White Sweet Clover: White Dainty Flowers of Fragrant Melilotus albus

Summary: White Sweet Clover (Melilotus albus) is an Old World biennial wildflower native to Eurasia, extensively naturalized, especially in Canada and the Americas.

Holly Blue Butterfly (Celastrina argiolus) nectaring on White Sweet Clover (Melilotus albus), Weinsberg, Baden-Württemberg state, southwestern Germany: Rosenzweig, CC BY SA 3.0, via Wikimedia Commons

Melilotus albus is an Old World biennial (Latin: biennium, “two-year period”; from bis, “twice” + annus, “year”) wildflower native to Eurasia. The congenial wildflower, with unfussy habitat preferences, claims native homelands from Central Europe eastward to Siberia and China.

Melilotus albus has expanded its range beyond native homelands via successful introductions, especially in North America. Melilotus albus, along with its relative Melilotus officinalis (Yellow Sweet Clover), has thrived in the United States since 17th century introduction especially in agriculture for cattle forage. Melilotus albus is similarly widespread across Canada.

Particular attributes facilitated commercial popularization of Melilotus officinalis in Canada and the United States. The medicinal anticlotting property of dicoumarol, a natural anticoagulant (Latin: cogere, “to curdle”) produced via effects of mold on coumarin, occurs as a fragrant chemical compound characteristic of White Sweet Clover’s genus, Melilotus (Ancient Greek: μέλι, méli, “honey” + λωτός, lōtós, “lotus”). Melilotus officinalis serves as a forage source for livestock and also as a nectar source for apiaries (Latin: apis, “bee”), places for keeping beehives. Melilotus officinalis promotes soil-building via nitrogen-fixing, which converts relatively inert atmospheric nitrogen into nitrogen compounds essential for soil fertilization.

Melilotus albus is known commonly in English as Bokhara clover, honey clover, tree clover, white-flowered sweet clover, white sweet clover or white melilot.

In its first year, White Sweet Clover may hover around 3 feet (0.9 meters) in height. Above ground, its vegetative silhouette features clover-like leaves alternating in a trio of leaflets along the small, branched stem. Underground, it develops a healthy root system.

In its second, and usually final, year, the biennial flowers and easily may reach maximum heights of over 6.5 feet (2 meters).

Blooming from May through October, tiny, white flowers present a pea-like floral appearance typical of members of the bean, legume, or pea family of Fabaceae (Latin: faba, “bean, horse bean”). Two large, erect petals and two keeled, or prow-shaped, lower petals enclose reproductive organs, pistil and stamens.

Attached by pedicles (Latin: pediculus, “footstalk, little foot”; from pes, “foot”), or small stalks, flowers densely crowd the upper 3-plus inches (8-plus centimeters) of elongated stems that emerge as axillary racemes (Latin: racemus, “cluster”; Ancient Greek: ῥάξ, rháks, “grape”) from cradles formed by the axil, or angle, between the leaflet trios and the stem.

White Sweet Clover’s sweet fragrance, which is released via crushing or cutting, belies the plant's bitter taste. Responsible for the sweet fragrance, coumarin contains the bittersweet ability to be transformed via fungal metabolites in spoiled harvests into a powerful anticoagulant, dicoumarol, that may induce fatal internal hemorrhages in livestock.

White Sweet Clover abundantly lines the western edge of the dirt path that meanders through the sunny meadow extending from my yard's southern border.

Standing tall at heights ranging from 3 feet to over 5 feet (0.9 to 1.5 meters), White Sweet Clover keeps company with other naturalized, Old World pasture legumes: pink-and-white flowered crown vetch (Securigera varia), dark-pink flowered red clover (Trifolium pratense), pinkish-white flowered white clover (Trifolium repens) and golden flowered relative, Yellow Sweet Clover (Melilotus officinalis).

With over six dozen, or 72, plants proliferating along the meadowy path, White Sweet Clover easily outnumbers Yellow Sweet Clover, represented by one prominent trio, at a strong ratio of 24 to 1. Despite the disparity in numbers, both sweet clover species, White and Yellow, appear healthy.

Despite their sometimes negative reputation as invasive weeds, both sweet clovers prettify the meadowy palette with pure whiteness and sunny yellowness.

Melilotus albus in wash at junction of state routes (SR) 157 and 158, Kyle Canyon, Spring Mountains, southern Nevada: Stan Shebs, CC BY SA 3.0, via Wikimedia Commons

Acknowledgment

My special thanks to talented artists and photographers/concerned organizations who make their fine images available on the internet.

Image credits:

Holly Blue Butterfly (Celastrina argiolus) nectaring on White Sweet Clover (Melilotus albus), Weinsberg, Baden-Württemberg state, southwestern Germany: Rosenzweig, CC BY SA 3.0, via Wikimedia Commons @ http://commons.wikimedia.org/wiki/File:Celastrina_argiolus_Weinsberg_20070708_3.jpg

Melilotus albus, Spring Mountains, southern Nevada: Stan Shebs, via Wikimedia Commons @ https://commons.wikimedia.org/wiki/File:Melilotus_albus_3.jpg

For further information:

Marriner, Derdriu. "Yellow Sweet Clover: Golden Flowers of Fragrant Melilotus officinalis." Earth and Space News. Saturday, May 30, 2015.
Available @ https://earth-and-space-news.blogspot.com/2015/05/yellow-sweet-clover-golden-flowers-of.html

"Melilotus albus Medik." USDA Germplasm Resources Information Network (GRIN) > GRIN Taxonomy for Plants > Taxon.
Available @ http://www.ars-grin.gov/cgi-bin/npgs/html/taxon.pl?23989

"Melilotus alba, Melilotus officinalis." US Forest Service > Fire Effects Information System (FEIS) Database > Plants > Forb.
Available @ http://www.fs.fed.us/database/feis/plants/forb/melspp/all.html

“Pea-like.” Sunny Gardens > Garden Glossary.
Available @ http://www.sunnygardens.com/garden_glossary/pea-like/pea-like_000430.php

Tenaglia, Dan. “Melilotus albus Desr.” Missouri Plants > White flowers, Leaves alternate.
Available @ http://missouriplants.com/Whitealt/Melilotus_alba_page.html

“White and Yellow Sweet Clovers Melilotus albus and M. officinale.” Missouri Department of Conservation > Discover Nature > Field Guide.
Available @ http://mdc.mo.gov/discover-nature/field-guide/white-and-yellow-sweet-clovers