Alfalfa is ready to cut for seed when about half of the pods have turned brown and the seeds can be easily rubbed out. If al-lowed to develop too far, some of the earliest ripened and most valuable seeds will be lost by shattering.
Harvesting can be done as for Red Clover seed, the handling of the crop being as careful as possible to avoid shattering. For threshing, an ordinary threshing machine may be used, though a clover huller is better.
Quality of seed: The seeds are kidney-shaped and yellowish brown, about twice as long as broad. In ordinary Alfalfa their surface is shiny; in the Turkestan variety, owing to a coat of waxy substance which can be easily rubbed off, the surface is dull. The standard weight is sixty pounds to a bushel.
Impurities: Alfalfa plants are very tender when young and are easily crowded out by weeds. Running the mowing machine over the field several times during the first season not only destroys the weeds but also strengthens the young Alfalfa plants. Although in old fields the plants are generally very vigorous, they are sometimes choked out in spots by aggressive weeds. To avoid this, the seed should be as clean as possible. The weed seeds most commonly found in commercial Alfalfa are Green Foxtail, Ribgrass, Ragweed, Lamb's Quarters, Chicory, Yellow Foxtail and Smartweed. Noxious weed seeds less frequently found are Docks, Wild Mustard, Night-flowering Catchfly, Bladder Campion, False Flax and Canada Thistle.
Diseases: Alfalfa is less troubled with diseases than is Red Clover. It worst enemy is Dodder. Alfalfa Dodder, which is generally Cuscuta Epithymum Murr., is a yellowish parasite without leaves, consisting of a mass of fine threads from which are developed numerous roots called suckers. These suckers penetrate the Alfalfa stems where they absorb the food ready for the use of the host plant. The flowers are white and crowded into rounded clusters. Dodder appears at first in insignificant patches scattered throughout the field. These patches, however, steadily increase and after a few years a field may be so badly infested that the crop is ruined. The best way to avoid this pest is to secure seed absolutely free from it. Should Dodder have established itself in a field, however, the infested plants should be immediately destroyed. Mowing will only remove the Dodder on the upper parts of the Alfalfa; it will not affect that on or near the crown where it lives during the winter.