| "Dwarfed Plants, They Are Normal In All But Size" by Albert A. Hansen (1930), the seven paragraph article contains these two paragraphs:
"The principle of dwarfing plants by a starvation process has been utilized in China and Japan in the production of the famous oriental pigmy trees. The process, termed Tsukurimono by the Japanese, is perfectly simple, consisting merely of continual pruning of the root systems of young trees combined with light cutting of the branches to induce more compact foliage and to prevent the loss of too much moisture. By this method a cedar tree three hundred and fifty years old was produced that is barely a foot in height. These tiny "trees of life" are exceedingly popular in China and Japan and they created a sensation when first introduced into Europe and America. Occasionally the wily oriental pigmy gardener gives his young dwarfs an aged appearance by covering them with a sugar solution and allowing ants to attack the sweet coating. They eat into the bark and the juvenile plants taken on the weather-beaten appearance of hoary old age.
"The seeds produced by aged trees artificially stunted will not produce dwarfs in turn. However, the dwarfing characteristic can be perpetuated artificially by vegatative propagation. The bark of a limb is slit a number of times and soil bound around the injured part. If the soil is kept moist, roots will appear and the cutting can be made by this means that will develop into a dwarf offspring." I
1 Hansen, Albert A. "Dwarfed Plants, They Are Normal
In All But Size," Nature Magazine, August, 1930, pp. 121, 130.
We've also discovered the following:
Hansen, Albert A. "Natural Dwarfing" in The Journal of Heredity (Washington, D.C.: American Genetic Association), Vol VIII, No. 4, April 1917, pg. 160:
"WHEN plants grow in poor soil, where they do not get enough food, they are likely to be dwarfed. Some writers call this dwarfing "nanism;" others reserve that name for the rarer form of dwarfing which is apparently due to some abnormality in the mechanism of heredity, and which is exemplified by Oenothera nanella, a dwarf mutation from Lamarck's Evening Primrose. This dwarf comes true to seed, as do most other mutant dwarfs.
"Most of the dwarf plants found in nature, however, are small only because of lack of nourishment. An example is the mesquite (Prosopis juliflora) of the southwestern States, which is famed as an indicator of sources of water supply, because of the water seeking propensities of its roots. In favorable locations the mesquite is an average tree in size, but it becomes a gnarled and scraggy shrub when growing in an environment which contains insufficient food and moisture.
"The art of the oriental gardeners in producing the spectacular dwarf 'Trees of Life' is dependent upon the starvation of the entire plant. Spruces, oaks, orange, arbor-vitae and other trees have been made to bear fruit when less than two feet in height. These pygmy products formerly sold for fabulous prices, hundreds of dollars sometimes being paid for a single perfect specimen. Professor Sorauer, of Berlin, mentions a dwarf specimen of Thuja obtusa which cost $87.50, the value evidently being so placed within recent years. These dwarf trees are in great favor throughout China, where it is said every house of any pretension whatever exhibits one or more specimens. The dwarfing tendency, according to Staunton, is perpetuated when the plants are propagated vegetatively,* but conclusive experimental data upon his point do not seem to be available.
"American gardeners have duplicated the products of the Japanese and Chinese by simply starving the plants in small pots and severely pruning the root system. Frequent transplanting is necessary in order to produce the best results. The crown is kept proportionately cut back in order that the tree may not be injured by the loss of too much water in transpiration. The limiting of the soil content is perhaps the biggest factor in the production of dwarfs."
* Manual of Plant Diseases -- Sorauer. Vol. I, part II, pg. 142.