Short Cuts for the Gardener

by F. C. BRADFORD

THE RELATION of invention to necessity is proverbial. This matriarchal view implies that paternity is inconsequential. In matters pertaining to plant culture, however, where there are so many ways of doing the wrong thing, the genealogy of invention should include experience, despite its kinship to routine.

Necessity, under the guise of labor shortage and higher wages, often changes the relationship between cost of material and cost in labor. At the Plant Introduction Garden at Glenn Dale, Md., a case in point is presented by resort to "plunging" of potted plants, that is, sinking them to the top of the pot in soil, gravel, or a similar material. The practice has been known to gardeners a long time, but rarely used in greenhouses. It had been used occasionally at Glenn Dale with some plants whose culture in pots was difficult; uniformity in moisture supply was the principal end in view. Plant growth was so greatly improved by plunging and the labor involved in watering—a task for the best men available—so reduced that systematic study of the processes involved was begun. The practice was extended, as a labor-saving device, to plants of less difficult culture.

Careful study showed that the term "porous" when applied to flowerpots is an understatement. When plants were "staged"—placed on a thin layer of sand or gravel—in the usual way, the walls of the pot acted as wicks, and water passed outward through their sides faster than it passed through the soil itself. Under these conditions, many soils contract as they dry, and the ball of soil pulls away from the pot wall, leaving a channel down which subsequent waterings pour with little benefit to soil or plant. Conversely, the porosity of the pot walls permits the passage of moisture, when plants are plunged, from the plunging medium to the soil within the pot. Therefore it is possible to water the medium ratherthan the pot, thus avoiding the compacting of the topsoil, and, since the water moves inward rather than outward, also avoiding the leaching of nutrients from the soil within the pot.

The net result of these processes, in one lot of plants, was the use by plants plunged in peat of less than one-tenth the water required by staged plants, while plants plunged in sand used roughly one-fourth. In this lot the plants plunged in peat, with their small ration of water, grew significantly more than the staged plants. Salvias plunged in peat averaged one watering in 5 days through the summer. Fertilizer applied to the plunging media penetrated the pots in quantities sufficient to benefit the plants.

Carefully handled, coarse peat has proved to be a satisfactory plunging medium. The chief danger in using it is overwatering. When that occurs, its prodigious ability to hold water becomes a detriment. Restoration of the proper moisture content becomes almost impossible. Teaching proper restraint in use of water on a peat plunging medium to a man accustomed to watering staged plants is hard. For that reason, sand or washed gravel, though considerably less effective, may be the safer plunging medium. Even with them, the saving in labor is great.

Potted plants staged in autumn on an open bench in an unheated pit require considerable attention. Atmospheric moisture is dissipated rapidly during the brief periods of sunshine. Frequent watering of plants in low temperature tends to encourage root rot, particularly with deciduous and heather-like plants. Plants plunged in peat under similar conditions require little attention, an occasional application of water to the peat being enough to keep plants healthy.

The need of constant watchfulness of seed flats before, during, and shortly after germination takes most of an experienced man's time, if the sowings are at all large. Since overwatering of soil in flats is likely to be disastrous, he must water sparingly and often. He must manipulate shades even more frequently.

The use of shredded sphagnum moss as a medium for sowing seed greatly reduces the amount of time needed for proper care of seed flats. For some years before the war, most of our sowing had been done on shredded sphagnum, usually in flats. Live sphagnum had been used for sowing seed of certain plants, like azaleas and tropical plants, at various places in past years, but lack of live sphagnum had prevented wide use.