Thursday, September 17, 2015

The Pea Family

Beach pea flowers, Lathyrus japonicus
If you've grown sweet peas or garden peas, you'll instantly recognize their relative growing on the shoreline. Beach peas share the Leguminosae * family resemblance in clusters of flowers and 'bean' pods.
Beach pea pods at Halibut Point tide line
Beach peas clamber over anything their tendrils can grasp, in a modest way. Its ambitious cousin wisteria aims to entwine acres of trees.
Wisteria pods high in a tree
Wisteria japonica flowers
Wisteria's foliage, flowers and fruit are visibly pea-like.

Black locust in bloom, Robinia pseudo-acacia
Black locusts extend the diversity of the legume family to include tall woody trees on Halibut Point.

It could be said that botanical evolution culminates in the dicotyledons that contain our most familiar flowering plants. Among the distinctions that give them a different 'look' from monocots are the pair (versus single) of embryonic leaves, the netted (versus parallel) vein pattern in the leaves, and the flower parts in fours or fives (versus threes). Contrast the pea family with grasses and lilies as charted above.

Legumes have always been nutritionally important to mankind. The pea family includes beans, soybeans, chickpeas, alfalfa and peanuts.
American groundnut, Apios americana
Groundnuts (wild beans or Indian potatoes) produce tubers that were a staple food for Native Americans, and an important factor in the survival of the Pilgrims during the first few winters of their settlement. Pound for pound they contain three times the protein of potatoes, ten times the calcium, and twice the iron. **

As a member of the legume family the groundnut's ability to supply its own nitrogen in partnership with  soil bacteria could be a great advantage in comparison to root crops that require extensive fertilization. But because it has not yet been coaxed into yielding significantly enough in a single season it has not been assimilated into modern agriculture.
Red and white clover, Trifolium pratense and T. repens

Palmate hop clover, Trifolium aureum
Also found at Halibut Point are two other species of the genus Trifolium, Lesser hop clover (T. dubium) and Pinnate hop clover (T. campestre); as well as members of the genus Meliolotus, white-sweet-clover (M. albus) and yellow-sweet-clover (M. officinalis).

Various clovers have been extensively cultivated as livestock fodder plants, either sown alone or in a mixture with ryegrass to form a staple crop for silaging. They are also welcome in pastures and meadows as a nectar source by beekeepers.
Rabbit-foot clover, Trifolium arvense
While not a forage crop, the nitrogen-fixing properties of rabbit-foot clover enable it to prosper in lean soil locations.
Cow vetch, Vicia cracca
Vetches have made similar contributions to both natural and agricultural ecologies as clovers, enriching soil, planted as green manure in crop rotation plans, favored as livestock feed.

Like many legumes they host rhizobia bacteria within structures called root nodules. These bacteria have the ability to convert nitrogen gas  from the air into a form that is usable to the plant. Nitrogen fixation results from a classic symbiotic relationship beneficial to both organisms.
Four-seeded vetch, Vicia tetrasperma

Crown-vetch, Securigera varia

Bird's-foot-trefoil, Lotus corniculatus

Bird's-foot-trefoil, with many of the same utilitarian qualities as vetch, presents a startlingly beautiful wildflower in impoverished soils. A double-flowered variety has been introduced to horticulture.

Blue lupine, Lupinus polyphyllus
Last year, when a presently lawn area in the State Park grew luxuriantly as a meadow, lupines bloomed in profusion.

Lupine seeds are large and edible enough to have been used as a food for over 3000 years around the Mediterranean and for as much as 6000 years in the Andean highlands.
The legume family is unrivaled in its combined ornamental and comestible value to mankind.
* Most authorities use the name Fabaceae (from Latin faba for 'bean') for the pea family. I prefer to retain Leguminosae, an older name still considered valid, for its reference to the fruit of these plants, which are called legumes.
** I derived much of the information in this essay from pertinent Wikipedia articles

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