This handy identification guide to the plants that cause billions of dollars annually in crop loss and control measures include information on:
-The harm that weeds cause
-Benefits from weeds
-Major weed habitats
Accurate full-color illustrations and descriptive text identify the principal weeds and weed groups that invade lawns, gardens, fields. and roadsides. Range maps show distribution within the United States.
About the Author
Golden Guides first appeared in 1949 and quickly established themselves as authorities on subjects from Natural History to Science. Relaunched in 2000, Golden Guides from St. Martin's Press feature modern, new covers as part of a multi-year, million-dollar program to revise, update, and expand the complete line of guides for a new generation of students.
Read an Excerpt
By Alexander C. Martin, Jean Zallinger
St. Martin's PressCopyright © 1987 St. Martin's Press
All rights reserved.
WHAT ARE WEEDS?
Most of the plants called weeds look "weedy." They are generally unglamorous in appearance because of their tiny flowers and unattractive foliage. A few, such as Morning-glories and Blackeyed-Susans, do have showy blossoms.
The usual definition of a weed as a "plant out of place" reflects human bias. Actually, pest plants are out of place only in terms of man's purposes. In nature's scheme, they often serve useful functions, and judging by their success in wide-open competition with other plants, they are anything but out of place.
An important factor contributing to the widespread abundance of weeds is their adaptability to diverse and adverse circumstances. Horseweeds that sometimes grow ten feet tall in favorable environment can also succeed in hard, dry soil, where plants only a few inches high may produce a crop of seeds. Other weed species can thrive even in crevices of concrete. What a contrast to our pampered cultivated plants!
Another secret of the success of weeds is their effective means of reproduction. Many of them bear tremendous quantities of seeds. Some species of Pigweed commonly yield 100,000 or more seeds per plant. Furthermore, some weeds have remarkable devices for assuring widespread dispersal of their seeds. They either float in the slightest breeze by means of tiny, feathery parachutes or attach to clothing, fur, or wool by hooks, burs, or cleavers. Seeds of still others can remain dormant for many years until favorable conditions return.
In addition, some species can multiply by vegetative means as well as by seeds. Purslane, common in gardens and lawns, not only produces many seeds but also can start new plants readily from broken-off bits of stems that have dried for a week or two. Bermuda Grass rootstocks that have been cut off and dried can still regenerate. Chopping up the plant often simply multiplies it.
THE HARM WEEDS CAUSE
Weeds cost the American farmer an estimated 5 billion dollars annually. This considers both the loss in crop yield and the expense of control measures. As consumers of agricultural products, all of us share in the paying of this huge bill.
Though this loss is tremendous, it represents only a fraction of the total harm done by pest plants. Not included in this bill, for example, is the staggering amount of time, effort, and money spent in controlling lawn and garden weeds. Nor does the agricultural loss account for the discomfort, lost time, and expense experienced by millions who suffer from hay fever and other respiratory ailments, either caused or aggravated by weed pollens. Other costs that should be added include the injury or poisoning of people and livestock by thorny or toxic weeds and the unsightliness and fire hazard created by weeds along roadsides or in vacant lots. In addition, aquatic weeds choke waterways, interfere with navigation, conflict with fish, wildlife, and recreational interests, and impede malaria control. The annual cost of controlling these aquatic nuisances alone runs into the millions of dollars.
Because of the great harmfulness of weeds, many states have strict laws requiring landowners to eliminate pest species that can spread their menace elsewhere. With the population explosion making food production critically important, federal, state, and local representatives now meet in annual regional conferences to pool information and to lay plans for coordinated attacks on the common foe: weeds. Many helpful bulletins on control measures useful on particular pests are available from state experiment stations and agricultural colleges.
BENEFITS FROM WEEDS
In conflict with our purposes, weeds are harmful, but in nature, they have considerable value. One example of their value is the benefit contributed by pioneer plants that appear immediately after land is laid bare by fire, flood, axe, or plow. These plants provide a protective covering over the ground that reduces erosion. Over the seasons, they also add substantially to the organic content of the soil.
