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ity. Among the most conspicuous roadside weeds are the greater ragweed, small ragweed, meadow sunflower, artichoke, bull thistle, dog fennel, beggar-ticks, marsh elder, fetid marigold, velvet weed, Jimson weed, cocklebur, mustard, mullein, Canada thistle, woolly thistle, squirreltail grass, wild barley, sweet clover, annual brome grass, black medic, bur clover, dodder (the last three especially common in Colorado), tumbling mustard, Russian thistle, fireweed (especially common in the West), Mexican poppy (Texas), capitate croton (Missouri to Texas), sneezeweed, and buffalo bur (common from Colorado to Texas). Sunflower and marsh elder are very frequently seen in Kansas, Nebraska, the Dakotas and Colorado. Weeds of Yards.-The weeds of yards, especially of barnyards, also vary greatly. In nearly all cases they are such as can stand considerable tramping over, or else they are weeds that are avoided by stock, because of Some injurious properties residing in the plants. In the North the most common barnyard weeds are dog fennel, barnyard grass, cheeses or small mallow, Jimson weed, dock, fetid marigold (in Iowa, Nebraska to Kansas), smartweed and dooryard knotweed. In the Southwest, buffalo bur and smartweed are common. Weeds of Lawns.—Blue grass, during the dry season, may become weedy. In the greater part of the Mississippi valley, the most common weed on lawns is the smooth crab grass which fruits so closely to the surface of the ground that the lawn mower will not catch all of the seeds. Yellow foxtail or pigeon grass is also common where the lawn is not properly cut. Chickweed is one of the most common weeds in the North. Dandelion is one of the most common weeds in lawns in the Northwest. Cat's-ear (Hypochaeris radicata) is common on the Pacific coast, in Washington and Oregon.


A great many people are ignorant of the presence of poisonous plants growing in their neighborhood. In the list given below are some of the most common species. While some of these are found more frequently than are others, it is also true that some in the list are more virulently poisonous than others. In wet places in the North, the cowbane is one of the most poisonous of weeds; the fleshy roots with a pungent odor are eaten, people mistaking them for parsnips. The hemlock of the ancients, a common plant in the West, contains a deadly poison. The seeds of Jimson weed are also poisonous. The nectar in the flowers of this weed and of Wright's datura

- Fig. 33a. California poison have caused the death of chil- ivy (Rhus diversiloba). Many dren. people poisoned by touching

In the list appended below, the plant. (U. S. Dept. Agrl.)

the more poisonous species are printed in bold face type. Anemone or wind flower, black henbane, black locust, black nightshade, blood root, bouncing bet, buckwheat, bunchflower, bulb-bearing hemlock, calycanthus, caper, celandine, choke cherry, cocklebur, common brake, common juniper, corn cockle, crimson clover, crowfoot, cursed crowfoot, cypress spurge, qarnel, elderberry, flax, flowering spurge, fly agaric, hellebore (green and false), hemp, hogwort, horse chestnut, horse-radish, horsetail, Indian hemp, Indian tobacco, Jimson weed, Kentucky coffee tree, large blue flag, larkspurs, lepiota, lily of the valley, lima bean, mandrake, marsh marigold, monkshood, moonseed, mustard, needle grass, opium, Osage orange, partridge pea,' pasque flower, peach, poison hemlock, poison ivy, pokeweed, prickly poppy, purple foxglove, purple Jimson weed, ragweed, rattlebox, rose, sleepy grass, smartweed, sneezeweed, sorghum, spotted spurge, spreading dogbane, stemless loco weed, stinging nettle, stonecrop, swamp camas, sweet clover, tansy, some toadstools, tobacco, tree of heaven, water hemlock, water parsnip, white snakeroot, wild barley, wild black cherry, wild indigo, wild oats, wormseed, Wright's datura, yellow lady's slipper, yew.


Fig. 33b. Poison ivy (Rhus Toxicodendron), common in eastern North America. Many people are sensitive to its poison.



In the table which follows the most troublesome weeds of North America have been given. No doubt there are many other plants which should be classified as weeds, but it is difficult to always draw a sharp line; moreover, it is a difficult matter sometimes to determine the worst weeds for a given locality and even more difficult to determine the worst weeds for the entire country. A weed may be very bad in Iowa and yet comparatively harmless in Missouri, Arkansas, and Florida. For instance, the sow thistle is certainly a very bad and aggressive weed in the Canadian Northwest and on the borders of North Dakota and Minnesota; the orange hawkweed is a troublesome weed in the New England states and New York, the same is true of the ox-eye daisy, but it is not troublesome in Iowa, Nebraska, Kansas, or Missouri. Quack grass is an extremely troubleSome weed from the New England states to Minnesota and is becoming troublesome in northern Iowa. Some years ago Dr. Byron D. Halsted published a paper giving a scale of points of our worst weeds.1 The report was based upon reports received from more than one hundred replies from different parts of the United States. It was found that the following weeds were reported the most frequently: Canada thistle Io times, pigweed Io times, purslane I4 times, cocklebur six times, and so on. That is to say the correspondents mentioned these as the worst weeds in their particular locality. Dr. Halsted considers the following as important in

1 Proc. Soc. Prom. Agri. Sci., 1889:43.

determining the scale of points: I, the recognition of the seed; 2, separation of the seed; 3, recognition of plant; 4, prevalence; 5, robbing soil; 6, seeding capacity; 7, dissemination; 8, vitality of seed; 9, longevity; Io, root and stem propagation; I I, obnoxious qualities; I2, forage value; 13, resist eradication; I4, aggressiveness; I5, harbor fungi; 16, harbor insects; 17, soil habitat; 18, climate habitat; 19 and 20, miscellaneous. Dr. Halsted gives a tabulated scale showing the characters of the worst weeds of the country as follows:

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For the state of Iowa the weeds given in the Iowa Weed Law are the most injurious with the possible exception of the squirrel-tail; they are as follows: Quack grass, Canada thistle, cocklebur, wild mustard, sour or

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