permanently productive, and all the depth you can get beyond three feet is desirable.  We question the desirability of planting orange trees even on a good soil overlying gravel, rocks or sand.  Roots will penetrate such material only a short distance usually.  It is almost impossible with such a leachy foundation to keep the surface soil properly moistened and enriched; You are apt to lose both water and fertilizer into the too rapid drainage.

Soils and Oranges.

I find this entire district underlaid with hardpan at various depths, from 1 to 6 feet down, and of various thicknesses.  This hardpan is more or less porous and seeps up water to some extent, but is too hard for roots to penetrate.  It is represented to me that if this hard pan is down from 4 to 5 feet it does not interfere with the growth of the orange tree or its producing.  Is 4 or 5 feet of the loam enough?

Four or five feet of good soil over a hardpan, which was somewhat porous, is likely to be satisfactory for orange planting.  There has been trouble from hardpan too near the surface and from the occurrence of a hardpan too rich in lime, which has resulted in yellow leaf and other manifestations of unthrift in the tree.  Discussion of this subject is given on page 434 of the fifth edition of our book on “California Fruits,” where we especially commend a good depth of “strong, free loam.”  This does not mean necessarily deep.  The orange likes rather a heavier soil, while a deep sandy loam is preferred by some other fruits.  If you keep the moisture supply regular and right and feed the plant with fertilizers, as may be required, the soil you mention is of sufficient depth — if it is otherwise satisfactory.

Oranges Over High Ground Water.

Does California experience show that citrus trees can be grown upon land successfully where the water-level is 6 feet from the surface; that is, where water is found at that level at all seasons and does not appear to rise higher during the rainy season?

We do not know of citrus trees in California with ground-water permanently at six feet below the surface.  If the soil should be a free loam and the capillarity therefore somewhat reduced, orange trees would probably be permanently productive.  If the soil were very heavy, capillary rise might be too energetic and saturate the soil for some distance above the water-level.  In a free soil without this danger the roots could approach the water as they find it desirable and be permanently supplied.  Orange trees are largely dependent upon a shallow root system, the chief roots generally occupying the first four feet below the surface.  From this fact we conclude that deep rooting is not necessary to the orange, although unquestionably deep rooting and deep penetration for water are desirable as allowing the tree to draw upon a much greater soil mass and therefore be less dependent upon frequent irrigations and fertilizations.