Among other values of weeds, the leaves of Wintercress, Pokeweed, and others are frequently eaten as greens. The tender underground shoots of Cattails are also used as food. Many kinds of weeds are sources of drugs, medicines, and dyes. Songbirds, gamebirds, and other kinds of wildlife depend to a very large extent on weed seeds for their existence.
Weeds have usefulness, too, as indicators of soil quality. Vigorous growths of Ragweed and Mayweed are usually found on fertile soil suitable for cultivated crops, whereas Sandbur and Povertygrass denote sterile or poor soil. An abundant stand of Sheepsorrel generally points to an acid condition that needs correcting with an application of lime.
MAJOR WEED HABITATS
Weeds can be grouped into three major habitat classifications: fields and roadsides, lawns and gardens, and marsh and aquatic areas. These divisions are arbitrary, as only a few plants are restricted totally to such habitats.
FIELD AND ROADSIDE WEEDS comprise more than two-thirds of the pest plants of the United States. These weeds are especially important economically because they affect the nation's breadbasket. In this group too are most of the weeds that produce hay-fever pollen and cause unsightly fire hazards. Because the great majority of weeds illustrated and described in this book belong in the Field and Roadside category, no separate listing of them is included here.
MARSH AND AQUATIC WEEDS occupy a habitat that varies from seasonally dry, as in temporarily flooded fields, or moist to continuously wet, as in marshes or ponds. Some of those listed below, such as Smartweeds, Barnyard Grass, Cockleburs, and Pitchforks, are also common on farmlands: Alligatorweed, Barnyard Grass, Bulrushes, Buttercups, Cattails, Cockleburs, Giant Cutgrass, Docks, Nutgrass, Pickerelweed, Pitchforks, Reed, Rushes, Smartweeds, Spatterdock, Water-chestnut, Water Crawfoot, Water-hyacinth.
LAWN AND GARDEN WEEDS thrive in man-made, well-watered, fertile sites across the nation. Many of these weeds grow close to the ground, thus escaping mowers and sometimes even the hoe. Often they are spread by the planting of lawn grass seed, soil, or fertilizer that is contaminated with weed seeds.
Lawn and Garden weeds have wide distribution in practically every state. A few of the following also occur in farmlands: Bermudagrass, Bristlegrass, Carpetweed, Cheeses, Chickweed (Common), Chickweed (Mouse-ear), Crabgrass, Dandelion, English Daisy, Galinsoga, Goosegrass, Hopclover, Knotwood, Medick, Oxalis, Pepperweed, Plantains, Purslane, Quackgrass, Scarlet Pimpernel, Shepherds-purse, Speedwell, Spurges.
PLAN OF THE BOOK
This book is intended for a wide range of readers — young and mature, country and city folk, farmers, gardeners and lawn-keepers, agronomists, nature lovers, hunters, fishers, and hay-fever victims. In short, it is for the use of anyone interested in or bothered in any way by weeds. And who isn't?
PURPOSE The book's primary purpose is to aid in weed identification, and thereby weed control. To this end, full-color pictures and supplementary text are provided for 131 genera and their species, including the most common and important kinds of weeds, together with some of lesser consequence that are conspicuous regionally or locally.
MAPS Distribution within the United States of the weed genera and some of their species is indicated approximately by range maps, on which the absence of color (white) denotes absence of the weed; blue, presence to some extent; and purple, relative abundance. In most cases, the range shown is for the weed genus, though occasionally it is for a species.
ARRANGEMENT The sequence in treatment is based upon plant-family order, with the genus the usual base of discussion, as on the next page about Cattails, genus Typha. In comments adjoining this range map, four species of Cattails are mentioned — but since they are restricted largely to wetland habitat, this group is limited to one page, whereas for comparatively widespread and abundant weeds such as Crabgrass, Digitaria, Docks, Rumex, Smartweeds Polygonum, and numerous other especially important pest plants, two-page coverage is given.
