Milkweed
To help offset the loss of monarch breeding habitat, the North American Monarch Conservation Plan (published in 2008 by the tri-national Commission for Environmental Cooperation) recommends the planting of regionally appropriate native milkweed species. However, a scarcity of milkweed seed in many regions of the United States has limited opportunities to include the plants in regional restoration efforts.
milkweed
Use the resources to learn more about growing the milkweed species appropriate for planting in your area, find seed suppliers, and discover the many other ways you can contribute to monarch conservation!
Swamp milkweed and butterfly weed are highly ornamental and available in a variety of cultivars. Download this milkweed information sheet from Monarch Joint Venture for regional native recommendations.
The petite, star-shaped flowers of milkweed are perfectly designed for pollination. Depending on the plant, milkweed flowers bloom in yellow, green, purple, pink, or orange. Equally well designed are the large seed pods that develop from the fertilized flowers. In the fall, these proficient self-sowers split open to release hundreds of seeds.
Milkweed is both a food source and a host plant for monarch eggs that are laid on the underside of the leaves. The larvae feed on the leaves after hatching, but cause no permanent damage to the plant. In turn, the toxic chemicals in the sap of milkweed plants make both the caterpillars and adult butterflies unappetizing to predators.
The best soil type for milkweed often depends on its native habitat. Most varieties are extremely forgiving and will grow well in average garden soil. Swamp milkweed is an exception and requires moist, humus-rich soil.
Many milkweed species can readily be grown from root or rhizome cuttings as well as by seed. Take the cuttings during the late fall or early spring when the plant is dormant and has more energy reserves. New sprouts will form from the cuttings when the weather warms and will often produce flowers the first year.
You can mulch milkweed if you want to control weeds or retain moisture, but not all varieties will benefit. Swamp milkweed will appreciate your water-retention efforts, but milkweeds that prefer dry soil, such as common milkweed and butterfly weed, are usually better off with no mulch.
Some plant pests such as aphids, whiteflies and milkweed bugs are immune to the toxic effects of milkweed and may feed on the leaves and seed pods, but they rarely cause significant damage. Also remove leaf litter and spent stalks in the fall to eliminate overwintering sites.
Be aware that the toxic alkaloids in the sap of milkweed that help protect the monarchs from predators can cause eye and skin irritation and are poisonous to pets and other animals when ingested. Take the appropriate precautions and wear gloves, long sleeves, and long pants when working with these plants. See more about Common Poisonous Plants for Dogs & Cats.
This demure beauty is native to prairies and open areas in a large part of central and eastern North America. It is distinguished by narrow rosemary-like leaves, which are arranged in a whorled pattern around the stem, and delicate clusters of white to greenish-white flowers. It also grows well in rocky or clayey soils that are unhospitable to other milkweed species.
Similar in appearance to common milkweed, but less aggressive because it does not spread by rhizomes. Large pale pink to pinkish purple flower clusters up to 3 inches across provide a plentiful nectar source for a variety of butterflies. The leaves are also distinctive, broad and oblong with attractive rose-pink midribs.
Often found growing in dappled sunlight along paths in woodlands and woodland borders, this is one of the few milkweeds suitable for planting in a partially shaded garden. Rather than standing erect, the bicolored green and white flowers droop elegantly over long, pointed leaves.
Successfully establishing milkweed requires some very specific steps. Please refer to our Project Milkweed page for more information on successful milkweed establishment. For those working to Save Western Monarchs by planting milkweed in California, please refer to our fact sheet Native Milkweed in California: Planting and Establishment.
If you are a milkweed vender and would like to either be added to this directory or to make changes to your vendor entry, please submit a vendor interest form for your business, organization, or network.
Monarch caterpillars feed exclusively on the leaves of milkweed, the only host plant for this iconic butterfly species. As such, milkweed is critical for the survival of monarchs. Without it, they cannot complete their life cycle and their populations decline.
The good news is that planting milkweed is one of the easiest ways that each of us can make a difference for monarchs. There are several dozen species of this wildflower native to North America, so no matter where you live, there is at least one milkweed species naturally found in your area.
Planting local milkweed species is always best. You can collect your own seed or purchase seed or plants to add to your garden, or any landscape in your community. Three species have particularly wide ranges and are good choices in most regions: common milkweed (Asclepias syriaca), swamp milkweed (A. incarnata), and butterflyweed (A. tuberosa). The latter two are highly ornamental and widely available via the nursery trade.
