Cousins and Companions

WEEDS ARE PLANTS OUT OF PLACE

William A. Dayton

TO THE FARMER a weed is a plant out of place, especially if it is herbaceous, aggressive, and pestiferous.

The Oxford Dictionary gives as the first definition of weed: "A herbaceous plant not valued for use or beauty, growing wild and rank, and regarded as cumbering the ground or hindering the growth of superior vegetation."

To the stockman in the West, a weed is a nongrass-like range herb or what the ecologist calls a forb.

A considerable number of the plants that the farmer considers weeds actually are fair or good range forage plants, especially on ranges where, under unfavorable conditions of growth, the same aggressiveness and vitality that makes a species a pest in agricultural land clothe it with utility if it possesses palatability.

The late Dr. Adrian J. Pieters of the Department of Agriculture considered it unfair to brand with the stigma of "weed" plants so useful as, say, Kentucky bluegrass or red clover, which might be undesirable invaders of gardens. So he defined weed thus: "A plant that does more harm than good and has the habit of intruding where not wanted."

The suffix -weed is a familiar one in the English names of noxious plants as, for example, bitterweed, crazyweed,snakeweed, and sneezeweed, but it also appears as a suffix in the names of harmless herbaceous plants, such as beeweed, cudweed, duckweed, gum-weed, and ironweed.

The 1942 edition of Standardized Plant Names contains a list admittedly not exhaustive that includes 57 families of "weeds," 244 genera, and 518 species. Of these, the enormous composite (or "daisy") family easily ranks first, with 52 genera and 123 species. Grasses are second, with 26 genera and 52 species. Crucifers (or "mustards") are in third place, with 22 genera and 50 species.

Weeds can take it. As a class they are tolerant of drought, of extremes of heat and cold, of fire and high wind. They possess vigorous reproductive powers. Many have highly developed underground and persistent rootstocks, tubers, and the like. Frequently they produce fruits or seeds with prickles, barbs, or other prominences that fasten themselves to passing objects; some have wings, feathery parachutes, or similar items that greatly facilitate their distribution.

Weeds, as such, have far-reaching economic significance. In Iowa alone the amount of loss by weeds is conservatively estimated to be about 50 million dollars a year.

Some of the commonest weeds in agricultural grounds are not without economic value in their own right. For example, bigseed falseflax (Camelina sativa), horseweed (Erigeron canadensis), and wormseed (Chenopodium ambrosioides) yield commercial oils.

Black mustard (Brassica nigra) is the source of a familiar condiment. A considerable number are official drug plants, among them boneset (Eupatorium perfoliatum), gumweed (Grindelia squarrosa), the black henbane (Hyoscyamus niger), butter-and-eggs (Linaria vulgaris), hoarhound (Marrubium vulgare), and biting stonecrop or goldmoss (Sedum acre).

Some are occasionally cultivated as vegetables or for potherb greens, including Jerusalem-artichoke (Helianthus tuberosus), gardencress (Lepidium sativum), common sowthistle (Sonchus oleraceus), and common dandelion (Taraxacum officinale).

Moreover, some appear in horticultural catalogs as ornamentals : Prickle-poppies (Argemone spp.), centaureas or starthistle (Centaurea spp.), flowering spurge (Euphorbia corollata), common sunflower (Helianthus annuus), and star-of-Bethlehem (Ornithogalum spp.), for example.

Grasses are a prominent constituent of the weed population. The worst of these is a naturalized citizen, quack-grass (Agropyron repens), a poor relation of wheat. Of this egregious pest L. W. Kephart says: "With the possible exception of the Canada thistle, quackgrass is the most notorious of all weeds and probably causes a greater monetary loss than any other single species of plant."

Some native grasses, such as foxtail barley (Hordeum jubatum) and bottlebrush squirreltail (Sitanion hystrix) , with long-bearded heads, are often troublesome to livestock, the long, often minutely barbed awns working into the animals' mouths, noses, and eyes. The value of sheep's wool, too, may be diminished by these awns, as well as by the prickly fruits of such plants as evens (Geum spp.) and beggarticks (Bidens spp.).

Some weeds are of especial annoyance to particular groups, such as puncturevine (Tribulus terrestris) to the motorist, sandburs (Cenchrus spp.) to the barefoot child, and poison-ivy (Toxicodendron radicans) to the recreationist in the woods.

Some weeds pose interesting problems in land management. For example, cheatgrass brome or cheatgrass (Bromus tectorum), an introduced weedy annual grass, has heavily invaded many overgrazed areas (as in southern Idaho) in the Far West. In many places it furnishes the bulk of spring range forage, it quickly forms a ground cover on partially denuded soils, and it replaces plants that are hosts to the beet leafhopper thus being "of tremendous importance to sugar-beet, bean, and tomato growers." On the other hand, its life is short, its awns cause stock injuries, and it is a fire hazard when it is dry.

In the vegetative cover of range lands are a vast array of herbs other than grasses and grasslike plants sedges and rushes which the stockman calls weeds. These plants belong to upwards of 600 genera and 8,000 species and run the gamut from "ice-cream plants" of highest palatability, such as cowparsnip (Heracleum lanatum), to worthless pests, such as tar-weeds (Madia spp.) , and highly poisonous plants, such as waterhemlock (Cicuta spp.).

The broad vegetative types or formations in this country are tree, shrub, grass, or grasslike in character. There is no true "range weed" type unless, perhaps, it be the curious glasswort (Salicornia) incorrectly called samphire association such as occurs on the saline flats near Great Salt Lake. Rather, these "range weeds" occur in open forests such as ponderosa pine and aspen in shrub, grass, and sedge-rush associations, above timber line, in mountain meadows, associated with grasses, and the like. These "range weeds" are a highly important component of the range forage crop, especially on sheep range, and their values to watersheds and wildlife are great.

The literature on weeds and their eradication or control is extensive, particularly on individual species. Their control is, of course, intimately tied in with such factors as their life history, reproduction, location, and abundance. With annuals, control is established merely by preventing them from seeding.

Tests carried on in all parts of the country since 1944 indicate that in lawns, parks, cemeteries, meadows, and pastures where grass is the only desired vegetation, 2,4 D is superior to other herbicides for the control (and perhaps eventual eradication) of biennial and perennial weeds. The chemical may be applied as a spray or a dust. The size of the area, the nature of the terrain, and the nearness to sensitive crops determine the type of treatment and the method of applying it.

Many valuable crops are sensitive to 2,4 D. Most garden plantings, trees and ornamentals, tobacco, and cotton are injured by 2,4 D, even in small amounts. The utmost care must be used in applying the herbicide. Slight winds will carry the dust or fine spray to sensitive plants. Fumes may also affect sensitive plants some distance away. Suitable shields of canvas, oilcloth, light wood, or metal will help keep the chemicals from drifting. Spray planes can be equipped with check valves at each nozzle to eliminate dribble when pressure is shut off. Special precautions may be needed to prevent accidental discharge of the finely divided dust through minute crevices during flights to and from the area to be treated.

Generally, good pasture management will control weeds more surely and at lower cost than treatment with the herbicide. Investigations show that liberal applications of fertilizer, proper mowing, and regulated grazing will keep weeds under control. An infestation of wild garlic on a dairy pasture, however, may call for the quick work of 2,4 D, even though it injures the clover. Spray applied before the first of March is recommended.