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Sunday, June 9, 2013

A Multitude of Milkweeds

Swamp Milkweed, Asclepias incarnata
Butterfly Milkweed, Asclepias tuberosa
Plants known as milkweeds belong to the genus Asclepias, named after the Greek god of healing, and those known as milkvines belong to the genus Matelea, but both are part of the Dogbane family. Over 40 species of milkweeds and milkvines are native to Texas, and those most notable that are blooming this time of year in Central Texas include Antelopehorns (Asclepias asperula), Texas Milkweed (Asclepias texana), Purple Milkvine (Matelea biflora), and Pearl Milkvine (Matelea reticulata). 

Milkweeds and milkvines are named for their milky juice, which contains alkaloids, latex, and other complex compounds, and some species are known to be toxic. Despite this toxicity, the sap of these plants has been used in many folk remedies, including clotting of small wounds, removal of warts, and as a natural treatment for the undesirable effects of poison ivy. These plants are also an important nectar source for bees and other insects, and are a larval food source for Monarch butterflies and their relatives.

Antelopehorns, Asclepias asperula
Texas Milkweed, Asclepias texana
Forming low clumps 1 to 2 feet across in grassy meadows, Antelopehorns is mostly recognizable by the solitary, rounded arrangement of numerous pale yellowish green flowers at the end of each stem, appearing from March through May.  The leaves are slender and 2 to 6 inches long, often folded lengthwise along the midrib.  Texas Milkweed is a much more upright plant, reaching 6 to 18 inches high, and found on limestone outcrops, hillsides, and in dry fields. Its herbaceous leaves are elliptical and each cluster of white flowers is solitary and forms at the top of branched stems from May to July.  Both of these Asclepias species produce seeds in pod-shaped follicles.  These seeds are arranged in overlapping rows, and have silky filament-like hairs called ‘pappus’ attached to them.  Once the follicles ripen and dry out, they split open and the seeds are carried off by their silken hairs and dispersed by the wind.  

Pearl Milkvine, Matelea reticulata
Plateau Milkvine, Matelea edwardsensis
Usually found in the chalky soils of pastures and open ground, Purple Milkvine is often overlooked and missed.  Its low-growing 2 foot stems radiate from a woody rootstock, and along with its opposite, triangular leaves, are covered with long, spreading hairs.  From April to June, pairs of star-shaped, five-petaled, dark purple flowers rise from the base of the leaves.  A robust, twining vine growing in dry, light shade in thickets on rocky hillsides, Pearl Milkvine is best known for its heart-shaped leaves and flat, green flowers ½ to ¾ of an inch across with pearly, iridescent centers.   These curious flowers have tiny white veins forming an intricate pattern on the surface of the petals, adding to their unusual look.

Milkweeds are a versatile group of plants and are now found in many butterfly gardens.  Studies have shown them to re-grow faster than caterpillars can consume them, allowing the overall plant to continue to survive.  The silk or floss from their follicles have good insulation qualities, even superior to down feathers, and they are now grown commercially as a hypoallergenic filling for pillows.  Even Native Americans have used the nectar from the plant as a source of sweetener, due to its high dextrose content. So, as you can see, there are multiple milkweeds with a multitude of uses!