A, ‘Talk on Weeds x Book SE ers Gopyright N° COPYRIGHT DEPOSIT: % bik Nyt A ‘Talk on Weeds An address delivered before the County Road School, Clinton County, Iowa, 1910, with an appendix describing a few weeds BY L. H. PAMMEL, Pi DP: PROFESSOR OF BOTANY, IOWA STATE COLLEGE AMES, IOWA va Copyright 1910 by $ « Table of Contents PAGE What is a Weed, Kinds of Weeds, Annual, Winter Annual.......... 5 Biennial, Perennial, How Weeds Spread, Vegetative Propagration... 6 Seed Propagation, Dissemination or Scattering of Plants........... i" RUC INT TRT ALAS eee pay fet ce feuint Sin int Oovicaia alates) ker sate lev esaa-e «wilde Slateliete eleva sielsivne.« 8 Explosive Properties, Seeds Burying Themselves..............-..+- 9 Menta eeu A SOM be PMPUTS-“SCCUS - acielai so Weoley) one sleldteuchalsis 48 Plantain, Buckhorn, Composite, Bull Thistle....................4.. 49 Cemade tnistic, Cockle Bur; Ragweed... 1. c.s sk eee eee be we nes 50 LESDISG Lael s teen 6 ton bad SG et oe Eee eRe: aR See ee 51 Suggestions for the Teacher................... Bt Serer iaiahe ctta state 52 RRS RA OE SMU ATU EOOTITCE Tava ciatelose:sisi oie. severe a) s'3 8 aleve 6,4 ore eluate: era o ble piste chs 53 Bibliography ........ havea We alatachiee ace tevelta Sata shee gi itittete Siete thee cere SAO A STUDY OF WEEDS IMPORTANT I am invited to address you this afternoon on the subject of weeds. I am sure you will agree with me that this is a most important subject for the farmers of Lowa and those who are in- terested in making our state beautiful. The weeds in villages, cities, along the highways and on our farms are a continual men- ace to the agriculture of this state. It is important that we be- cin to realize the menace that weeds are to our agriculture. Iowa should realize the importance of this problem and we should be- gin at once to clean up, because it is far more economical to do so now than in a decade. WHAT IS A WEED. A weed has been defined as a plant out of place. This defini- tion is concise, but is as good as any. Oats growing in a wheat field, if not wanted there, must be looked upon as a weed. A weed may also be defined as a plant detrimental to the growth of a garden or farm crop, in short detrimental to horticulture and agriculture. A great many people regard plants which have inconspicuous flowers as weeds; they exclude, of course, such plants as are cultivated for some purpose. Such people regard the inconspicuous plants of the forest as weeds, forgetting that plants like the Dutechman’s Breeches, Bloodroot and Hepatica are most useful plants in the forest and are just as much a part of it as the oak or maple. They do not, however, regard blu grass as a weed. In the forest, however, bluegrass must be reg urded as a weed. In a bluegrass pasture such plants as fox- tail, golden rod, vervain and crabgrass are weeds. They check the growth of this useful forage plant. KIND OF WEEDS. Weeds may be classified according to their duration of life into the following classes; annual, winter annual, biennial and perennial. Annual.—The annual weeds are the most numerous and are easily recognized. The seed germinates in the spring, it sends up a stem which produces flowers and seeds the same season and then dies. Foxtail, ragweed or kinghead, smartweed, crabgrass, horseweed belong to this class. A large number of our weeds belong to this class. Winter Annual.—These weeds do not differ essentially from 5. the annual. The seed germinates in the fall, a mat of leaves is produced and the next spring a stalk is sent up which produces flowers and seed, then dies. Shepherd’s purse, wild barley or squirrel tail, pepper grass in our climate, but in the south many more weeds belong to this class. Winter wheat and win- ter rye are winter annuals. Biennial._—The seeds of biennial weeds germinate in the spring, the plant produces a mat of leaves with a short stem, it passes through the winter in this way, the next season it sends up a stem on which flowers and seed are produced. This ends its existence. Burdock, Parsnip, Carrot, Mullein, and Bull Thistle are representatives of this type. These weeds are common every- where in the state. Perennial.—Th. verennial weeds are often long lived. The seed germinates, some.