This section is from "The Horticulturist, And Journal Of Rural Art And Rural Taste", by P. Barry, A. J. Downing, J. Jay Smith, Peter B. Mead, F. W. Woodward, Henry T. Williams. Also available from Amazon: Horticulturist and Journal of Rural Art and Rural Taste.
AN amateur cultivator of fruits inquires the proper thickness for mulching, remarking, "a large apple or pear will, I suppose, bear three or four inches; not so small fruits. I think half an inch is about enough for them; also for small trees. I've seen folks mulch strawberries four inches thick - enough to kill them, for the air cannot well get through it. When mulching is rather scarce, if we lay it around our young trees, as far as the rootlets extend, will not this answer pretty well, or must it be spread still further ? Would you recommend hay or straw over half an inch thick, packed close, for trees only three to seven feet high ?"
The thickness must vary greatly according to the object in view, and with various circumstances. We have been in the practice of mulching more heavily than our correspondent. For the winter protection of strawberry beds, he is correct in recommending caution against deep covering the whole surface to prevent smothering the plants. The depth may, however, vary much acoording to the nature of the material. Soft hay or oat straw quickly packs solid when drenched with wet, and an inch or two would be likely to kill the plants. Rye straw is much stiffer, and might be safely laid on more heavily. Evergreen boughs are still more rigid, and the stiffer spruces and pines, if not cut into very small branches, can scarcely ever do any injury. A winter mulching, even if quite thin, is of much service in protecting the bare surface of the earth and small plants from sharp freezing winds. Any one may satisfy himself on this point, by examining the various depths to which the ground has frozen with a bare surface and with different thicknesses of mulching, as the earth is freezing at the beginning of winter.
When a bare surface, exposed to the sweep of the winds, has been found frozen six inches down, a thin covering of grass in another place has prevented it from freezing more than an inch or two, according to observation and measurement. The mulch, in this way, retards the freezing and retards the thawing again; and thus preventing sudden transitions, affords great protection.
For the winter, mulching of half tender trees, we should not fear to apply litter copiously; as, unlike the green plants of the strawberry, they cannot be smothered. Mice are excluded by a previously clean field, and a small smooth mound previously embanked around each tree. - Ex.