggs at the wrong time in their migration.

The following California species should be your first choices when planting milkweed in Fresno, Clovis and surrounding areas

1. Butterflyweed (Asclepias tuberosa) – sometimes called Orange Milkweed. Large flat-topped clusters of yellow-orange or bright-orange flowers. Blooms May to September. Needs sunlight. Drought tolerant, dry or moist soil. 1-2 ft. tall.

2. Antelope-horns Milkweed (Asclepias asperula) – Also known as Spider Milkweed. Pale greenish-yellow flowers, tinged with maroon. Blooms March to October. Needs sunlight, dry or moist soil. Medium water use. 1-2 ft. tall.

3. Showy Milkweed (Asclepias speciosa) – Blooms May to September. Blue-green leaves and spherical clusters of rose-colored flowers. Shade tolerant, needs some sunlight. Medium water use. Moist soil. 1 1⁄2-3 ft. tall but can reach 6 ft. under favorable conditions.

4. California Milkweed (Asclepias californica) – Native to Central and Southern California. White-wooly plant and deep purple flowers. Blooms May to July. Drought tolerant, dry slopes. Maximum height 3 ft.

5. Mexican Whorled Milkweed (Asclepias fascicularis) – aka Narrowleaf milkweed. Clusters of greenish-white flowers often tinged with purple. Blooms June to September. Needs sunlight. Drought tolerant. Dry to moist soil. 1-2 1⁄2 ft. tall.

6. Desert Milkweed (Asclepias erosa) – White to yellow flowers. Green to yellow stems. Blooms April to October. Best grown in desert conditions of sandy soil. Needs sunlight, dry soils. Not shade tolerant. 1-3 ft. tall.

Although milkweed does contain toxins, it is not usually a significant threat to animals or humans. Milkweed has a foul taste and is not likely to be consumed by pets or children in a quantity that would prove harmful. Still it is best to prevent accidental ingestion by teaching children to avoid contact with the plant and to wash their hands if they do touch it. If animal or human poisoning is suspected, call the poison control center or seek medical help.

For more information on Milkweed and Monarchs go to the following websites:

https://www.nwf.org/Garden-For-Wildlife/About/Native-Plants/Milkweed.aspx

Milkweed for Monarchs

https://www.growmilkweedplants.com/map.html

Native Milkweed by State

http://xerces.org/milkweed-faq/

Milkweed FAQ

https://monarchjointventure.org/images/uploads/documents/MilkweedFactSheetFINAL.pdf

Monarch joint venture chart

https://journeynorth.org/monarchs

Journey North Tracking Migrations

https://www.nps.gov/articles/monarch-butterfly.htm

Pollinators – Monarch Butterfly