-mes a stalk with flowers is produced the same season. The ~lant continues to live year after year. Peren- nial weeds are the most difficult to exterminate. Weeds of this type are numerous and in Iowa are represented by Canada thistle, Morning glory, Milkweed, Quack grass, Nimble will. HOW WEEDS SPREAD. Weeds spread in two days by (1) vegetative propagation and (2) seed production. Some weeds have both methods, some only one. Vegetative Propagation —In this method of reproduction the stem or root serves to propagate the plant. This is brought about in three ways, (a) by stem above ground or wunder- Tumbleweed (Amaranthus graecizans), Scattered by the wind against a fence. (Bergen.) ‘ 6. jn nnn nnn eee yntE NSIS SSE ground. The stem may be recognized through the presence of leaves or scales. Quack grass, Germander, Northern nut grass, and Morning glory spread by stems. The Quack grass stems, called roots commonly are near the surface of the soil, some- times over three feet long, and every severed part gives rise to a new plant. (b) These plants spread by roots, sometimes they are flehsy and in other cases they are thin and slender. Dock, Horseradish, Horse nettle, Sheep sorrel and Dandelion. The Milkweed spreads horizontally in the soil and may attain a length of 14 feet. The roots of the Horse nettle on the other hand spread deeply in the soil, sometimes to a depth of three and one- half feet. These roots, when severed give rise to new plants, buds forming on these roots. (¢) The third type propagates partly by root and partly by stem. ‘The upper part of the Canada thistle is stem, bearmg minute scales Sop itl the lower root which develops buds. Seed. Propagation. —The vast majority of weeds produee seeds. The only weed in the state which has never been known to pro- duce seed is the Horse Radish. It flowers frequently but seeds are never produced. The Canada thistle blossoms freely but it does not seed abundantly. At least this is true for lowa. lt relies chiefly, therefore, on vegetative reproduction. The quack grass spreads as freely by seeds as by its underground stems. Some weeds produce an enormous number of seeds, from a few thouand to over a hundred thousand on a single plant. A single seed of Squirrel tail grass germinates, from this seed a large number of stems arise, each with a spike that contains 50 or 60 seeds, so that the progeny soon becomes greatly multi- plied. Dr. Beal estimates that a large purslane plant produces 1,250,- 000 seeds, a patch of daisy fleabane 3,000 to the square inch. We found the following number of seeds per plant, horseweed 324,000; pigweed, 115,600; Jimson weed, 89,100. Dr. Halsted found seeds in some weeds as follows: Speedwell, 186,292; Shepherd’s purse, 17,600; Pepper grass, 12,225; Charlock, 9,900. Hitcheock and Clothier record the weeds seeds as follows: Yellow foxtail, 113,600; stink grass,.180,000; cocklebur, 9,700. DISSEMINATION OR SCATTERING OF PLANTS. The scattering of plants is called dissemination and this is accomplished in the following ways: (a) wind; (b) water; (e) animals; (d) explosive properties; (e) seeds burying them- selves; (f) man as an agent. Wind.—The wind is an important agent in a large number of weeds. The dandelion may serve as an illustration. The ‘*seed’’ is cylindrical with a long beak, coming from the beak 1s are a large number of fine threads, collectively called the pap- pus. These give it a parachute-like arrangement and permit the seed to sail through the air. This weed owes its wide distribu- tion to the facilities for dissemination. Canada thistle; Bull thistle, Horseweed and many plants of the Sunflower family have similar contrivances. The 7’wmbleweed is another type of weed a—Seed of beggar-tick’s, b—Spanish needle carried by animals. (C. M. Ki ecde earried by the wind: a—golden rod, b—hblue lettuce. (C. M. King.) disseminated by the wind. The plant grows in circular form and when mature is severed from the root close to the ground. In this form it rolls over and over scattering the seed. The Rus- sian thistle is like it, but each seed is attached by a slender thread like body which becomes severed from the plant, drops the seed as it rolls over the ground. Water.—Weeds are scattered by the water in two ways (a) in a mechanical way, the seeds, plants or roots are carried by the water. I have seen fields covered with wild oats that had come from higher ground along the streams or ridges, stems of Quack grass have been scattered by the water in this way. (b) Many seeds have bladders filled with air, as in Dock. The three cornered seed is surrounded by the calyx; one or more of the lobes contain a cylindrical body called the tubercle, this is filled with air and makes the seed boyant which enables it to float down the stream and seatter the seed wherever it is lodged. The seeds of Peppergrass when moistened become mucilaginous and cling to the hoofs of animals or shoes and in this way steal a ride. Animals.