Ann Wright: Magnificent monarchs rely on native plants
July 27, 2018
As metamorphosis is completed, a monarch butterfly with colorful orange, black and white wings emerges from a green egg-shaped chrysalis, once a yellow and black-striped caterpillar chewing mightily on leaves of milkweed plants.
With news of the decline in migratory monarch butterfly populations, milkweed (Asclepias spp.) has become a much sought-after plant for back yard gardeners and citizens interested in the fascinating world of the monarch butterfly.
As the required host plant for the monarch butterfly, milkweed is essential to monarch survival. Monarchs lay their eggs on milkweed and the plant plays an important part in protection from predators as the milkweed contains compounds that create toxins distasteful to predators.
Once the egg has been laid on the milkweed plant, usually on the bottom of a leaf, the egg will hatch in about four days. Life begins as the larva (caterpillar) eats the egg shell after which they move on to eating the leaves of the milkweed. It is during this stage (10 to 14 days) that the caterpillar grows the most.
Preserving the butterfly beauties
The loss of milkweed due to agriculture and urban development, and destruction by herbicidal spraying is a significant factor in the decline of monarch populations. Restoration of native milkweed habitats and protection of existing milkweed areas is a huge step in reversing the trend in butterfly loss.
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Additionally, the availability of high-quality nectar which milkweed produces supports many beneficial insects that are naturally predatory and may help control garden and crop pests. Studies have shown that showy milkweed (Asclepias speciosa) attracts a high number of beneficial insects, including ladybeetles and mature pirate bugs.
Although there are about 15 types of milkweed native to California, the following four species are native to our area and are recommended for restoration or creating habitat for monarchs:
Asclepias speciosa, commonly called showy milkweed
A. fasicularis, also known as narrow leaf milkweed
A. eriocarpa, also called wooly pod or Indian milkweed
A. cordifolia, known as purple or heartleaf milkweed
It is important to remember that when a species of plant or animal develops in a given area over time, that species tends to thrive when grown in its native habitat. In this case, the native milkweed is what the Western monarchs "expect to find" in this area and are the best ones to benefit the health of the transient monarchs.
Non-native milkweed species that don't die back can encourage monarchs to stay in the area, trying to breed, instead of migrating to the coast. This will endanger both adults and late hatching larvae from death by winter freezes in the area. Also, late growing milkweed presents a higher danger of the presence of monarch protozoan parasites which can weaken or kill both adults and larvae.
In addition to milkweed, adult monarchs require diverse sources of nectar at all times of the year to optimize health during spring and summer breeding, for migration and overwintering. Native plants such as desert willow, sunflowers, sulfur-flower buckwheat and many others help sustain the monarchs.
To learn more about these fascinating creatures and how to help sustain them in our area, join the Nevada County Master Gardeners at a free workshop, "Monarch Butterflies and Milkweed in Your Garden," from 10 a.m. to noon Saturday, Aug. 4, at the Demonstration garden on the Nevada Irrigation District grounds, 1036 West Main St. in Grass Valley.
In addition to identifying monarchs at various stages of development, topics will include: the greatest dangers to the Monarch population; why milkweed is important to the survival of the Monarchs; and which milkweed plants are best suited to our foothill climate.
For more information on this or other Master Gardener events, call 530-273-0919 or go to the website at http://www.ncmg.ucanr.org.
The Xerces Society is a great source for more information on monarchs and other pollinators. The website is (https://xerces.org/monarchs/).
Ann Wright is a Nevada County Master Gardener.