This section is from the book "British Wild Flowers - In Their Natural Haunts Vol2-4", by A. R. Horwood. Also available from Amazon: A British Wild Flowers In Their Natural Haunts.
Photo. Flatters & Garnett - Hop Trefoil (Trifolium procumbens, L.)
The specific name suggests the trailing habit of most of the stems, the principal one being erect, slender, the leaflets blunt at the tip, the leaves with lobes each side of a stalk, the leaflets in threes, and the stems are also slightly downy.
The flowerheads are round, large, in oval spikes, with overlapping florets, having a hop-like appearance (hence the name). When the flowers are withered the standard yellow, like the rest of the flowers, is arching but does not fold over the pods. It is bent down, does not fall, and is furrowed. The flowers are stalked, the style is less than the pod, the leaf-like organs on the leaf-stalks are 1/2 - ovate, acute, and the seeds are oval.
The stems are rarely 18 in. long, and usually 1 ft, and on the coast about 6 in. high, with larger flowers. The flowers are in bloom in June and July. The plant is annual.
The flowers are large and conspicuous, and are visited by bees, Apis mellifica, Halictus flavipes. The tube is not so long as in Red Clover, the flowers numerous and dense. The standard is broad, and arches over the centre, and the style is hooked. The short calyx allows the other parts of the flower to return to position after an insect visit.
The pod is a 1-seeded fruit, not splitting into many parts, egg-shaped, and when ripe it falls off or is broken off. It is therefore dispersed by its own agency.
Hop Trefoil is addicted to a sand soil. Like Hare's Foot Trefoil, it also grows on the more ancient rock formations on stony barren ground.
It is a food plant for a beetle, Apion pisi, and a moth, Anthocera trifolii.
The second Latin name refers to its procumbent or trailing habit It is called Hop or Yellow Clover, and Hop Trefoil. From the hoplike shape of the flowers it is called Hop Trefoil. Not so valuable as Red or White Clover, it is an annual. It often covers barren ground where nothing else will grow.
Essential Specific Characters: 82. Trifolium procumbens, L. - Stem erect, branches procumbent, leaflets obovate, central petiole longest, stipules ovate, flowers yellow, in dense, round, hop-like heads, forty flowers, standard dilated not folded.
Bird's Foot Trefoil (Lotus corniculatus, L.)
This plant, which is known only, as regards its distribution, as a member of the flora of the North Temperate Zone to-day, is a native of Europe, N. Africa, N. and W. Asia. In Great Britain it is found in every part, as far north as the Shetlands, growing at a height of 2800 ft. in the Highlands. It is found in Ireland and the Channel Islands.
The common Bird's Foot Trefoil forms clumps and patches of golden colour in the meadows from June till late in the summer. There it is associated with Yellow Rattle, the Daisy, the Ox-eye, Daisy, and other widespread pratal species, growing luxuriantly also on banks, such as railway embankments or cuttings.
The slender, numerous stems grow in close clusters, and are branched, the leaflets, which are in threes, are egg-shaped and smooth, but hairy here and there. The stems are half-erect and somewhat square-stalked. The leaflets are only shortly stalked. The stipules (in pairs) are narrowly elliptical, ending in a point.
The flowers vary in colour from red to lemon colour, and in number from 5 to 10, but are usually golden yellow, and borne on short flowering branches, in a sort of umbel, the heads being bent down. The calyx is not quite half as long as the corolla, and at first the teeth are pressed together and erect, and are triangular below, awl-shaped above, the points of the two upper teeth meeting together. The pods are cylindrical, separated by divisions between the seeds, and two-valved.
Photo. B. Hanley - Bird's Foot Trefoil (Lotus corniculatus, L.)
Sometimes the plant is a foot or more in height, but usually 4-6 in. The flowers may be seen from May to September. Bird's Foot Trefoil is perennial.
In this common flower we have a type of the relation of parts to insect visits typical of flowers like the Pea in general. There are five petals, of which the upper is erect and called the standard. Below these are the two wings or alae. The other two lower petals are united along the anterior margin to form a carina or keel.
