25 Mei 2010

Astragalus brauntonii

Astragalus brauntonii is a rare species of milkvetch known by the common name Braunton's milkvetch.

It is endemic to southern California, where it is known from fewer than 20 extant occurrences in the hills and mountains surrounding Los Angeles.

It is a plant of the coastal grassland, scrub, and chaparral plant communities of the area, especially in carbonate soils.

This is a large perennial herb which grows from a woody caudex and reaches up to 1.5 meters tall. The thick hollow stems are coated in coarse white hairs.

Leaves are up to 16 centimeters long and are made up of many pairs of oval-shaped leaflike leaflets. The inflorescence is a dense spike of up to 60 bright lilac flowers. Each pealike flower is about a centimeter long with a reflexed hood.

The flowers wither and turn brown but remain on the plant instead of dropping off. The fruit is a small bent legume pod. This plant, like many chaparral species, is fire-adapted and requires wildfire or other disturbance to propagate.

The beanlike seeds require scarification to break down their tough seed coats before they can germinate. The seeds persist for years in the soil until fire allows them to sprout; populations of the plant spring up in an area that has been recently swept by wildfire.

It is a pioneer species, one of the first to grow in a distubed area and one that is soon crowded out by plant species that appear later in succession.

Fire suppression in the hills around Los Angeles prevent the plant from reproducing.This is a federally listed endangered species in the United States.

Source: http://en.wikipedia.org/wiki/Astragalus_brauntonii

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