CATTAILS are often nuisances along irrigation ditches, in rice fields, reservoirs, and elsewhere. Even in duck marshes they may be objectionable because the dense stands prevent the growth of plants that supply food and cover for waterfowl and other kinds of wildlife. Cattail marshes are desirable for muskrat production, however, because these animals feed on the edible rootstocks. The leaves are valued, too, for matting, thatching, and other practical purposes. About a dozen species occur throughout the world; four are found in the U.S.
CHESS, also known as Brome, numbers upwards of 100 species. About a dozen in the U.S. deserve designation as weeds. These grasses are particularly plentiful in Pacific and Rocky Mountain states, where their growth over slopes and valleys provides valuable forage that compensates for their nuisance in cultivated areas. The weedy species are mainly annuals from Europe. One of the most familiar, called Cheat, is such a common pest in winter rye and wheat fields in the U.S. and Canada that many farmers believe some wheat kernels change into this weed.
TALL REDTOP, also called False Redtop or Purpletop, is a familiar feature of the rural South, where in late summer and fall much of the countryside is blanketed with its dark red-purple panicles. In northern states it occurs more sparingly. A tall (usually 2-4 feet) native perennial, it produces several stems that, at maturity, are somewhat sticky, ill-smelling, and unpalatable to livestock. These features help assure the plant's success as a weed. Except for its grace and for its attractive color in fallow fields, pastures, and roadsides, Tall Redtop is a definite liability.
REED, also called Cane, Feathergrass, Carrizo (in the Southwest), and other names, is a single worldwide species. Though not as well known, it is nearly as common as the Cattails. This giant grass covers many thousands of acres of poorly drained land. It grows to 12 feet or more tall, and spreads by underground rootstocks and by leafy runners, which sometimes extend 10 feet or more from the parent plant in one growing season. In summer and fall it is topped by a large grayish plume that usually produces no seeds. The plant has minor value for matting and thatching.
QUACKGRASS was first noted as a serious weed in the U.S. in 1837. It has since become well established in the Northeast and is locally plentiful in the prairie region and along the Pacific Coast. Besides being a nuisance in lawns and gardens, this pest plant invades vacant lots, fields, roadsides and many other places. It usually grows 1 to 2 feet tall, the seed head resembling slender wheat. Almost every piece of the tough, straw-colored rootstock can reproduce the plant. In addition to the introduced Common Quackgrass, a similar native species grows in the West.
WILD BARLEYS, like their cultivated cousins, have a bearded seed head. The exotic species that are common in the West have such a bushy beard that these grasses are often called Squirreltail, Foxtail, Flickertail, or Skunktail. The barbed awns of their beards can be painfully harmful to livestock and are a frequent nuisance by clinging to clothing. Sheep can be blinded or choked from them. Of the twenty-odd species of Wild Barley in temperate regions, four are regarded as serious pasture weeds in the U.S. They are annuals or perennials, generally a foot or two tall.
WILD OATS (or Wild Oat) is one of nature's especially successful products. A native of the Old World, this aggressive annual grass is now widely established on most continents. In North America, it is particularly plentiful in Pacific Coast states and western Canada. In California, the plant's growth along roadsides, in fields, and elsewhere often rivals the density and vigor of cultivated grain crops. Wild Oats generally grows 2-3 feet tall. In especially favorable conditions, the graceful panicles of long-awned spikelets may hang 6 feet above the ground.
BERMUDA GRASS, an Old World low-growing perennial, is widely established in fields, gardens, and lawns throughout warmer parts of the U.S. In many lawns it is a serious pest, but it is also used extensively as a lawn plant in the South. Bermuda Grass loses much of its green during the winter months. It cannot survive where freezing is too severe. This grass is spread not only by seeds and surface runners but also by underground scaly rootstocks, some of which are shallow, others deep. Any part of the rootstock can grow independently. Bermuda Grass tolerates flooding.
GOOSEGRASS, an annual from Asia, is our only common weedy representative of a genus of six species native to warmer parts of the Old World. It is mainly an urban weed of gardens, lawns, vacant lots, and other waste places, confined largely to the South and the Pacific Coast. Goosegrass thrives in good soils and also in packed ground, such as in paths and in some poor lawns. The elongate finger-like spikes, usually 3 to 6 in a windmill arrangement, and the flattish ascending stems are somewhat distinctive. Crowfoot Grass is another name for this plant.
