The Undisputed Most Painful Hitchhiker
S tick-tights or beggar’s-ticks (Desmodium cuspidatum) produces slender legume fruits that break into small, one-seeded joints covered with tiny barbed hairs. Technically, this special kind of legume fruit is called a loment. The individual joints are so flat that they are exceedingly difficult to remove from your socks. Like little flat ticks, you must individually pull off each one. This can be exasperating when your socks are covered with them. Several species of this remarkable hitchhiking herb are native to the midwestern and eastern United States.
T he seeds of some parasitic mistletoes are also coated with a very sticky substance that aids in dispersal by birds. Desert mistletoe ( Phoradendron californicum ), a common parasite on cat-claw acacia ( Acacia greggii ), produces juicy, bright red berries that provide numerous birds with food and water during the winter months. If you walk along a desert wash in the Colorado Desert region of the southwestern United States, you can often spot a black bird called the phainopepla ( Phainopepla nitens ) near clumps of mistletoe. This bird is easy to identify because of the conspicuous crest on its head. Mistletoe seeds are covered with a glue-like substance that sticks to the bills of birds. When birds try to clean their bills, the seeds adhere to the limbs of other trees and shrubs. The seeds also pass through the bird’s digestive tract and are transported from one bush to another in the bird’s droppings. In fact, this probably explains the derivation of the word mistletoe: from two Germanic words: mista (dung) and tan (twig); referring to bird droppings on a branch or stem. Apparently when the word mistletoe was first used in Europe, people were already aware of the dispersal of mistletoe seeds by birds.
C ertainly one of the most painful hitchhiking plants in the southwestern United States is jumping cholla (Opuntia bigelovii). Although it only received 5 SRDUs for removal from interwoven socks, the spines are exceedingly difficult to pull out of rubber soles and elastic human skin. Like other kinds of cholla cactus, the cylindrical stem segments are densely covered with slender, barbed spines. In fact, this species is sometimes called "teddy-bear cholla" because of its dense covering of spines. What makes this cholla so unique is that the stem segments or joints break off with the slightest touch and become firmly attached to various body extremities. Unlike the unrelated but truly amazing Mexican jumping beans and California jumping galls, this cholla doesn’t really jump. If you barely touch or brush against the spines and then suddenly jerk away, the fuzzy stem fragment will be instantaneously upon you. Trying to pull out the barbed spines is not only frustrating and excruciating, but usually results in the joint or fragment becoming attached to another part of your anatomy. On a field trip to the Anza-Borrego Desert of San Diego County, several students attempted to remove a segment from a lady’s shoe, only to have it transferred to the shoes of each chivalrous male. It finally ended up on the hand of a screaming (bleeding) student who promptly flipped it full force into Mr. Wolffia’s groin region. From that day forward the Wayne’s Word staff always carries a pair of needle-nose pliers when walking through jumping cholla country.
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T he easily fragmented stem segments of jumping cholla are one of nature’s most effective methods of hitchhiking and vegetative reproduction. Thickets of jumping cholla covering entire hillsides or alluvial fans may have developed from fragmented stem segments that became rooted in the desert soil. Although jumping cholla produces flowers, the seeds of most populations are typically sterile and reproduction is accomplished without sexual reproduction (technically referred to as apomixis). You could say that jumping cholla is a master in the art of hitchhiking and cloning itself.
All of the bedstraws have sticky habits, too. Although the plants are low to the ground, the seeds do have a way of traveling far and wide by hooking a free ride. Some of the feathery goldenrods have a way of messing up things, too, but they are forgiven for their long, late display of color. So are the mums forgiven, although their seeds are better behaved.
The seeds are traveling and sticking to anything they can grab on to, either fabric or fur. Or another common seed carrier are the feathers of birds. Some seeds such as those of the Eupatorium clan are hard to avoid. The old, browned stalks of these tall, elegant plants replace the beautiful statures of the joe-pye weeds or the stately bonesets. These native plants are often used at the backs of borders for their tall finesse that they add to any scene.
This helps to explain why there are so many dandelions in the lawn come summer. Another dramatic dispersal of seed is demonstrated by the explosive nature of the witch hazel seed. The fat pods of seed form soon after the flowers appear either in late fall or early spring, depending on the particular species. When ripe, the fat seed capsule opens to explode its black seed out on the ground.
Although impatiens seeds do not stick to fabric, they provide a practical lesson in seed dispersal. No wonder they have earned the nickname ''touch me not.'' Where early frosts have not destroyed these plants, look underneath the protected leaves to see the spirally fruit. Touch it and the seeds explode. When volunteers of tiny seedlings appear in pots and borders next summer, you can recall where these seeds come from.
Another fascinating way of seed dispersal, too often overlooked, are the unusual pointed seed pods of the geranium clan. These plants are not named cranesbills without reason. The tiny seeds form at the tips of the cranelike formation and sling off, which is one reason to explain why a geranium sprouts over here, when it was planted over there.
THERE is more to fall cleanup than raking or blowing leaves away. Although such effort should have top priority to allow the green grass underneath to breathe.
In the spring, the feathery stage of the dandelion flower is nothing more than another form of seed dispersal. What is thought of as a lovely soft puff to blow is just the dandelion's way of getting around. At the base of these light parachutes is a seed. And where it lands, of course, is where the seed grows.