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.
Common Natural Attachers
- Sensitive brier (Schrankia nuttallii, also known as S. uncinata): This native Missouri plant grows on glades, prairies and fields and along roadsides and railroads throughout most of the state. The stems are completely covered with hooked barbs. Its beautiful pink to fuchsia flowers tipped with yellow anthers bloom from May through September.
- Catbrier, greenbrier, blasphemy vine, tramps' troubles (several species of the genus Smilax; some are without spines): These native Missouri species grow in most parts of the state in forests and woodlands, and along roadsides and railroads. Dense thickets of catbrier vines, with occasional or abundant thorns or prickles, provide nesting sites for many songbird species and denning areas for small mammals. Ruffed grouse and several songbird species eat their fruits. Deer will browse thornless leaves and new shoots.
- Blackberries, raspberries and dewberries (about 16 different species in the genus Rubus): Some species grow commonly throughout most of Missouri in prairies, old fields and woodlands and along streams, roadsides and railroads. Others are restricted to specific natural communities. Thickets of blackberries, with their bristle- and prickle-covered stems and leaves, provide excellent, protective habitat for small mammals and nesting birds. The fruits, of course, are relished by many animal species.
- Hawthorns (about 50 species in the genus Crataegus, including C. mollis, our state flower, are native to Missouri): Most species are widespread in the state. Some prefer open habitats, but others prefer shaded understories. Thorny hawthorn shrubs and trees provide excellent nesting sites for many bird species. Hawthorn fruits are eaten by ruffed grouse, cedar waxwings and fox sparrows. Loggerhead shrikes (also known as butcher birds) will impale insects, small mammals and amphibians on the thorns before eating them. Sometimes these birds will not eat their skewered prey but leave it as a territorial display. Washington hawthorn (Crateagus phaenopyrum) is an attractive landscaping plant that is more resistant to cedar-apple rust than are other hawthorns.
- Tick trefoil, sticktights, beggar's ticks, tick clover (about 18 different species of the genus Desmodium are native to Missouri): Some Desmodium species are restricted to high quality, undisturbed prairies, and a few grow in wet lowland areas. Most others grow in acid soils of chert, sandstone or granite, or in rocky open woods. The species most often encountered in old fields is Desmodium paniculatum. Two common woodland and forest species are D. glutinosum and D. nudiflorum. Flat Desmodium fruits, usually occurring as a chain of several fruits, are covered with Velcro-like bristles. The fruits are eaten by wild turkey and bobwhite quail, and the leaves are browsed by deer and livestock. They are nutritious and high in protein.
- Cleavers, bedstraw (Galium aparine): Native to Missouri, it grows throughout the state in forests, woods and other shady areas. The fruits are bristled and the stems are covered in tiny, coarse hairs that adhere to clothing or fur. The stems break off easily from the plant base and cling to mammal passersby.
- Burdock (Arctium minus): Native to Europe, burdock grows throughout Missouri in disturbed areas like waste ground, woodlands, thickets and along railroads. Burdock can decrease the value of wool or other fur if its barbed fruits become entangled in it.
- Queen Anne's lace (Daucus carota): Native to Europe, Queen Anne's lace grows throughout Missouri in fields, degraded prairies, thickets, gravel bars and woodlands, and along roadsides and railroads. This is a biennial plant that blooms and produces bristled fruits in its second year of growth.
- Spanish needles (several species in the genus Bidens): Native to Missouri, this grows in moist soil wetlands, along the edges of marshes and ponds and in open and grazed woods, glades, fields and thickets. The barbed fruits seem to jump onto clothing. Mallard ducks eat the fruits and muskrats eat the plants.
- Cocklebur (several species in the genus Xanthium): Native and introduced species grow throughout Missouri along roadsides and railroads, in alluvial soil along streams, in fallow fields and around ponds. The indigestible parts of the spiny fruits can mat together in digestive systems of animals and eventually cause death.
- Hedge parsley (Torilis arvensis): Introduced from Eurasia around 1900, hedge parsley is scattered throughout most of Missouri in woodlands and recently cleared areas, on alluvial ground and gravel bars and along roadsides and railroads. Their oval, bristled fruits attach easily to clothing or fur.
- Agrimony (Agrimonia pubescens): Native to Missouri, agrimony grows throughout the state in swales in dry open or rocky woodlands, either in lowlands or uplands. A fringe or cap of bristles on the fruits enable them to adhere to fur or clothing.
- Barnyard grass (species of the genus Echinochloa): Scattered throughout the state, barnyard grass grows along roadsides and in moist ditches on moist ground along fields, pastures, streams and ponds and in waste places. Needle-like awns on the fruits can attach to clothing and fur.