Fabaceae: Pea Family — Trifolium (Clover) : Heads without an involucre

The pea family has 5-petaled flowers, consisting of a wide upper banner petal, two wing petals, plus two lower petals which are fused to form a boat-shaped keel.  Many genera have flowers in heads or spikes, comprising many individual flowers.  Examples are lupines and clovers.  The seed pod is generally a “legume”.  This is a long, flattish pod, swollen by the seeds, and splitting lengthwise along both the top and bottom.

Clovers are common, small plants, sometimes with subtle differences.  In reading a description of a clover, it is important to remember that the flower head is made up of many small individual flowers.  So if a description says that the calyx lobe is longer than the flower, it is the individual flower one must examine, not the whole head.  Identifying clovers is simplified by looking to see if they have an involucre: bracts at the base of the head which are fused to form a cup, bowl or wheel.  About 40% of the clovers found in Monterey County have involucres; interestingly all of these are native.  This page covers the clovers that do not have an involucre; the first four on the page are native, all of the others are non-native.

Rancheria / Indian Clover – Trifolium albopurpureum

Blooms:

Mar–June

Plant Height:

Small

Flower Size:

Medium

Origin:

Native

Habitat:

Open grassy areas

Notes:

This small clover can appear in profusion.  Flowers are noticeably woolly, purple with a pale pink tip, borne on long peduncles.  Not to be confused with Rose Clover (Trifolium hirtum, see below), which has much larger pure pink flowers, subtended by 1 or 2 small leaves, each with several leaflets.

Narrow-leaved Clover – Trifolium angustifolium

Blooms:

May–June

Plant Height:

Medium

Flower Size:

Large

Origin:

Mediterranean

Habitat:

Open grassy areas

Notes:

An increasingly common clover, so much so that one clover expert remarked “here today, the world tomorrow”.  Sometimes found in large quantities.  It is distinguished by its tall, 1–5 cm cylindrical spike of pink flowers, which fade to orange after pollination.  Its narrow, strappy leaflets are distinctive, 2–4.5 cm long.  The calyx lobes are sharp-tipped, and harden in fruit, making the fruits quite prickly to the touch.

Rabbitfoot Clover – Trifolium arvense

Blooms:

June

Plant Height:

Medium

Flower Size:

Large

Origin:

Europe

Habitat:

Open grassy areas

Notes:

Similar to Narrow-leaved Clover (Trifolium angustifolium, see above), but with a smaller (1–3 cm) ovate to short-cylindric inflorescence.  The calyx lobes are narrow and densely hairy, much longer than the pale pink to white flowers.  This gives the inflorescence a distinctly bristly appearance, although it is soft to the touch.  Leaflets are less than 2 cm long, oblong to oblanceolate.  Stipules are red-striped and similar to those of Rose Clover (Trifolium hirtum, see below), but narrower.

Hop Clover – Trifolium campestre

Blooms:

April–May

Plant Height:

Small-medium

Flower Size:

Medium

Origin:

Europe

Habitat:

Open grassy & waste areas

Notes:

This and Shamrock Clover (Trifolium dubum, see below) are the only two clovers found in the county which have yellow flowers; both are weedy immigrants from Europe.  This has much larger (though still small) flowers heads, generally with 20 individual flowers.  The banner has distinct veins.

Tree / Foothill Clover – Trifolium ciliolatum

Blooms:

Mar–June

Plant Height:

Medium

Flower Size:

Medium

Origin:

Native

Habitat:

Open grassy areas

Notes:

This and Pinpoint Clover (Trifolium gracilentum, see below) are easily confused, both having flowers that become reflexed as the inflorescence matures.  Also, both may exhibit the same “pinpoint” (the tip of the axis which becomes visible as the flowers reflex).  This species is most easily distinguished by the short bristles on the calyx (the calyx of Pinpoint Clover is glabrous).  Its leaflets are longer (1–2 cm) and more slender.

Shamrock / Little Hop Clover – Trifolium dubium

Blooms:

May–July

Plant Height:

Small

Flower Size:

Small

Origin:

Europe

Habitat:

Open grassy & waste areas

Notes:

This and Hop Clover (Trifolium campestre, see above) are the only two clovers found in the county which have yellow flowers; both are weedy immigrants from Europe.  This has much smaller and quite distinctive flower heads, with 5–10 individual flowers arranged in umbels.  Leaflets are obovate and finely toothed.

