Part 8 (1/2)

Have you ever noticed that some weeds are killed by one particular method, but that this same method may entirely fail to kill other kinds of weeds? If we wish to free our fields of weeds with the greatest ease, we must know the nature of each kind of weed and then attack it in the way in which we can most readily destroy it.

[Ill.u.s.tration: FIG. 56. PIGWEED]

The ordinary pigweed (Fig. 56) differs from many other weeds in that it lives for only one year. When winter comes, it must die. Each plant, however, bears a great number of seeds. If we can prevent the plant from bearing seed in its first year, there will not be many seeds to come up the next season. In fact, only those seeds that were too deeply buried in the soil to come up the previous spring will be left, and of these two-year-old seeds many will not germinate. During the next season some old seeds will produce plants, but the number will be very much diminished. If care be exercised to prevent the pigweed from seeding again, and the same watchfulness be continued for a few seasons, this weed will be almost entirely driven from our fields.

A plant like the pigweed, which lives only one year, is called an _annual_ and is one of the easiest weeds to destroy. Mustard, plantain, chess, dodder, c.o.c.kle, crab gra.s.s, and Jimson weed are a few of our most disagreeable annual weeds.

The best time to kill any weed is when it is very small; therefore the ground in early spring should be constantly stirred in order to kill the young weeds before they grow to be strong and hardy.

[Ill.u.s.tration: FIG. 57. WILD CARROT]

The wild carrot differs from an annual in this way: it lives throughout one whole year without producing seeds. During its first year it acc.u.mulates a quant.i.ty of nourishment in the root, then rests in the winter. Throughout the following summer it uses this nourishment rapidly to produce its flowers and seeds. Then the plant dies. Plants that live through two seasons in this way are called _biennials_. Weeds of this kind may be destroyed by _cutting the roots below the leaves_ with a grubbing-hoe or spud. A spud may be described as a chisel on a long handle (see Fig. 58). If biennials are not cut low enough they will branch out anew and make many seeds. Among the most common biennials are the thistle, moth mullein, wild carrot, wild parsnip, and burdock.

[Ill.u.s.tration: FIG. 58. A SPUD]

[Ill.u.s.tration: FIG. 59. HOUND'S TONGUE]

A third group of weeds consists of those that live for more than two years. These weeds are usually most difficult to kill. They propagate by means of running rootstocks as well as by seeds. Plants that live more than two seasons are known as _perennials_ and include, for example, many gra.s.ses, dock, Canada thistle, poison ivy, pa.s.sion flower, horse nettle, etc. There are many methods of destroying perennial weeds. They may be dug entirely out and removed. Sometimes in small areas they may be killed by crude sulphuric acid or may be starved by covering them with boards or a straw stack or in some other convenient way. A method that is very effective is to smother the weeds by a dense growth of some other plant, for example, cowpeas or buckwheat. Cowpeas are to be preferred, since they also enrich the soil by the nitrogen that the root-tubercles gather.

[Ill.u.s.tration: FIG. 60. CANADA THISTLE]

Weeds do injury in numerous ways; they shade the crop, steal its nourishment, and waste its moisture. Perhaps their only service is to make lazy people till their crops.

=EXERCISE=

You should learn to know by name the twenty worst weeds of your vicinity and to recognize their seeds. If there are any weeds you are not able to recognize, send a sample of each to your state experiment station. Make a collection, properly labeled, of weeds and weed seeds for your school.

SECTION XXI. SEED PURITY AND VITALITY

Seeds produce plants. The difference between a large and a small yield may depend upon the kind of plants we raise, and the kind of plant in turn is dependent upon the seeds that we sow.

Two things are important in the selection of seeds--purity and vitality.

Seeds should be _pure_; that is, when sown they should produce no other plant than the one that we wish to raise. They should be able to grow.

The ability of a seed to grow is termed its _vitality_. Good seed should be nearly or quite pure and should possess high vitality. The vitality of seeds is expressed as a per cent; for example, if 97 seeds out of 100 germinate, or sprout, the vitality is said to be 97. The older the seed the less is its vitality, except in a few rare instances in which seeds cannot germinate under two or three years.

Cuc.u.mber seeds may show 90 per cent vitality when they are one year old, 75 per cent when two years old, and 70 per cent when three years old--the per cent of vitality diminis.h.i.+ng with increase of years. The average length of life of the seeds of cultivated plants is short: for example, the tomato lives four years; corn, two years; the onion, two years; the radish, five years. The cuc.u.mber seed may retain life after ten years; but the seeds of this plant too lose their vitality with an increase in years.

It is important when buying seeds to test them for purity and vitality.

Dealers who are not honest often sell old seeds, although they know that seeds decrease in value with age. Sometimes, however, to cloak dishonesty they mix some new seeds with the old, or bleach old and yellow seeds in order to make them resemble fresh ones.

It is important, therefore, that all seeds bought of dealers should be thoroughly examined and tested; for if they do not grow, we not only pay for that which is useless but we are also in great danger of producing so few plants in our fields that we shall not get full use of the land, and thus we may suffer a more serious loss than merely paying for a few dead seeds. It will therefore be both interesting and profitable to learn how to test the vitality of seeds.

To test vitality plant one hundred seeds in a pot of earth or in damp sand, or place them between moist pieces of flannel, and take care to keep them moist and warm. Count those that germinate and thus determine the percentage of vitality. Germinating between flannel is much quicker than planting in earth. Care should be used to keep mice away from germinating seeds. (See Fig. 61.)

[Ill.u.s.tration: FIG. 61. A SEED-GERMINATOR Consisting of two soup plates, some sand, and a piece of cloth]