By Charlotte Pitt
Names are often deceiving, and that is certainly the case for the flowering plant commonly known as Milkweed. Plants are considered to be weeds when they are unwanted, but Milkweed is definitely a plant you want to keep around! There are nineteen species of Milkweed native to California, and they are both a beautiful plant that makes an eye-catching addition to any garden and an important habitat and food plant for caterpillars, particularly the caterpillars of the Monarch butterfly. Nine species of Milkweed act as the only food source for the Monarch caterpillars, so these plants are crucial to their survival. Monarch butterflies are at risk of being an endangered species due to a steep decline in population size caused primarily by habitat loss. So, preserving and planting Milkweed is more important now than ever before.
In California the primary species of Monarch butterfly is the Western Monarch, and here in the watersheds of Richmond the Western Monarch eggs and caterpillars can be seen on a species of Milkweed called Narrow Leaf Milkweed. While all Milkweed species are important to Monarch butterflies, Narrow Leaf Milkweed is the most important in California as it is the most abundant and widespread species. Narrow Leaf Milkweed can be identified by its thin, upright stems, its long, narrow leaves, and its clusters of lavender tinted white flowers. Narrow Leaf Milkweed also has long and narrow seed pods that dry out and open, releasing seeds which are covered with light fluffy hairs that allow them to be carried and spread by the wind. Narrow Leaf Milkweed can be found in a variety of habitats, as it can tolerate many different types of soil, as well as low, medium, or high water availability. This also makes Narrow Leaf Milkweed a great choice for both home gardening and restoration, as it can thrive in a variety of conditions.
Another notable species of Milkweed is Showy Milkweed, which can mainly be found in the mountain ranges of Northern California. Showy Milkweed has a narrower range than Narrow Leaf Milkweed as it prefers a more narrow range of conditions, preferring well draining soil and low water availability. Showy Milkweed is also an important species for Monarchs, and is highly valued as a home gardening plant due to its ease of care (in the right conditions), and show-stopping appearance. This Milkweed species has big, beautiful white flowers that are tinged with a pinkish purple color. The leaves of Showy Milkweed are wide and velvety, unlike Narrow Leaf Milkweed, and also add to the beauty of the plant. Showy Milkweed has been a plant long adored and not just for its beauty, as Indigenous peoples use many parts of Showy Milkweed for both food and medicine. Another species of Milkweed utilized by Indigenous people, specifically the Miwok of the San Francisco Bay Area, is Heart Leaf Milkweed. The stems of Heart Leaf Milkweed were dried and made into string and rope, which was used for multiple purposes.
All the species of Milkweed that can be found in California are valuable not only to butterflies and the other insects and birds that are attracted to them, but also to the historical and modern people of California. By protecting the current populations of Milkweed that exist and by planting more Milkweed in both our private homes and in urban and wild landscapes, we would not only be protecting the enjoyment of this versatile plant for generations to come, but also supporting future generations of Monarch butterflies. In support of this goal The Watershed Project is preserving and expanding a small patch of Narrow Leaf Milkweed along the Richmond Greenway, which can be seen near our bioswale by 17th Street.
California Native Plant Society. (n.d.). Heart leaf Milkweed, Asclepias cordifolia. Calscape. https://calscape.org/loc-California/Heart%20Leaf%20Milkweed%20(Asclepias%20cordifolia)?newsearch=1.
California Native Plant Society. (n.d.). Narrow leaf Milkweed, Asclepias fascicularis. Calscape. https://calscape.org/loc-California/Narrow%20Leaf%20Milkweed%20(Asclepias%20fascicularis)?newsearch=1.
California Native Plant Society. (n.d.). Showy milkweed, Asclepias speciosa. Calscape. https://calscape.org/loc-California/Showy%20Milkweed%20(Asclepias%20speciosa)?newsearch=1.
Gayton, V. (2017, May 2). What’s in your watershed: The magnificent monarch butterfly. The Watershed Project. https://thewatershedproject.org/whats-in-your-watershed-the-magnificent-monarch-butterfly/.