—Various animals like cattle, sheep, horses, squirrels, 8. birds, ete., scatter seeds and fruits. This is done in two ways: (a) Where the fruit or seed is edible as in the black night shade, cherry, poison ivy, seed of dandelion, thistle, etce., crows scatter large numbers of seeds of the poison ivy. Millions of these poison ivy seeds are annually consumed by birds. Large num- bers of seeds of the dandelion, thistle, foxtail are consumed by birds some of these are accidentally scattered in this way. Birds are undoubtedly useful, however, in destroying large numbers of weed seed. The colored fruits usually have hard seeds so that they can pass the digestive tract of birds uninjured. (b) In the second type the seeds cling to animals. Many of our weeds have excellent contrivances for such dissemination. We will mention in this connection the cocklebur. Each cocklebur has two so-called seeds. The bur is provided with hooks tnae cling to any passing animal and I have seen them scattered for miles. The Burdock, another plant of the same family, has num- erous seeds in a head; the hooked appendages get in the hair, tails of horses, cattle, ete., where they form balls and thus the seed is scattered. The Spanish needle or boot jack of the same family has a flattened seed with two slender pointed bodies that are barbed downwardly like grappling irons; these cling to pass- ing animals and carry the seed. Another weed, the Tick Trefoil, belonging to the Pea family has a pod containing several seeds, this pod breaks up into separate pieces when ripe, each contain- ing a single seed. The pod is provided with hairs that are hooked and so clings to animals. When removed the seed has often trav- eled a long distance with the animal. Many other seeds of this family like Licorice may be mentioned. Weeds with similar contrivances are found in members of the Borage family, like Hound’s tongue, stickseed, ete. Explosive Properties—The seeds of a few weeds have explo- sive properties. The seeds of the common yellow field sorrel has a straight pod which, when mature and touched, shoots out the seed like shot from a gun. The pods of certain vetches contract and twist when mature, forcing the seed out. Contraction of capsule of the three-seeded mercury scatters the seed, throwing it some distance. This method of scattering can be observed bet- ter on such a plant as the common Castor oil bean. Seeds Burying Themselves.—A few of our weeds bury their seed, but the needle grass growing on our dry sterile hills has a sharp point to its ‘‘fruit,’’ with small hairs which point obli- quely upward. There is also a long awn to the fruit, this is sen- sitive to moisture, it contracts when dry and straightens out vhen moist and in this way buries the seed. MAN AS AN AGENT. Man is an agent in many different ways of which the follow- ing may serve as illustrations: (a) impure seeds; (b) railways; (ce) vehicles; (d) threshing machines; (e) cultivation; (f) pack- ing materials; (g) wool; (h) plants eultivated for ornamental purposes; (i) cultivated for food. Impure Seeds.—Many weed seeds are seattered with various agricultural and garden seeds. Buckhorn, dodder, wild carrot, ragweed, nimble will, bracted plantain, dock, quack grass, chic- ory, Canada thistle and many other weeds have been scattered Some of the impurities found in alfalfa: iJa—alfalfa seed, 7b—toothed bur-clover, Jc—spotted bur-clover, 2c—yellow trefoil, 2b—seed natural size, 2d—pod, 8a—sweet clover, 3b—seed natural size, }c—bracted plantain (Plan- tago aristata), 5—buckhorn (Plantago lanceolata), 6—sour dock, 7—Canada thistle, 8—dodder, 9—quack grass, 10—sheep sorrel, 11—wire grass or Canada bluegrass (Poa compressa), 12—bluegrass. (Lettered figures after Hillman.) with Agricultural seeds. One farmer in Iowa sent to me twenty different kinds of weeds found in his clover meadow which were 10. introduced with clover seed. In some cases it is difficult to separate the weed seeds from clover seed as dock, buckhorn and bracted plantain. In other cases there is no excuse for the pres- ence of these weed seeds. One can nearly always tell where the seed comes from beeause of the presence of certain weed seeds. It may be of interest to give a few statistics on the weed seeds commonly found in some of our agricultural seeds. lowa Standard Kind of Seed Purity Vitality Purity _ Vitality PLIES 3 Lue ee eons a aey 91.1 87.6 96. 80. PEG AAOWE . bit ds ake 96.6 87.8 92. 80. mine Clover ciate. oe.