Sunday, June 19, 2011

Clasping Milkweed (Asclepias amplexicaulis): Shoots, Leaves And Flower Buds

During Winter visits to the Broad River Wildlife Management Area (WMA) in Wilkes County, Georgia, we’d see the dried horn-shaped seedpods of an Asclepias species. Although we weren’t sure which species it was, based on remnants of leaves on a few plants, we suspected it was Asclepias amplexicaulis, the Clasping Milkweed. This year we decided to put some effort into identifying this species and photograph it from its emergence in the Spring through its development of buds, flowers, and seedpods until it released seeds. We’ve been following plants in Wildlife Management Areas in Wilkes, Greene, Hancock, and Jasper counties.

Asclepias amplexicaulis
is known by the common names Clasping Milkweed, Blunt-leaved Milkweed, Blunt-leaf Milkweed, or Sand milkweed. Asclepias sp. are perennial and are among the last perennials to emerge in the Spring. Plants may grow from seed or from rhizomes in a single stalk as high as 3-4 feet tall. Flowers form in a terminal umbel.

We’ve found plants in well-draining soil and often at the edges of pine forests but infrequently in deciduous
woods. Plants seem to grow best in partial shade although we’ve found some plants growing in full sun.

Plants produces a poisonous milky sap. Monarch (Danaus plexippus) butterflies lay eggs on leaves of Asclepias sp.; caterpillars eat the leaves, absorb the toxins and become unattractive to predators.

A newly emerged sprout. The lower leaves are cotyledons. The true leaves develop next. This plant has a couple of sets of young true leaves and is already starting to set flower buds.

True leaves are sessile, and opposite in this species. Young leaves are elliptical.

When true leaves mature, they are oblong in shape, clasp around the stem at the base, and have a wavy edge. These characteristic leaves make them relatively easy to spot from a distance and give them one of their common names – Blunt-leaved Milkweed.

Flower buds are just starting to develop

From a different angle

Small buds just starting to show the 5-part shape that is characteristic of Asclepias sp.

A little bigger, from above…

And from the side

Almost ready to bloom

Spotting an Asclepias amplexicaulis plant developing blooms

Asclepias amplexicaulis
is native to the United States and found states east of a line from Minnesota south to Louisiana and states west of this line including Nebraska, Kansas, Oklahoma and Texas.

Next: The flowers...

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- United States Department of Agriculture Plants Database:
Asclepias amplexicaulis (Clasping milkweed)
- University of North Carolina Herbarium: Asclepias amplexicaulis

Identification resources:

- Southeastern Flora: Clasping milkweed (Asclepias amplexicaulis)

- Missouri Plants: Asclepias amplexicaulis

- Kansas Wildflowers and Grasses: Blunt-leaf Milkweed

- Natural and Naturalized Plants of the Carolinas and Georgia:
Asclepias amplexicaulis (Clasping milkweed, Blunt-leaved Milkweed)

Related posts:

- 2010: Year Of The Wildflower – Wildflower Index

- Green Comet Milkweed (Asclepias viridiflora)

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