The vast changes which human efforts make in the surface of the earth have a correspondingly important effect on vegetation. Every time a tract of woods is cut down, every time a lake is drained, every time a field is plowed—whenever any alteration is made in the landscape—the vegetation is affected. Sometimes this disturbance of the natural order of things becomes a serious menace, as in the case of deforestation. The welfare of the world is bound up with the welfare of the plants.
About a hundred years ago, a certain section of forest in France was levelled. It contained Oak, Beech, and Ash. The new trees to spring up were Birch and Poplar. After thirty years they too were felled and young shoots of the same species immediately came up, with a few descendants of the original growth reappearing. It was not until the third clearing or ninety years after the original cutting that the Oaks and Beeches began to regain their lost prestige. This is a good example of the effect that human operations have on the plant world. Wholesale cuttings tend to change the chemical composition of the soil by withdrawing certain elements, thereby causing other species to flourish which do not need this material.
When it comes to plants grown in nurseries and conservatories, gardeners are often able to make almost unbelievable changes in floral and vegetable form and structure. There has been much experimentation of recent years in connection with the effect of light, both natural and artificial, on plant processes. In general, it has been established that it is just as injurious for a plant to have too much light as too little. Steady exposure to light makes for accelerated growth of tissue. Lessening light speeds up flowering and reproduction. Control over a plant’s light supply therefore means that the manipulator can produce at will either large, luxuriantly foliaged plants which flower late, or from the same seed develop small specimens blooming exceptionally early.
Man is not content with merely controlling the external conditions which affect vegetation but often steps into their internal processes and moulds their life-forces at their very fountainhead. By the simple methods of selection and cross-breeding, he is able to work miracles with the laws of heredity, and bridge in a few years gaps which a plant would have taken centuries to span by ordinary evolutionary processes.
Luther Burbank is the modern garden wizard who has attained the greatest distinction in this field. He says: “There is no barrier to obtaining fruits of any size, form or flavour desired, and none to producing plants and flowers of any form, colour or fragrance; all that is needed is a knowledge to guide our efforts in the right direction, undeviating patience and cultivated eyes to detect variations of value.”
Burbank has many times shown that he has the knowledge, patience and cultivated eye in a superlative degree. He claims to only apply old methods in a new way, but his results have been phenomenal. In fruits he has produced many new varieties of Apples, Pears, Peaches, Apricots, Plums, Prunes, Cherries and Quinces. His Plumcot is a delicious cross between a Plum and an Apricot. Out of the Dewberry and a Siberian Raspberry he compounded what he calls the Primus Berry. A Dewberry plus a Cuthbert Raspberry equals a Phenomenal Berry. One Lawton Blackberry and one Crystal White Blackberry make one Paradox Berry.
Among the Burbank floral creations the Shasta Daisy is notable. It combines strains from Europe, Japan, and America. A new giant Amaryllis has twelve-inch blossoms. The Tigridias is spectacular, the blue Poppies are odd and there are many extraordinary Lilies.
The substitute for Grass developed by the California naturalist thrives through the most severe drought and so is of practical economic value. His improved Walnut Trees grow to a large size in a few years and his Chestnuts bear abundant crops when they are mere bushes. Spineless Cactus is a very valuable creation.
All these results are obtained in what seems to be a very simple way, yet their successful outcome is only made possible by the mind of genius working with infinite patience over long periods of years. To select out of a group of plants a few individuals which show exceptional quality of a desirable type; to save the seed of these favoured few and make further selections among their progeny; to couple with this the cross-pollenizing of different varieties or species showing a tendency to greater variation or accentuation of characteristics—all this may seem only high grade garden practice, but only one man in two or three generations has the exceptional and sympathetic perceptive faculties which enable him to attain really striking results.
On his experimental farms near Santa Rosa, California, Luther Burbank has made many thousand distinct experiments involving a wide range of plant species. It is said that at times he has had as many as three thousand tests, calling for observations on a million plants and flowers, under way at once. Probably no similar area of the earth’s surface has grown such a variety of vegetable products or had such infinite care lavished upon it.