A collection of flora from the pacific wonderland.

Narrow-Leaved Milkweed (Asclepias fascicularis)

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Rowena Plateau, Tom McCall Preserve, Columbia Gorge, OR, 7/2015

Milkweeds, genus Asclepias, are often plain, overlooked, and rarely appear in our wildflower reference guides, but A. fascicularis, in particular is critical to the survival of  Monarch butterflies!

Surprisingly, Milkweed flowers rival Orchids in complexity. Their petals reflex backwards, stamens and styles are fused, and they have a unique paired hood and horn structure where they pollen is hidden in sacks tucked between the hoods.  When pollinating, insects rub their back on the pollen. The size, shape and color of the horns and hoods are identifying characteristics. A distinguishing characteristic of the Narrow-Leaved Milkweed, as it name implies, is its long, pointed, very narrow leaves.  After the bloom, milkweed fruit pods break open to reveal seeds born on ‘silks’ or ‘floss’ that scatter in the wind.  In fact, Milkweed ‘floss’ is highly insulating and even grown commercially for pillow filling and winter coat insulation!

Milkweeds are an important nectar source for bees and wasps, and a key larvae food for Monarch butterflies, who lay their eggs on the underside of the leaves.  To survive the damage from hungry larvae (which can consume up to one leaf a day!) milkweeds have evolved to grow faster than they are eaten, and exude a toxic latex when cells are damaged.  Monarch larvae, in turn, evolved to avoid the poison by eating in a circular pattern.  Still, fewer than one in 10 Monarch eggs and caterpillars survive to maturity.  Environmental degradation has dampened the Milkweed population, and this may have contributed to the recent decline in Monarch butterflies.

Native tribes used the toxic ‘milk’ from the Milkweed plant on their arrowheads to aid in hunting.

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Rowena Plateau, Tom McCall Preserve, Columbia Gorge, OR, 7/2015

 

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