Nightmare or daydream, here’s clover’s backstory
To make a prairie it takes a clover and one bee.
One clover, and a bee,
The revery alone will do,
If bees are few.
– Emily Dickinson
What would Miss Dickinson have known of the prairie, that immense sweep of unbroken grasslands that once stretched from the Dakotas through Nebraska, Kansas and Oklahoma and westward through the Great Plains to the feet of the Rocky Mountains?
No matter; her prairies, though perhaps confined to the three acres of her father’s property in Amherst and cow pastures seen en route to Boston and Philadelphia during her youthful traveling days, were enough.
One clover and a bee will do … or revery alone, if bees are few.
By the time she was born in 1830, the sight of a honey bee bending the orbed head of a white clover would have been, as today, a metaphor for an idyllic summer day. And yet, two centuries beforehand, North America was home to neither species.
Although pre-Columbian Native Americans were adept agriculturalists, there is no record of their having kept livestock and they had no use for forage crops. Across the Americas, the plants they chiefly cultivated – maize, pumpkin, cassava, beans and sweet potatoes – were for human consumption. But the face of the landscape was soon to change.
In 1972, historian A. J. Crosby, Jr. published “The Columbian Exchange,” a comprehensive overview of the ecological and cultural impacts – in the New World and the Old – of Europeans’ exploration, conquest and exploitation of the Americas in the decades following their discovery by Columbus in 1492.
Cattle, chickens, donkeys, pigs, domestic sheep and goats, Europeans’ accustomed livestock did not exist in North America prior to being introduced by the first colonists, and honey bees reportedly were introduced to the continent in 1622.
Although the diverse vegetation of the tallgrass prairies in the heart of North America would have served admirably as fodder for the colonists’ livestock, the grasses and forbs of the East were ill-suited to support heavy grazing. So among the few possessions carried on the 3,000-mile voyage to their new, uncertain home, each family was sure to have at least one earthenware pot containing an assortment of precious seeds from the last haying in Europe.
Even today, the great majority of American grasses used as domestic animal forage and lawn turf, such as tall fescue, smooth bromegrass and Kentucky bluegrass, are introductions from Europe, Asia and Africa. (Kentucky bluegrass is neither a blue grass nor native to Kentucky.)
Mixed in with the relatively large grass seeds – intentionally or not – were a great number of minute white clover (Trifolium repens) seeds, which found the temperate climate of New England much to their liking. In fact, the clover was one of the first forage plants to form dense pastures once the settlers had cleared patches of forest for agriculture.
Emily Dickenson’s clover, and the hundreds of small, white clover heads likely dotting your front lawn, are descendants of those early European immigrants.
The varieties of white clover can be grouped into three size categories: small, intermediate and large. The two smaller sizes, referred to as Dutch or common white clover, are the forms most often seen in today’s lawns. The Ladino version is twice as large and is commonly planted and mixed with grasses, as livestock forage.
Pluck a clover. Note the characteristic white chevron on each leaflet and slowly spin the white flower by its stem. A hand lens helps to see that it’s not a flower at all but a cluster of 40 or so miniature flowers (or florets), each one consisting of five elongate petals encasing male and female reproductive structures. And each little flower produces a miniature pod with three to four seeds. So we’re talking tiny here; 700,000 seeds to a pound.
But the reason you see such dense patches of clover scattered across the lawn has less to do with its seeding and more with its vegetative growth. Each healthy plant sends out a circlet of creeping, horizontal stems called stolons. Here and there, a stolon pauses to send down a few roots and raise a vertical shoot.
But is it a weed? Yes, if your idea of a lawn is a continuous expanse of closely mown grass. On the other hand, up until a few decades ago, most lawns intentionally were seeded with clover. As members of the pea family, clovers are legumes whose roots contain tiny bumps (nodules) packed with zillions of bacteria that can turn unusable nitrogen gas into forms that enrich the soil, a real boon to establishing a green cover in less than ideal conditions.
Then, too, at about one clover in 5,000, T. repens is the most likely of the clovers to experience that lucky set of mutations that songs have been written about.
Ken Baker is a scientist and a retired biology professor. If you have a natural history topic you’d like the author to consider for an upcoming column, email your idea to firstname.lastname@example.org.