This plant has a long tuber which creeps underground.  The stem is green and has an upright habit, and can grow 60 to 100 cm in height.  When it becomes mature, its stem color changes into yellowish brown from its base.
The flower forms an umbel, and the long flower stem expands from the axil and 5 to 10 flowers bloom at its tip.  The bud is red and round, and its petals bend backwards and emphasize its yellow corona to show the unique appearance of the family Asclepias.  Its filament of stamen is split into 2, and the outside part becomes a corona and the inside part fuses with the style to form a column.  Inside the corona a corpusculum with 2 polliniums attaches to the column.
After blooming, it bears fruit similar to red peppers.  When ripened, the capsule turns into light brown and tears to release its many seeds with a white silky pappus and release on the wind to fly away.  Thinking about this silky crown, it seemed to be named Foreign Cotton, namely Towata.  Milkweed came to Japan in the Tempo Era (1830 - 1844), during the Edo Era.  During this time everything which came from foreign countries is called To-something even if it was not from China (Wata means cotton, and China was called To).
Milkweed is a toxic plant and contains cardiac glycoside, asclepin (acetylated calotropin), calotropin, etc., in the whole plant.  In China, it is a folk medicine called Renseikeishika that is used as an anti-inflammatory drug, and in South America, it is said that it is used instead of Ipecac, but its toxicity is high so it is risky.
The nectar gland of the Milkweed has a bad smell like feces, so many insects do not approach it, but the Monarch (Danaus plexippus) which is a butterfly native to North America deposits its eggs on this plant.  The hatched larva feeds on the leaf of the Milkweed to grow.  It selectively accumulates the cardiac glycoside and keeps it even after it becomes an imago.  The larva is black with a yellow lattice fringe and stands out, but is almost never targeted by a foreign enemy like a bird or such because birds learn to know that this larva chemically defends itself.
Classification Asclepiadaceae Asclepias
Scientific name Asclepias curassavica LINN.
Japanese name Towata
English name Milkweed
Native locality The West Indies
Ecological description Non-hardy annual---
RDB ---
Planting place Sun Gallery
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