Note: Tropical milkweed available at many retail nurseries is not native to the U.S. However it has naturalized in the Southeastern U.S. Science is discovering that its long bloom time may have some detrimental effects on monarch migration and possibly be a source to spread disease within monarch populations. If you do have tropical milkweed in your garden, it is recommended to cut the plant back in the winter months to encourage monarchs to move on to their natural overwintering sites.
Monarch larvae appear to feed exclusively on milkweeds (Asclepidacae). This family name is derived from Asklepios, the Greek god of medicine and healing. Most members of the genus Asclepias are tropical; however, there are more than 100 species of Asclepias and several genera of viny milkweeds in North America and monarch larvae have been observed feeding on many of these. Milkweeds are perennial plants, which means an individual plant lives for more than one year, growing each spring from rootstock and seeds rather than seeds alone. In the Midwest, milkweeds were historically common and widespread on prairies, but habitat destruction has reduced their range and numbers.
The name "milkweed" refers to the milky latex contained within the leaves. Most species are toxic to vertebrate herbivores if ingested due to the cardenolide alkaloids contained in the leaves and stems. When monarch larvae ingest milkweed, they also ingest the plants' toxins, called cardiac glycosides. They sequester these compounds in their exoskeletons, making the larvae and adults toxic to many potential predators. Vertebrate predators may avoid monarchs because they learn that the larvae and adults taste bad and/or make them vomit. There is considerable variation in the amount of toxins in different species of plants. Some northern species of milkweed contain almost no toxins while others seem to contain so much of the toxins that they are even lethal to monarch caterpillars.
Like other flowers, milkweeds have floral whorls of sepals (collectively referred to as the calyx) and petals (collectively called the corolla). Flowers of milkweeds are interesting because they have an third whorl of five hoods each of which encloses a horn (modified filaments of the anthers). Together, hoods and horns are referred to as the corona. The horns of some species are long, while the horns of others are reduced to the point they cannot be seen.
5th instar Monarch larvae are voracious and quickly consume entire leaves. In order to minimize the flow of the milkweed's sap, they will sometimes chew a notch in the leaf's petiole, causing the leaf to hang down. This behavior is known as flagging.
Aphids - These tiny yellow insects are often found in large numbers on milkweeds. They tap into the plant and feed on its juices, so feeding damage is not obvious; however, they are a useful indicator of milkweed, especially when differentiating Blue Vine milkweed from Bind weed.
Milkweeds can be propagated from seeds, cuttings, and, in some cases, from root divisions. This account will deal with storage, treatment and planting of milkweeds seeds and will briefly touch on propagation from cuttings.
Milkweed seeds can be planted in prepared beds outdoors or started indoors in flats. We recommend the latter approach since germination rates are generally higher indoors and it is easier to establish your milkweeds with transplanted seedlings that are well-rooted and therefore more resistant to weather extremes and pests.
Milkweed seeds can be sown outdoors after the danger of frost has passed. Refer to the seed packets for special instructions on sowing the seeds. Keep in mind that seeds have a range of soil temperatures at which they will germinate. Also, remember that under sunny conditions the soil temperatures can be much higher in the daytime than the ambient air temperatures you experience. Plant the seeds early since those planted late in the season may not germinate because of high temperatures. In addition, new seedlings from late plantings can "dry off" before they are even noticed. Asclepias incarnata (swamp milkweed) and A. syriaca (common milkweed) germinate poorly at high temperatures (>85F). However, other species such as A. curassavica (tropical milkweed) and Cynanchum laeve (blue vine) germinate well at these temperatures. Germination outdoors depends on soil moisture and temperature and could take several weeks if conditions are not ideal.
All milkweeds are perennials and some can be grown from cuttings. Cuttings provide a way producing new plants in a relatively short time and it avoids some of the difficulties of starting plants from seeds. To start cuttings, cut the stems underwater, then coat the bottom of the stem with a strong rooting hormone. The stems should be placed in sand, vermiculite, or potting soil that is kept continuously moist. Cuttings can usually be transplanted in 6-10 weeks. Survival is best when cuttings are made from green stems (1/3 inch diameter) obtained from plants fertilized two weeks earlier. 041b061a72