Strawberry Clover – Trifolium fragiferum

Blooms:

Mar–Aug

Plant Height:

Small

Flower Size:

Small

Origin:

Europe, Africa

Habitat:

Escape from cultivation, disturbed areas

Notes:

This clover is unusual because of the appearance of the fruiting body.  The flower head is unremarkable, about 1 cm across, with pale pink flowers subtended by green involucral bracts which remain free.  As the flowers mature, the calyxes inflate so that the fruiting head is said to resemble a strawberry, though somewhat fuzzier than the real thing.  Also, it’s a little pricklier, because of the two bristle-like calyx lobes extending below the opening of each inflated calyx.

Clustered Clover – Trifolium glomeratum

Blooms:

Mar–May

Plant Height:

Small

Flower Size:

Small

Origin:

Europe

Habitat:

Disturbed areas

Notes:

Uncommon, but can spread rapidly once it becomes established. The flower heads are sessile, either at the stem tip or in leaf axils.  Individual flowers are pale pink, each with a calyx comprising a pair of triangular sepals with recurved tips.  Leaflets are about 1 cm long and obovate.

Pinpoint Clover – Trifolium gracilentum

Blooms:

Mar–June

Plant Height:

Medium

Flower Size:

Medium

Origin:

Native

Habitat:

Open disturbed, dry or moist areas

Notes:

This and Tree Clover (Trifolium ciliolatum, see above) are easily confused, both having flowers that become reflexed as the inflorescence matures.  Also, both may exhibit the same “pinpoint” (the tip of the axis which becomes visible as the flowers reflex).  This species is most easily distinguished by its glabrous calyx (the calyx of Tree Clover is clearly bristly).  Its leaflets are smaller (< 1.5 cm) and broader, with a shallowly notched tip.

Rose Clover – Trifolium hirtum

Blooms:

Apr–May

Plant Height:

Medium

Flower Size:

Medium

Origin:

Eurasia

Invasive?

Yes – limited

Habitat:

Disturbed areas, roadsides

Notes:

The only invasive non-native clover, but it is often found in great quantities. The flowers are attractive, distinctly hairy and pale to dark pink in color. The inflorescence is typically subtended by 1 or 2 leaves, each with 2 or 3 leaflets. Each petiole is subtended by a broad, pink-striped stipule.  Photo #3 by Cliff Halverson.

Clover, Rose

Crimson Clover – Trifolium incarnatum

Blooms:

May–Aug

Plant Height:

20–50 cm

Flower Size:

Large

Origin:

Europe

Habitat:

Fields and waste places

Notes:

The brilliant crimson inflorescence spikes of this clover are unmistakable.  Individual flowers are longer than the calyx lobes.  Despite the name, this species occasionally has white flowers.

Macrae’s Double-headed Clover – Trifolium macraei

Blooms:

Mar–May

Plant Height:

Small

Flower Size:

Small

Origin:

Native

Habitat:

Grassy places near coast, dunes

Notes:

A low-growing clover with decumbent to erect stems.  It is most easily recognized by its paired heads, generally sessile but sometimes with one head on a short peduncle.  Individual heads are < 1 cm across with purple or bicolored flowers. The calyx is hairy and subtended by one leaf with 3 leaflets.  Leaflets are narrowly elliptic to ovate, 1–2 cm long.

White Clover – Trifolium repens

Blooms:

Feb–Dec

Plant Height:

Medium

Flower Size:

Large

Origin:

Eurasia

Habitat:

Escape from cultivation, moist areas or grassland

Notes:

This is often found as a lawn weed.  Its pure white flowers, with their long flowering season, are easily recognized.  The plant has creeping stems that root at the nodes, unlike Alsike Clover (Trifolium hybridum), which also has pure white flowers but with a sprawling to erect growth habit.

Subterranean Clover – Trifolium subterraneum

Blooms:

Mar–Apr

Plant Height:

Prostrate

Flower Size:

Small

Origin:

Southern Europe, North Africa

Habitat:

Meadows, roadsides

Notes:

This is an unusual clover, since it has flowers of two kinds.  The outer flowers, rather lotus-like in appearance, are white with pink veins, and a distinct maroon ring at the base of the calyx lobes.  These are fertile.  In addition, it has sterile flowers which lack petals, and have a stalk-like calyx with bristles at their tips, which recurve to form a kind of bur.  Close examination is needed to discern these.