Drug roots are usually harvested in the fall or at the end of the growing season of the plant, but they may also be harvested early in the spring while still dormant. Roots collected during the growing season often shrink excessively in drying and so do not form the most desirable product. On small areas either a spade or a potato fork is a suitable tool for digging most roots; but if the area is large, labor will be saved by using a plow to turn out the roots, especially with such crops as belladonna or burdock. Most roots require thorough washing, and when the quantity is large this may be easily done if the roots are placed on a frame covered with wire mesh and water is applied by means of a garden hose.

All roots must be thoroughly dried. Large or fleshy roots are usually split or sliced, spread in thin layers on clean floors, and stirred or turned frequently. Good ventilation is essential, as several weeks usually elapse before the roots are dry enough to be stored with safety. The proper point of dryness is indicated when the roots break readily on being bent. The time of drying may be reduced to a few days by the use of artificial heat. For this purpose the walls of a well-inclosed room are fitted with racks or shelves to receive the roots, or large trays with bottoms made of slats or wire screen are suspended one above the other from the ceiling. The room is heated by a stove, and the temperature maintained between 125° and 150° F. Ventilators must be provided at the top of the room to carry away the moisture which is driven off from the roots. Ordinary fruit driers have been used successfully in drying roots on, a small scale, but special drying houses or kilns will be necessary for successfully handling crops grown on an acreage basis.

Leaves and herbs are usually harvested when the plants are in flower. Picking the leaves by hand in the field is a slow process, and time may be saved by cutting the entire plant and stripping the leaves after the plants have been brought in from the field. If the entire herb is wanted, it is preferable to top the plants, for if they are cut too close to the ground the herb will have to be picked over by hand and all the coarse stems removed. As a rule, leaves and herbs may be dried in the same manner as roots, but almost without exception they are dried without exposure to the sun, in order that the green color may be retained so far as possible.

Some flowers are gathered while scarcely open and others as soon after opening as possible, and in general they should be carefully dried in the shade to prevent discoloration. Hand picking is very laborious, and mechanical devices similar to a cranberry scoop (fig. 2) or seed stripper (fig. 3) may often be used to good advantage. A homemade picker may be constructed as follows: From a stout wooden box, about 10 inches wide, 14 inches long, and 6 inches deep, remove one end and connect the opposite remaining sides at the top with a stout strip, which will serve as a handle. Drive long, slender wire nails through an inch strip of wood at quarter-inch intervals, thus forming a "comb" the teeth of which should be about 2 inches long. This comb is fastened to the bottom of the box in such a manner that the teeth will project outward through the opening left by the removed end. On swinging this device, teeth forward, through the flowers, the heads will be snapped off by the comb and will fall into the box, from which they may be emptied into suitable containers.

Seeds are harvested as soon as most of them have ripened and before the pods or seed capsules have opened. Seedlike fruits, such as anise, coriander, fennel, and wormseed r are harvested a little before they are fully ripe, in order that they may retain a bright, fresh appearance, which adds to their market value. The machinery used for thrashing and cleaning ordinary seed crops will frequently serve a similar purpose for seeds of medicinal plants, provided the proper adjustments have been made. Most seeds must be spread out to dry and turned at intervals until thoroughly dried before they can be stored in quantity.