Alsike clover (Trifolium hybridum)

Synonyms: Trifolium elegans

Common Names: Swedish clover, hybrid clover, alsike

Description:

Alsike clover (Trifolium hybridum) is a low clover from Europe and Asia, brought to North America as a forage and cover crop and now naturalized across the continent [1][2]. It grows along roadsides, in pastures, and in moist meadows, and is reportable to MISIN as a non-native species [2]. Its most serious problem is to animals: eating alsike clover can poison horses, causing skin damage and liver disease [3].

Habit:

Alsike clover is an upright clover that grows 1 to 2 feet tall on smooth, hairless stems [1]. Like other clovers, each leaf is divided into three small leaflets ? here about half an inch long, with finely toothed edges and, importantly, no pale "V" or watermark across them [1]. From early summer into fall it produces rounded flower heads about half to three-quarters of an inch across, each packed with tiny pea-like florets that are pink at the bottom and fade to white toward the top [1]. The clearest clue is that each flower head sits on its own stalk that rises above the leaves, rather than nestling right against a pair of leaves the way red clover does [1]. It is easiest to spot in summer when it is in bloom in damp meadows, pastures, and roadside ditches [1].

At-a-glance cues:

1. Rounded pink-and-white flower heads, about 1/2 to 3/4 inch across, on stalks held above the leaves [1]
2. Three toothed leaflets with no pale "V" or watermark (unlike red clover) [1]
3. Smooth, hairless, upright stems 1 to 2 feet tall that do not creep and root along the ground [1]
4. Grows in moist meadows, pastures, and roadsides; blooms summer into fall [1]

Leaves:

1. Divided into three leaflets (typical clover leaf), each about 1/2 inch long [1]
2. Leaflets are oval, hairless, with finely toothed (serrated) edges [1]
3. Plain green and unmarked ? no pale chevron or watermark like red clover has [1]
4. Borne on the stems rather than rising from the base of the plant [1]

Stems:

1. Herbaceous (not woody); upright to ascending, 1 to 2 feet tall [1]
2. Round, hollow, and hairless, branching occasionally [1]
3. Do not creep along the ground or root at the joints (unlike white clover) [1]

Flowers:

1. Tiny pea-like florets (30 to 50) packed into a rounded head about 1/2 to 3/4 inch across [1]
2. Pink at the base grading to white toward the top, or pink throughout ? paler than red clover [1]
3. Each head sits on its own stalk (peduncle) held above the leaves, not pressed against a pair of leaves [1]
4. Bloom from early summer into fall; each floret is perfect (has both male and female parts) [1]

Fruit and seeds:

1. Fruit is a small, short, broad pod, greenish-brown darkening to nearly black as it ripens [1]
2. Pods do not split open on their own when ripe [1]
3. Each pod holds a few tiny seeds [1]
4. Seeds spread in hay and forage, in soil, and on mowing and farm equipment [1]

Habitat:

Alsike clover grows in open, sunny, damp places ? moist meadows near woods, pastures, hayfields, abandoned fields, ditches, and roadsides [1]. It handles a wide range of soils and does especially well on moist clay and loam, tolerating wetter and more acidic ground than many other clovers [1]. It is native to Europe and Asia and was introduced to North America as a forage legume and cover crop, and it is now naturalized across the United States and Canada [1][2].

Reproduction:

Alsike clover spreads by seed [1]. Because it is grown for hay and forage, its seed travels easily in hay, in dropped or sown seed mixes, on mowing equipment, and in soil moved between sites [1]. Bees and other insects visiting the flowers move pollen from head to head [1]. A planted patch can seed itself into nearby ditches, meadows, and pastures.

It is a short-lived perennial that can also behave like an annual or biennial, flowering from early summer into fall [1]. The pods do not pop open on their own, so most seed simply drops near the plant or is carried off in hay and on equipment [1]. For control, the key is timing ? mow or pull plants before the flower heads ripen into seed in summer, so they cannot add to the seed already in the soil [1].

