It has long been known that the character of soil may be told, to a considerable degree, by the kind of weeds that grow on it. An old English writer pointed this out in his quaint way some 200 years ago:
"Ground which, though it bear not any extraordinary abundance of grass yet will load itself with strong and lusty weeds, as Hemlocks, Docks, Nettles and such like, is undoubtedly a most rich and fruitful ground for any grain whatsoever."
But, he goes on to say:
"When you see the ground covered with Heath, Broom, Bracken, Gorse and such like, they be most apparent signs of infinite great barrenness. And, of these infertile places, you shall understand, that it is the clay ground which for the most part brings forth the Moss, the Broom, the Gorse and such like."
Wherever soil is coarse and bouldery the weeds also are of a sturdy breed. In his long, delightful days among the mountains Muir[4] tells us what a brave show the thistles made in this new world of soil; how royal they looked in their purple bloom, standing up head and shoulders above the other plants, like Saul among the people.
WHAT THE DESERT PIONEERS DO FOR FUTURE GENERATIONS
Only the sturdiest kinds of shrubs and weeds, such as you see in the desert, can earn their keep in sandy soil, always thirsty, like that on the right. But the desert vegetation, dying and decaying—it is then called "humus"—not only knits the soil together but absorbs moisture and ammonia from the air and so helps grow good crops.