GIANT CUTGRASS or Water Millet, a tall (sometimes to 13 feet), aggressive weed, covers thousands of acres of marshland in the South. It is especially abundant in old rice fields in South Carolina and Georgia, but it ranges as far northward as Maryland, Kentucky, southeastern Missouri, and Oklahoma. Added to its other liabilities is the fact that the saw-edged leaves can inflict painful cuts, making travel hazardous through dense stands. Besides growing on land it also thrives in shallow water. It spreads from stout creeping root-stalks as well as by seed.
PASPALUM, a warm-climate genus of approximately 200 species, is abundantly represented in fields and lawns throughout the South. One species is grown for forage; another is used in soil-erosion control. The few weedy species of fields and lawns include at least two that have been introduced from South America. Their distinctive circular to oval seeds (spikelets) are flat on one side and rounded or convex on the other. They are borne in rows on two, three, or more branches (racemes). Paspalums are perennials or annuals that vary in height from a few inches to four or more feet.
CRABGRASS belongs in a genus of about 60 species of tropical and temperate regions. Only two, Small Crabgrass and Large Crabgrass, are serious weeds throughout the nation. Both are annuals from Europe, and both thrive in moist rich soils of lawns, gardens, fields, ditch banks, and roadsides. They sprout from seeds in late spring or early summer and continue growing and flowering until killed by frost in the fall, creating brown or bare patches in lawns.
Small Crabgrass, usually only a couple of inches to a half-foot high, is the worst lawn pest of the two. Setting the lawn mower high is desirable because close cutting keeps this plant from being overshadowed by other grasses. Many people confuse this plant with Bermuda Grass but the latter is perennial.
Large Crabgrass, often 1 to 3 feet tall, also grows in lawns but is common in fields, gardens, and roadsides as well. Because it develops in fields after harvest, years ago it acquired the name Cropgrass. A related species is used for pasture in the tropics.
PANIC GRASS belongs to the large genus Panicum, with about 400 species in warm regions of the world. In the U.S., 160 species have been listed. They are most abundant in the Southeast. Fortunately, none are serious pests, and only three or four are classed as weeds of fields and gardens. Panic Grass seeds are generally borne on panicles, which in some species are intricately branched. The genus includes both annuals and perennials. Some are only a few inches tall, others several feet. Two species, Para Grass and Guinea Grass, are grown in the tropics for hay and forage.
BARNYARD GRASS may be ranked either undesirable or desirable, depending on where it is growing and on the point of view. In rice fields in the South and in California, this Old World annual is a scourge to growers, yet it is a valuable asset to waterfowl and to duck hunters. Rice farmers call it Water Grass. Wildlife managers usually refer to it as Wild Millet, and they sow it in duck marshes. As its name implies, it does occur in barnyards. Barnyard Grass also grows in other upland locations but is partial to sites that are seasonally flooded.
Excerpted from Weeds by Alexander C. Martin, Jean Zallinger. Copyright © 1987 St. Martin's Press. Excerpted by permission of St. Martin's Press.
All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.
Excerpts are provided by Dial-A-Book Inc. solely for the personal use of visitors to this web site.
Table of Contents
|What Are Weeds?||4|
|Definition, adaptability and capacity to reproduce|
|The Harm Weeds Cause||6|
|Cost to farmers|
|Additional losses in control of lawn and garden pests, respiratory ailments|
|Interference with waterways and outdoor recreation|
|Benefits From Weeds||8|
|The value of weeds in soil conservation|
|For food, medicine, and drugs|
|In diets of songbirds, gamebirds, and other wildlife|
|Major Weed Habitats||9|
|Fields and roadsides|
|Lawns and gardens|
|Marsh and aquatic areas|
|Plan Of The Book||10|
|Purpose, plan of presentation of material, and explanation of maps|
|Common Weeds Of The United States||11|
|145 pages of illustrations, descriptions and maps|
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