Impact and Damage:

The biggest concern with alsike clover is its danger to horses [3]. Horses that graze pastures or eat hay containing alsike clover can develop two problems. The first is photosensitivity ? a severe sunburn-like reaction where light-colored skin, especially on the face and legs, becomes red, thickened, and crusted [3]. The second is liver damage, sometimes called "big liver disease," which can be serious or fatal and may show up as weight loss, a poor coat, and neurologic signs such as listlessness, head-pressing, and stumbling [3]. Dark-haired horses can suffer liver damage even without visible sunburn [3]. The trouble is linked to a mold called black blotch (Cymodothea trifolii) that grows on the clover's leaves in wet, humid conditions, so risk is highest in damp summers and low, humid pastures [3].

For people and most other animals, alsike clover is not a notable hazard, and it is not a garden or structural pest [3]. As an introduced plant it does spread into moist meadows, ditches, and pastures and can mix into or crowd low native ground cover in those wet, disturbed places, though it is valued elsewhere as a forage and pollinator plant [1][2].

Similar species:

Alsike clover is easily confused with other clovers. Telling them apart matters because two look-alikes are protected native plants, and because alsike clover is the one that poisons horses.

White clover (Trifolium repens) is the most common look-alike, with similar white-to-pink rounded heads. But white clover creeps low along the ground and roots at the joints, and its flower heads rise on bare stalks straight from the ground. Alsike clover stands upright on leafy stems and does not root as it spreads [1].

Red clover (Trifolium pratense) has larger, deeper pink-purple heads that sit right against a pair of leaves with no stalk, hairy stems, and a pale "V" watermark on each leaflet. Alsike clover has smaller, paler pink-white heads on their own stalks, smooth hairless stems, and unmarked leaflets [1].

Running buffalo clover (Trifolium stoloniferum) is a rare native clover that spreads by above-ground runners and carries a pair of leaves right below each white flower head. Alsike clover grows upright without runners and holds its heads on stalks above the leaves [1].

Buffalo clover (Trifolium reflexum) is another native clover; its two-toned red-and-white florets bend downward as the head ages, and a pair of leaves sits just below the head. Alsike clover's florets do not strongly bend back, and its heads are raised above the leaves on a stalk [1].

Monitoring and rapid response:

Signs to watch for:

1. Low, upright clover with pink-and-white rounded flower heads on stalks above the leaves, in summer [1]
2. Three toothed leaflets with no pale "V" mark, on smooth hairless stems [1]
3. Patches in moist meadows, pastures, hayfields, and roadside ditches [1]
4. In horse pastures, dark blotches on the underside of clover leaves in damp, humid weather (the mold linked to poisoning) [3]

What you can do:

1. Hand-pull or dig out small patches, including the roots; this is easiest when the soil is moist [1]
2. Mow plants before the flower heads ripen into seed in summer to stop new seed from forming [1]
3. Bag and dispose of seed heads rather than composting them on site [1]
4. If you keep horses, fence them out of clover-rich pastures in wet years and humid spells, and mow or thin clover and improve drainage to cut down the mold linked to poisoning [3]
5. Natural area crews can reduce larger stands by repeated mowing before seed set across a site, and should remove small, outlying patches first [1]

When to call a professional:

1. Large or well-established stands in pasture or natural areas that keep reseeding [1]
2. Horse pastures where alsike clover is widespread and poisoning is a risk ? consult a veterinarian and a pasture or extension specialist [3]
3. For chemical control options, contact a licensed applicator or your local cooperative extension office.

Report sightings to MISIN. Help track this species' spread by submitting observations through the MISIN web site or the MISIN mobile app (Android, iOS, Windows, and macOS). Photos at multiple angles paired with a precise GPS location are the most valuable data for confirming new occurrences and triggering rapid-response review.

Credits:

1. North Carolina State Extension Gardener Plant Toolbox. Trifolium hybridum (Alsike Clover). plants.ces.ncsu.edu
2. USDA NRCS PLANTS Database. Trifolium hybridum L. (TRHY). plants.usda.gov
3. University of Minnesota Extension. Feeding clover to your horse. extension.umn.edu

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