After enduring chiggers, ticks and mosquitoes all summer, fall promises outdoor activities free of itchy and painful natural nuisances. We outdoor lovers look forward to walking through forests and fields without any nasty critters jumping on us.
Every fall, we stroll confidently in comfort until we feel a maddening itch at the ankle and find that Spanish needles have penetrated our sock, or a cocklebur has wedged into the top of our boot - and that our shoelaces, pants and jackets are plastered with beggar lice.
Why, as Oscar Wilde once asked, is nature so uncomfortable? Why does every autumn outdoor excursion have to include removing seeds from fabric?
Despite their annoying qualities, these 'natural attachments' make the outdoor world a much more interesting place. Try to keep that in mind the next time you are scraping beggar lice off your pants with a butter knife or a pocket comb.Plants have fascinating seed-dispersal methods. Most of them exploit wind, water and animals to spread and perpetuate their species. The success of these plants, in turn, contributes to the survival of many animal species that depend on them for food or shelter, and ultimately, to the integrity of ecosystems.
Jewelweed and witch-hazel, both common Missouri plants, have explosive seed capsules that discharge and propel seeds many feet. Hundreds of species in the composite or aster family, such as blazing stars and dandelions, have parachutes attached to their seeds that are carried aloft by wind. Fleshy fruit, such as permissions and wild plums, surrounds seeds and attracts birds and other animals, which then disperse them through their digestive systems. Plants like overcup oak have a corky layer inside the acorn that allows it to float down waterways to colonize new locations.
And then there are the annoying sticky seeds of, for example, plants in the genus Desmodium (known as beggar lice, sticktights, tick trefoil or tick clover) and the genus Bidens (called Spanish needles or beggar's ticks). These rely on furry animals to carry their seeds away from the parent plant to drop elsewhere and potentially germinate in other areas.
Such "seeds" (technically dry fruits encasing seeds) have ingeniously designed hairs, spines, barbs and Velcro-like hooks on their surfaces that cling to fur or clothing. The fruit's point of attachment to the parent plant is loose enough that it can easily attach to the coat or fur of any warm-blooded body that passes.
As mammals travel, the fruits eventually fall off or are freed from fur when animals groom themselves. If the fruits land in suitable spots, the seeds inside germinate, and a new plant generation grows and produces a new crop of aggravating, sticky fruits.
Humans, however, aren't so helpful in transporting such fruits to ideal growing grounds. When we groom ourselves after a hike, these fruits usually wind up in linty piles in parking lots or in a trash can by the washing machine.
I know of one instance, however, when this method of seed dispersal did potentially favor a plant species. In September 2001, I was with a group of biologists exploring a rare Missouri sand prairie. At lunch, we discovered that we had inadvertently collected a good number of fruits of an imperiled species of sticktight, Desmodium strictum, on our pants. Alarmed that we had unwittingly carted off a large portion of the species' seed crop, we picked them off our clothes and collected them in an empty French fry envelope, to be later broadcast over the sand prairie by one of the biologists.
If you don't want to serve as a vehicle for seed dispersal, there are a few precautions you can take. Try wearing sturdy nylon fabric, to which many seeds can not adhere. You might invest in a pair of gaiters made of heavy duty nylon that you can slip over your pants and the tops of your shoes. These will keep your socks, shoelaces and lower pant legs seed-free. Corduroy garments seem to attract fewer sticky seeds than denim. Fleece jackets and pullovers are like sticktight magnets. You'll be digging them out of your outerwear all fall and winter. Pocket combs and butter knives are helpful in scraping seeds off clothing.
Could an outing be complete without getting our hats or jackets hung up on thorny catbrier vines, or pulling blackberry or dewberry brambles from our pant legs? Thorns, spines and prickles - the defense system of many plants - deter many animals from eating plants, but they also benefit many animals. In "The Book of Forest and Thicket," John Eastman writes that vines in the genus Smilax - known by such colorful names as greenbrier, catbrier, blasphemy vine and tramps' troubles - are like "flexible rolls of vegetative barbed-wire." A thicket of greenbrier or blackberry can be impenetrable to humans and other large animals, but to small animals like rabbits, it serves as a fortress.
Thorny shrubs and small trees like hawthorn also provide relatively secure nesting sites for many birds. Research published in the December 1999 issue of Conservation Biology asserts that the prevalence of non-native shrubs like bush honeysuckle is linked to the decline of many songbird populations. Nests built in thornless species of shrubs and small trees were found to lose more eggs to raccoons and other predators, partly because of the lack of protective thorns.
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