The daily routine of weeding is constant. The process teaches us a lot about the tenacity of weeds. If they don’t explode, they catch on your clothes, fly in the wind or arm themselves with thorns. In fact weeds are so good at spreading their seed that modern inventions have been designed from studying the whys and wherefores of seed dispersal. Good examples are Velcro, devised from the seed of cockle burr and the stealth bomber which mimics the seeds of an Asian climbing gourd, Alsomitra macrocarpa.
During the fall there always seems to be more weeding than the gardener can keep up with. A necessary tactic is to understand their means of procreation and attempting to put a halt to it. The yellow sorrel or oxalis will send its seeds in a showery explosion as soon as you touch it. The best method of eradication is to grab as much of the plant as possible with a clenched fist and tug till the plant is uprooted. The same tactic works for penny-cress (Thlaspi arvense), a cool season weed with tiny seeds that launch themselves as far as 16 feet.
When plants spread their seeds by flinging them away from the parent plant, it is called mechanical dispersal. Rain drops are frequent triggers, which aids germination with added moisture. Temperature can also be a factor; this is how hamamelis or witch hazel spread their seeds. The pods are made up of two compartments, each filled with one seed. The warmth of late summer pops the seed pod open, flinging the seeds far away from the mother plant. Our local impatiens, Impatiens capensis also known as touch-me-not, or jewel weed is a well-known native with small turnip shape exploding seed pods.
Prongs or hooks are another strategy, moving the plant away from the parent by riding on a passing animal. This method is known as passive mechanical dispersal. Bidens or two-pronged tick-seed is common in Virginia and readily comes to mind. Its ability to latch on is remarkable, evident with tiny, black spears that grab onto jacket, sweater, even hair. The flowers produced by this aster relative are bright yellow and fill unmown fields in late summer. That along with lavender asters and little bluestem make for an attractive wildflower meadow, yet all are capable of producing seed that can latch on.
In fact a wildflower meadow could be achieved by wearing an old ratty sweater, running through a high growth field in the fall, arms outstretched and then planting that sweater and waiting for spring. I’m just kidding of course, unless you're endlessly happy with weeding.
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