Trifolium pratense (Pink clover)

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Trifolium pratense L.

Pink clover

Kingdom	Plantae	Plants, but not fungi, lichens, or algae
Subkingdom	Tracheobionta	Vascular plants—plants with a “circulatory system” for delivering water and nutrients
Division	Magnoliophyta	Flowering plants, also known as angiosperms
Class	Magnoliopsida	Dicotyledons—plants with two initial seed leaves
Subclass	Rosidae	Roses, legumes, proteas, dogwoods, hydrangeas, mistletoes, euphorbias, grapes, many more
Order	Fabales	Legumes (pea and bean families)
Family	Fabaceae	Legume family (peas and beans)
Genus	Trifolium	“Three-leaved,” for the 3-leaf clusters
Species	pratense	Growing in meadows

About plant names...

Red clover is native to Europe, western Asia, and northwest Africa. It was brought to North America (and many other places), and it is now abundant. Red clover is grown extensively for pasture animals.

Here is a comparison among red, white, alsike, and crimson clovers:

Appearance in late fall. · 9/3/2009 · Nashua River Rail Trail, Ayer, Massachusetts · ≈ 5 × 3½″ (13 × 9.2 cm)

8/4/2009 · Near Nashoba Hospital, Ayer, Massachusetts · ≈ 5 × 3½″ (13 × 8.8 cm)

	*Trifolium repens*	*Trifolium hybridum*	*Trifolium incarnatum*
Common Name	white clover	alsike clover	crimson clover
Plant	Plant stems are 4-16″ (10-40 cm) long, but often lying on their sides, so these clovers are usually close to the ground	1-2′ (30-60 cm) tall, typically somewhat smaller than red clover and larger than white clover. It has multiple hairless, fairly flexible stems	1½′ (50 cm) high.
Flowers	On flower stalks 1-4″ (2.5-10 cm) long. Flowerheads are ½-1¼″ (1.3-3.2 cm) around, rounded, white, sometimes pinkish	½-¾″ (1.3-1.9 cm) around, and may be pink on the bottom, grading to white on the top; or pink throughout. The shade of pink is lighter than with red clover	Deep red, forming rounded conical flowerheads about 1″ (2.5 cm) tall and ⅝″ (1.7 cm) around. Flowering occurs during April to May.
Leaves	In groups of 3. Leaflets are oval, ½-1¼″ (1.3-3.2 cm) long, with a slight indentation at the end. Each leaflet has a pale green "V" close to the base and slightly toothed leaf edges	In groups of three, each about ¾″ (2 cm) long, and attached directly to the stem that supports the leaf cluster. Leaves are oval-shaped, with smooth-appearing edges that have tiny teeth, and no chevrons	Leaves are round or oval, in groups of three, each roughly at right angles to the others.
Range/ Zones
Habitats	Waste ground, pastures, open fields, roadsides, railroads	Moist meadows near woodlands, pastures, abandoned fields, and roadsides
Type	Wild	Wild	Wild
Occurrence	Very common	Common, but less so than red and white clovers

Identification: Plants are 8-31″ (20-80 cm) tall, multiply branched, often partially lying down. Stems are sometimes purplish and sometimes hairy. Leaves are in 3-leaf clusters. Leaflets ⅜-2½″ (1-7 cm) long × ⅜-1½″ (1-4 cm), with a distinctive pale green crescent or "V" on the outer half of the leaf. They vary from roundish to an elongated oval. Flowers are pink to rose (rarely white). Flowerheads are about ¾″ (1.9 cm) around.

Medical: As is typically the case with very common plants, various healing properties have been attributed to red clover. One of the more widely believed properties is that clover contains substances that can treat post-menopausal symptoms. A controlled study by the George Washington University School of Medicine, published in the journal Menopause, found that clover has no such effect.

But as a fertilizer...

Rolling your own fertilizer

Nitrogen is one of the essential building blocks of all life. There is no shortage of nitrogen—it makes up almost four fifths of our atmosphere—but neither plants nor animals can use it directly in its atmospheric form (N₂). It takes energy to convert it to a usable form, for instance, to ammonia or nitrates. Energy from lightning, for example; or energy from the vast amounts of electricity used to create commercial nitrate fertilizers. If a plant could somehow harvest nitrogen directly from the air, it would be able to make its own fertilizer, allowing it to colonize soils that were too poor in nutrients for other plants.

Legumes, including alfalfa, clover, peas, beans, lentils, soybeans, and peanuts, have managed exactly this stunt, called "nitrogen fixing"—and without even solving the problem themselves. Instead, they brokered an amazing agreement with the real inventors of nitrogen fixing: symbiotic bacteria known as Rhizobia. The bacteria grow in nodules on the roots of legumes, supplying the plant with usable nitrogen in return for malates and succinates for energy and carbon. The bacteria combine nitrogen, hydrogen, and electrons like this:

N₂ + 8H⁺ + 8e^– → 2NH₃ + H₂

We could write this more simply as:

nitrogen + hydrogen + electricity → ammonia + hydrogen

The eight hydrogen ions (8H⁺) in this reaction come mostly from water vapor. The electrons (8e^–) can be thought of as electricity created by the bacteria. The results of the reaction include ammonia (NH₃) and hydrogen (H₂).

The created hydrogen reacts pretty quickly with oxygen, forming more water vapor. And the ammonia is very close to what the plant needs. In water, ammonia quickly reacts with hydrogen ions in the water to create ammonium ions:

NH₃ + H⁺ → NH₄⁺

ammonia + hydrogen ions → ammonium ions

You are already familiar with this reaction—it is the same one that makes you wrinkle your nose in disgust when you catch a whiff of ammonia. But what smells bad to you is a critical nutrient to most plants.

The ammonium ions created by the bacteria are absorbed directly by the roots of the legumes. The trapped nitrogen feeds the plant, with enough left over after the plant dies to foster the growth of other plants as well. Thus legumes are sometimes called green manure.

So before you get too irritated with the clover growing in your lawn, consider that it is busy fertilizing your lawn.

Online References:

The Oregon Flora Image Project

in Paghat's Garden

Wikipedia

Plants for a Future, a resource and information centre for edible and otherwise useful plants

Hort.purdue.edu

The Virginia Tech Weed Identification Guide