White Sweet Clover (Melilotus albus) — identification, habitat & look-alikes

White sweet clover is a tall, sweet-scented with slender spikes of tiny white flowers, now found in every US state. Brought to North America long ago as livestock forage and long planted by beekeepers and farmers as a nectar plant and soil builder, it is now treated as an invasive weed of prairies and other open natural areas. Despite the name, it is not a true clover.

Appearance

Appearance: Grows about 3 ft (1 m) tall in the first year and 4–5 ft (1.2–1.5 m) in the second. Second-year plants look bushy and well branched.
Growth form: A : in its first year it makes leaves and a deep taproot, and in its second year it flowers, sets seed, and dies. Like other legumes, it hosts root bacteria that fix nitrogen.
Leaves: Alternate leaves made of three finely toothed leaflets, each longer than it is wide.
Flowers: Tiny white pea-like flowers, about 1/8–1/4 in (3–6 mm) long, crowded on slender spikes. The flowers are fragrant.
Flowering time: Blooms from about May into September or October in Missouri and June to October in Alaska.
Fruit: Small egg-shaped pods ripen black to dark gray, usually holding one yellow seed.

Look-alikes

Yellow sweet cloverMelilotus officinalis

Yellow sweet clover has yellow flowers. It also tends to grow on drier sites and starts blooming 2–4 weeks earlier.

Why they get mixed upThe two often grow together and look nearly identical apart from flower color.

AlfalfaMedicago sativa

Young sweet clover seedlings look like alfalfa, but their leaflets have no hairs on the underside.

Why they get mixed upBoth are legumes with three-part leaves.

Where it lives

Typical habitats: Roadsides
Abandoned fields
Pastures
Prairies
River gravel bars
Range: Native to southern Europe, much of Asia, and northeastern Africa. In North America it occurs in every US state and all but two Canadian provinces. In Alaska it has spread along river bars in the interior, south-central, and southeast parts of the state.
Preferred conditions: Needs sun and does not tolerate dense shade. Prefers limy or loamy soils and handles some salt and hard cold (down to about −38 °F / −39 °C), but not flooded ground.
Flowering: Flowers May–Oct
Flowers May–Oct

Life cycle

Seed dispersal: One plant makes a very large number of seeds, and seeds can stay alive in the soil for decades. Seeds travel with water, on vehicle tires, and as a contaminant in grain.

Cautions

Cautions: The sweet smell, stronger when dried, comes from , which can be toxic to animals. The plant also contains dicoumarol, a substance that keeps blood from clotting.

Name and classification

About the name: Some botanists treat it as a white-flowered form of yellow sweet clover (Melilotus officinalis), but most keep the two as separate species. Older references often spell it Melilotus alba.

Conservation

IUCN Red List: NENot EvaluatedNot yet assessed
Status: Missouri and Alaska treat it as an invasive plant. It shades out native prairie plants and adds nitrogen to the soil, and fire wakes up its long-lived seeds.