Milkweed is named for its milky sap, which consists of a latex containing alkaloids and several other complex compounds including cardenolides.  Some species are known to be toxic.

Carl Linnaeus named the genus after Asclepius, the Greek god of healing, because of the many folk-medicinal uses for the milkweed plants.

Pollination in this genus is accomplished in an unusual manner. Pollen is grouped into complex structures called pollinia (or “pollen sacs”), rather than being individual grains or tetrads, as is typical for most plants. The feet or mouthparts of flower-visiting insects such as bees, wasps and butterflies, slip into one of the five slits in each flower formed by adjacent anthers. The bases of the pollinia then mechanically attach to the insect, pulling a pair of pollen sacs free when the pollinator flies off, assuming the insect is large enough to produce the necessary pulling force (if not, the insect may become trapped and die. Pollination is effected by the reverse procedure in which one of the pollinia becomes trapped within the anther slit.

Asclepias species produce their seeds in follicles. The seeds, which are arranged in overlapping rows, bear a cluster white, silky, filament-like hairs known as the coma[4] (often referred to by other names such as pappus, “floss”, “plume”, or “silk”). The follicles ripen and split open, and the seeds, each carried by its coma, are blown by the wind.

They have many different flower colorations, depending on species.

http://en.wikipedia.org/wiki/Asclepias

Help Monarchs with the Right Milkweeds

Milkweeds Native to your Region

The most important thing you can do is to plant the milkweeds that are the most common in your own region, and here is a way to find out what those are. The following link is from the Monarchwatch.org site, where you will find each state listed with all the milkweeds that grow there named.

http://nativeplantwildlifegarden.com/help-monarchs-with-the-right-milkweeds/

Milkweed Seed Finder

Native milkweeds (Asclepias spp.) are essential for monarch butterfly (Danaus plexippus) caterpillars and support a diversity of pollinators with their abundant nectar. By including milkweeds in gardens, landscaping, wildlife habitat restoration projects, and native revegetation efforts you can provide breeding habitat for monarchs and a valuable nectar source for butterflies, bees, and other beneficial insects. As part of our Project Milkweed, we have created this comprehensive national directory of milkweed seed vendors to help you find sources of seed. To learn more about monarch butterflies and how you can participate in conservation efforts, please visit the Xerces Society’s Monarch Butterfly and Western Monarch Conservation Campaign pages or the Monarch Joint Venture webpage. 

Please use the drop-down menus below to search for seed sources by species and/or state. Below the search function, you can read more about finding and selecting the milkweed seed that is right for your area.

Before using the Seed Finder, please note that:

• Milkweed seed is currently unavailable in several areas of the country. If you do not receive any results when you search by state, we have not learned of any milkweed vendors located there. Please search other states in your region for vendors who may carry local ecotype seed that is appropriate for planting in your area.
• A seed vendor’s physical address does not always reflect the origin of the seed that they carry. Please always ask vendors for information about seed origin and whenever possible, try to plant seed that is as locally sourced as possible.
• Some of the vendors listed are wholesale only and require a minimum order amount.
• In most parts of the country, it is best to plant milkweed seed in the fall; however spring planting is possible in some areas. Please ask your regional seed vendor for planting recommendations.

Search For Native Milkweed Seed~ 

http://www.xerces.org/milkweed-seed-finder/

GROWING MILKWEEDS

Introduction
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.

http://www.ourhabitatgarden.org/creatures/milkweed-growing.html

Germinating, Growing and Transplanting
Milkweed seedlings can be started indoors in a greenhouse or under artificial lighting and then transplanted outdoors after the average date of last frost. If seeds are started indoors, allow 4-8 weeks growing time before transplanting. Plastic flats can be used to start the seeds. Fill the flats with a soil mix suitable for seedlings (most potting mixes are), thoroughly soak the soil, and let the excess water drain. Sow the seeds by scattering them on the soil surface 1/4-1/2 inch apart, and then cover with about 1/4 inch of additional soil mix. Gently mist the soil surface with water to dampen the additional soil mix that has been added. In an effort to improve germination rates, many gardeners place the seeds in packets made from paper towels and soak them in warm water for 24 hours prior to planting. This method seems to work especially well for seeds of species that require vernalization (see below).

Read in Full Here :

http://www.monarchwatch.org/milkweed/prop.htm

Common Milkweed ~ Asclepias syriaca

Milkweed family (Asclepiadaceae)

Cultivation: The preference is full sun, rich loamy soil, and mesic conditions, but this robust plant can tolerate a variety of situations, including partial sun and a high clay or sand content in the soil. Under ideal conditions, Common Milkweed can become 6′ tall and spread aggressively, but it is more typically about 3-4′ tall. This plant is very easy to grow once it becomes established.

Range & Habitat: Habitats include moist to dry black soil prairies, sand prairies, sand dunes along lake shores, thickets, woodland borders, fields and pastures, abandoned fields, vacant lots, fence rows, and areas along railroads and roadsides. This plant is a colonizer of disturbed areas in both natural and developed habitats.

http://www.illinoiswildflowers.info/weeds/plants/cm_milkweed.htm

Deadline March 2: Ask the Fish & Wildlife Service to Put the Monarch Butterfly on the Endangered Species List – See more at:

http://salsa3.salsalabs.com/o/50865/p/dia/action3/common/public/?action_KEY=15690

Flight of the Butterflies 3D

The monarch butterfly is a true marvel of nature. Weighing less than a penny, it makes one of the longest migrations on Earth across a continent to a place it has never known. Follow the monarchs’ perilous journey and experience millions of them in the remote mountain peaks of Mexico, with breathtaking cinematography from an award winning team including Oscar® winner Peter Parks. Be captivated by the true and compelling story of an intrepid scientist’s 40-year search to find their secret hideaway. Unravel the mysteries and experience the Flight of the Butterflies.
http://www.si.edu/Imax/movie/71