The nine stamens are united at the base to form a tube encircling the pistil, and project beyond it into a triangular cavity at the bottom of the keel which is a repository for pollen. The tenth is free. The alae are locked by projecting knobs fitting into a hollow opposite (as in the mantle of a Sepia or Cuttle-fish). An insect alighting on the flower bears down the alae and the keel, which is pushed over the column or ring of stamens and forces the pollen up into the cavity and against the abdomen of the insect, and when the insect goes off to another flower the parts return again to their former position and cover up the pollen. The bee is able to reach the honey when the tenth stamen is free. In other species of Leguminosae where the tenth stamen is united there is usually no honey.
Pollen is discharged when the anthers burst before the flowers are opened. Of the two groups of five stamens one has thickened ends, and after the five inner anthers have shrivelled they fill the hollow in the keel in which the pollen is collected. The wings and keel are both depressed when a bee alights, and being locked together they spring back as by a "piston mechanism" after pressure is removed.
The visitors are Hymenoptera (Apidae), Diptera, Sphinges, Sesia, Zygaena, Bombyces, Porthesia, Noctuae, Euclidia, etc.
The pod is a many-seeded fruit, and is divided into divisions which alternate with the seeds, and as the chambers break off when the pod is ripe, the seeds travel to a short distance, and the Bird's Foot Trefoil is therefore extended in range by its own agency.
This plant is best suited by a sand soil in which there is a fair proportion of clay, or sandy loam, and is therefore both a sand-lover and a clay-lover. It is abundant on Triassic and Liassic clays as well as on later Oolitic rock soils.
The fungi Peronospora trifoliorum and Uromyces striatus attack Lotus. The beetles Apion loti, Bruchus loti, Meligethes solidus, a hymenopterous insect Megachile argentata, and the Lepidoptera, Dusky Skipper, Wood White, Common Blue, Clifden Blue, Common Heath, Gelechia tumidella, G. taeniolella, Nepticula cryptella, Silver Cloud (Xy/omyges conspicillaris), etc, Transparent Burnet (Zygaena minos), Broad-bordered Five-spotted Burnet (Z. trifolii), Narrow-bordered Five-spotted Burnet (Z. lonicerae), Lithosia palliatella, Coleophora discordella, Bordered Gray (Selidosema plumaria), and Myllophila semi-rubella, and the fly Diplosis loti feed on it.
Lotus, a name given by Theophrastus, is the Latin for this common plant, and the second Latin name means shaped like a little horn, referring to the fruit, from the Latin corniculum, a little horn. It is called Bird's-foot, Bloom-fell, Boots-and-Shoes, Feal Broom, Butter-and-Eggs, Butter-jags, Cat cluke, Claver, Cat-poddish, Cat's Claws, Cat's Clover, Cheese-cake, Craw-taes, Crow-foot, Crowtaes, Cuckoo's Stockings, Lady's Cushion, Dead Man's Fingers, Devil's Claws, Devil's Fingers, Eggs-and-Bacon, Fell-bloom, Fingers-and-Thumbs, Fingers-and-Toes, God Almighty's Thumbs-and-Fingers, Ground Honeysuckle, Hen-and-Chickens, Jack-jump-about, King Finger, Lady's Boots, Lady's-finger-Grass, Lady's Glove, Lady's Shoes and Stockings, Lady's Slipper, Lamb's Sucklings, Patten and Clogs, Milkmaid, Pig's Foot, Pig's Pettitoes, Sheep Foot, Tommy Tottles, etc. The name Cat cluke or Cat-luke is applied from a supposed resemblance it has to a cat's or bird's foot.
The yellow Lambtoe I have often got Sweet creeping o'er the banks in sunny time.
It is a valuable meadow plant, and will grow freely and luxuriantly in damp spots. Mixed with other plants and grasses it affords good fodder for cattle and horses.
Essential Specific Characters: 84. Lotus corniculatus, L. - Stem prostrate, leaves smooth, obovate, stipules ovate, flowers in an umbel, 5-10, yellow, calyx teeth appressed, points of two upper teeth converging, erect in bud.