Monarchs and Milkweed

milkweed monarch map

SVC stewardship staff stumbled upon several displays of showy and narrowleaf milkweed while conducting summer quarterly visits and residual dry matter assessments. Almost all of these sites with milkweed were burned in fires within the past three years. Milkweed is vital for supporting monarch butterflies. Their iconic fall migration is from late summer to November.

Adult monarchs feed on the nectar of many flowers, but they breed only where milkweeds are found. Milkweed serves as the host plant, which means it is the single source of food for the larvae. Without milkweed, the larvae would never be able to become a butterfly. The milkweed also gives the monarch its defense system. It contains a cardiac poison that is harmless to the monarchs, but is poisonous to most invertebrates. The milkweeds’ toxins remain permanently in the monarch’s system, even after the caterpillar metamorphoses into a butterfly.

Monarchs are a very important part of the ecosystem. While feeding on nectar, monarchs pollinate many types of flowers. The flowers they chose are varieties that are brightly colored, grow in clusters, stay open during the day, and have flat surfaces that serve as landing pads for the butterflies. The monarch’s also serve as food for birds, small animals, and other insects.

The Sacramento valley serves a crucial nectar corridor for the migrating butterflies. Nectar corridors are a series of habitat patches containing plants that flower at the appropriate times during the spring and fall migrations. These patches provide stopping-off points for the migrating butterflies to refuel and continue their journey. Having these islands of nectar sources is particularly important within large areas of urban and agricultural development. The discontinuous patches of nectar sources are “corridors” that monarchs will follow, like stepping-stones across a stream to complete their migration.

Threats to monarch habitat:

  • Loss of milkweed plants
    Unfortunately, milkweeds are often eradicated as noxious weeds. Urbanization, industrialized, large-scale farms, and drought conditions have also resulted in significant plant loss.
  • Loss of winter habitat
    The butterflies’ winter habitat in Mexico and California is rapidly shrinking due to deforestation, harsh weather, development and other disruptions. Because all monarchs gather in only a few locations, the overall population is at risk.
  • Climate Change
    Especially during the last decade, changes in climate have resulted in more out-of-season storms, severe temperature drops and excessive rain. The combination of both wet and cold is deadly and has resulted in the deaths of hundreds of millions of butterflies.

Photos by Lisa Couper

Consider maintaining milkweed and plants for native pollinators in your own yard. You can also make a donation today to help protect open space in the Sacramento valley that provides vital habitat for monarchs and other iconic and rare species.

Source info:

Milkweed at Deer Creek Hills Preserve

Stewardship Staff and SVC Docents have identified three species of milkweed on the Preserve. The vast majority is the narrow leaf milkweed. Thank you to Lisa Couper for compiling some additional information about each species and for sharing her gorgeous photos.

    1. Showy milkweed (Asclepias speciosablooms in June/July and at less than 7970 ft. (but may bloom from May to September depending on location specifics) often found in wetlands, riversides and meadows, it will often grow in large patches in these locations. It is a perennial herb with long rhizomatous roots and does not transplant well, but can be grown from sees with the following suggestions from Calscape:

      Propagation – from seed there are two options A. Place the seeds on a bowl with lid in some water or a damp paper towel and place in the fridge for a few weeks or until sprouted. When sprouted place the sprouts flat on their sides into some damp soil. Cover with a very thin layer of soil. These plants should be planted directly into the ground. They don’t transplant well due to long roots (rhizomes) B. Throw seeds onto desired area during the cold months of the year and allow the rain to water them Plant in full sun.
    2. Narrow leaf milkweed also called whorled milkweed (Asclepias fascicularis) it is a perennial herb and it blooms from June through September at elevations to 7875 ft., sometimes riparian or adjacent to rivers and streams, some times dry.Milkweeds in general are the larval host plants for Monarch butterflies, and this species is probably the single most important host plant for Monarch butterflies in California. Milkweed gardeners should be prepared for the plant to be eaten by Monarch caterpillars, but will be rewarded by the presence of beautiful Monarch Butterflies. The plant is deciduous in winter and will sometimes die back to the ground before reviving in the Spring, and is often covered with aphids, so often best to plant in less prominent spots in a garden. It’s very easy to grow in soils with with good drainage, even with no summer water. It can become weedy and if often heavily infested with aphids.

      Propagation: For propagating by seed: No treatment. Seeds need light to germinate so just gently press them into the soil on their sides without burying them. Keep soil moist. Some seeds germinate in as little as 2 weeks after planting, but others in the same bed may continue to germinate for 1-2 months after that.


    3. Purple milkweed aka heart leaf milkweed (Asclepias cordifolia) (do not confuse it with the other ‘purple milkweed’ that is not a California native.)  It blooms from March through July depending on elevation and from 0 to 7480 feet not associated with riparian areas but grows in small clusters to single plants often on dry slopes. Another perennial herb that grows by spreading rhizomes. Native American Miwok utilized this plant for its stems, which they dried and processed into cordage (string and rope). And it can be propagated from seed without special treatment. For Monarchs plant milkweed intermixed with other natives that provide a good nectar source for the adults. These nectar plants do not have to be milkweed.Companion Plants – Works well with a wide variety of other plants, but is best used where its winter leaf loss and summer consumption by caterpillars will not be the center of attention. Also, plant a number of Milkweeds in proximity so that caterpillars will have a sufficient amount to eat. Use with showy, nectar-rich plants that will attract adult Monarchs, such as Indian Mallow (Abutilon palmeri), Ceanothus sp., Western Thistle (Cersium occidentale), California Aster (Corethrogyne filaginifolia), California Fuchsia (Epilobium canum), Buckwheat (Eriogonum sp.), Mint (Monardella sp.), Monkeyflower (Mimulus sp.), Penstemon sp., Sages (Salvia sp.), Apricot Mallow (Sphaeralcea ambigua). – Calscape
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