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Thoreau and the ‘wonders of seeds’

Milkweed plants in Jonesborough’s butterfly garden have been bursting their pods and sending aloft some first seeds. The sight calls to mind the characterization of this plant by the 19th century American naturalist, Henry Thoreau. Its manner of seed dispersal seemed most emblematic to him of nature’s ingenuity in engaging various agents–animals, water, wind–to assure continual rejuvenation, as of the significance of plants’ success in this endeavor, for us and all creatures.
An arresting description of the common milkweed appears in Thoreau’s late writings, published posthumously as “Faith in a seed.” He terms this plant “All American,” it being native to North America, as several other milkweeds are. The large seed pod, of “faery-like casket shape, somewhat like a canoe,” he notes to be covered with soft prickles and offset from the stem at various angles “like a flourish.”
A pod can contain several hundred, densely packed seeds, he observes. When these are “weaned” and mature, no longer requiring nourishment from the native plant, the pod bursts open by a seam along its convex side, often after a rain. Each seed has attached to it a downy band of extremely fine silken threads. These, Thoreau writes, fly apart when released, “opening with a spring [and raying] their relics out into a hemispherical form–a buoyant balloon which bears the seed to new and distant fields.” When the pod eventually is empty of all seeds “you may see what a delicate, smooth, white- or straw-colored lining this casket has.”
He was familiar with jimsonweed whose prickly fruit, quite resembling the common milkweed’s but round or oval shaped, can now be seen here, too. This plant has large, pleated, funnel-shaped, white and quite showy flowers.
However, unlike the milkweeds, which are host plants for a group of “milkweed butterflies” including monarch, viceroy and others, the jimsonweed’s poisonous foliage supports no native insects as host plant.
Thoreau knew it to be among the naturalized foreign introductions which botanist Asa Gray had surveyed, reaching almost 300 species in the northern US, in 1848. He acknowledged the ease with which this “veteran traveler,” like other plants “carried from one country to another” through commerce, can become a “cosmopolitan weed.” It shares with the milkweeds the characteristic of prolific seed production. On one plant I recently found 49 of the prickly pods and, cutting open one of these, counted 93 seeds. From this one jimsonweed could potentially come more than 4,500 new plants!
The weedy Johnson grass now proliferating along the waysides exemplifies seed abundance to an even greater degree, as a single mature plant can produce over 80,000 seeds and 200 feet of underground rhizomes. Such “unwanted,” exotic-invasive foreign plants, some of which known even to Thoreau, have great harm potential for Tennessee’s own, native flora and wildlife.
Nature is a “granary” for all her creatures, Thoreau concluded from long study of her fecundity in seeds and their dispersal. If you can “convince me that you have a seed,” he wrote, “I am prepared to expect wonders.”