Experience at Glenn Dale showed that dried sphagnum could be shredded and used satisfactorily. Though perhaps the greatest advantage obtained in germinating seed on sphagnum is freedom from damping-off, the saving of labor is no small item. The chief danger seems to be lack of recognition of the need of keeping the surface of the sphagnum moist, to forestall development of a waterproof surface while the seedlings are still turgid. Fortunately, overwatering does no harm, and in case of doubt watering is always safe. Despite the need to watch the surface, the work of watering seedlings in sphagnum is much less than the work of watering them in soil. Under conditions that require watering of seedlings in soil twice a day, those grown in sphagnum require watering once in 2 or 3 days. Between the watering of the flats at sowing and the germination of the seed, screening or glass is placed over the flats and no water is applied. Subirrigation of sphagnum has not been satisfactory.

All these uses of sphagnum refer to the commercial dried product, sold in bales by florists' supply houses. Small quantities are prepared by rubbing, while dry, through a screen that has three meshes to the inch. Large quantities are run through a hammer mill, using a 1-inch diamond screen. When it is used in the open bench, the lower layers may be of peat or sand and the upper 2 inches of sphagnum. It is used alone in pots and in flats. In cold frames a layer 2 inches deep is usually ample.

Growing plants in sphagnum moss, in place of soil, has permitted economies of several sorts. The practice had been used occasionally for many years, but plants so grown had evoked suspicion in the minds of people receiving them, and little use was made of it for some time. Under the stress of war conditions, when dispatch of plants of cinchona, a strategic item, in great numbers by airplane was imperative, this forgotten practice was revived, slightly modified, and used extensively.

In previous years, half the cinchona plants that had been grown in soil and forwarded by surface ships to Caribbean points had died. Tests showed that plants grown entirely in shredded sphagnum, with considerable quantities adhering to the roots, would grow perfectly well when transplanted to ordinary soils. In one lot of 90,000 plants grown in sphagnum, forwarded by plane, and handled properly at the destination, the mortality was less than 2 percent. These plants were larger than those formerly shipped, but their shipping weight per plant was only one-seventh of that of plants grown in soil. Packing costs in time and labor were greatly reduced, and the plants were forwarded in pasteboard cartons rather than wooden cases.

Plants of many kinds have been grown in shredded sphagnum, in pots, entirely without soil. No plants tested have reacted unfavorably; even succulents and cacti have thrived under this treatment. Root systems developed on plants potted in sphagnum fill the pot more uniformly, with much less tendency to seek the edge of the pot than they show in soil. When plants thus grown are removed from the pots for shipment, the ball of roots remains intact; a plant may be dropped on a concrete floor and the pot be shattered without injury to the root ball.

In lining out plants grown in sphagnum, the only special care necessary is to mound the soil around the stem or to set the plants in loose soil without compacting. The roots grow into the soil readily enough, but for a brief period the ball of sphagnum may become in effect a well into which water drains if the surrounding soil is compact. In ordinary or dry weather no difficulty arises, and the precautions mentioned seem necessary only in unduly wet weather.

The use of mechanical humidification is another recent development that reduces greatly the labor and attention necessary in greenhouses.

Several different systems have been tried at various institutions; at Glenn Dale, most of the experimentation has been done with centrifugal atomizers. These are essentially a metal or plastic disk that is rotated inside a baffle plate at a high speed by an enclosed electric motor. A suitable device is provided to lift the water to the surface of the disk from a reservoir below. The water is discharged as a fine mist that drifts through the air of the propagating greenhouse. If desired, this device need be operated only during the daytime on sunny summer days. In winter, on the other hand, humidification is particularly useful at night when the humidity is lowered by the radiation from heating pipes. The humidifiers, however, may be operated continuously. Contrary to expectation, mechanical humidification causes less, rather than more, disease in the cutting bench. The rooting of many kinds of cuttings is improved; sometimes even cuttings difficult to root by any other means can be handled.