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.
The leaves died, the roots followed for want of leaves; and at the present moment I can find but about one dozen microscopic specimens to illustrate the importance of quantum suff, of healthy foliage. These "grapes for the million" are pabulum Acheronates on my light soil.
As an illustration of the importance of leaves, and the action of the descending sap, I would recommend some of your querists to try a simple experiment - as follows: Select on the same vine, after the completion of the stoning process, two branches of the same summer's growth, of equal size and vigor, and each bearing an equal quantity of fruit. Remove from each, near the old wood, a ring of bark one inch in length; then remove from one branch all its leaves, and mark the result. Such an experiment would beautifully illustrate the importance of leaves, and the action of the descending sap.
After the vine has perfected its fruit and developed the buds preparatory to another year's growth, the leaves continue their functions, and the descending sap contributes to the vine a certain amount of nutritive material. This nutritive material is stored up in the roots, and is used to develop new branches and foliage during the ensuing spring. This storing up of nutritive material can be easily demonstrated by carefully removing a vine from the open ground or pot, washing the roots and planting it in sand from which all soluble matter has been removed by washing, and watering the vine with distilled water. A vine so treated will commence growing at the proper season, and continue such growth until the conserved material is exhausted. Such being the fact, leaves are useful for more purposes than perfecting the fruit and developing buds for the ensuing year.
The leaves of plants are the important operatives in the laboratory of nature, maintaining the atmosphere in a state of purity for the support of animal life. Animals, through the functions of respiration from carbonic acid gas, - and plants, through their leaves, absorb it; by some means they separate the oxygen from the carbon; the oxygen being restored to the atmosphere to support animal life, the carbon is appropriated by and changed into woody fiber, and "the so-called hydrates of carbon, sugar, starch, tartaric acid, the coloring matter of the leaves, oil, and so forth, originate under the same conditions. If there are many leaves on the vine, large quantities of oxygen are given off to the air, and so corresponding quantities of grape sugar and wood fiber are formed. Hence it follows that the foliage is needed to nourish the fruit and render it sweet".
In plants of rapid growth, the amount of carbon required is much greater than can be supplied by the roots, such plants are therefore supplied with ample foliage, in order that the materials of woody fiber may be obtained from the air. Hence, by the injudicious removal of leaves from the vine, the branches are not supplied with woody fiber, and fail to ripen. This fact is well illustrated by such vines as the Delaware and Iona. In some localities the foliage is destroyed by mildew, the wood is not perfected, and the frost of the ensuing winter destroys them.
In confirmation of the importance of the leaf in the economy of plants, Liebig correctly states that "The power of absorbing nutriment from the atmosphere with which the leaves of plants are endowed, being proportionate to the extent of their surface, every increase in the size and number of these parts is necessarily attended with an increase of nutritive power, and a consequent further development of new leaves and branches. Leaves, twigs, and branches, when completely matured, as they do not become larger, do not need food for their support. For their existence as organs they require only the means necessary for the performance of the special functions to which they are destined by nature".
In the earlier period of the growing season, the stems and leaves act as a continuous drain upon the conserved resources of the plant and the nutritive elements contained in the soil; but as soon as the leaves attain a certain state of development, their stomata absorb from the atmosphere certain nutritive principles, as well as elaborate important elements. If the extremity of a branch is removed, and its laterals continuously nipped, the efforts of the vine are directed to the early development of the remaining leaves, and to the rapid extension of branches not subjected to the stopping and nipping process. Upon the stopped branches the remaining leaves attain an unusual development, and have their functional power increased. This increased functional activity is well illustrated in an ordinary vinery where vines are subjected to close summer pruning, or in a tomato plant that has been subjected to the pinching process - the leaves becoming larger and thicker.
The development of roots is to a great extent dependent upon the number of healthy leaves, and as we remove the leaves during the growing period, so do we injure or paralyze the functions of the roots. To illustrate the dependence of the roots upon the presence of the foliage, I need but advise the skeptic to try a simple experiment - that of taking two vines of similar age and strength grown in pots; remove from one all its foliage, leave the foliage of the other uninjured, and at the expiration of two or three weeks examine the roots of both.
It is a fact recognized by all who have made the vine a careful study, that the health of a leaf has much to do with the perfect development of the bud at its axil, and that laterals if vigorous and allowed to grow, interfere with the bud's development. The experienced cultivator who wishes to produce large and perfect bunches, carefully stops the laterals upon the canes intended for next year's crop, and as soon as danger is past of the buds breaking, he removes entirely the laterals upon that portion of the cane intended for fruiting. The importance of removing the laterals is well illustrated by the experience of several writers who have found the best fruit to be produced on laterals, and who. recommend stopping the main cane and encouraging the growth of the laterals.
If a cane intended for next year's bearing is allowed to grow to an undue length, the lower leave's usually commence decaying in July or August, to the injury of the buds at their axils, and as a matter of course affect the future crop of fruit. From experience we are convinced that the laterals on that portion of a cane intended for next year's crop should be stopped at the first joints, and as early as safety will justify, entirely removed.
Before the leaves at the base or lower portion of the future fruiting cane have their functions impaired and present an unhealthy appearance, it is advisable to stop the extension of the cane by nipping the end.
Leaves exert an important influence in the nourishment, growth, and ripening of the fruits, and those situated near the fruit a greater influence than those at a distance. As the leaves situated near the base of the stem are liable to have their functions impaired by the extension of the shoot, it is good and sound practice to stop a fruit-bearing shoot at a point one joint beyond the fruit. The leaves left attain a greater size, have their functions increased, and remain green and healthy until autumn. This process of stopping prevents the possibility of the vine being encumbered by an excess of foliage, and forces the vital power of the vine in another direction - that of producing and perfectly developing canes for the next year's crop.
To prevent overcrowding of foliage, and to allow of the necessary extension of the next year's fruiting canes, they should be trained to the top of the trellis, and then right or left, as may be deemed advantageous. By this arrangement air and light will reach the fruit, and the canopy of foliage at the top of the trellis will protect the fruit from the effects of the noonday sun. If the laterals on the main canes grow too freely, they can be controlled by stopping.
Leaves deprived of light and a sufficient quantity of air can not continue the performance of their functions in a normal manner. This is admirably illustrated in a "let it run vine." If the external masses of leaves and branches are raised, the leaves near the fruit and on the canes for next year's crop will present a jaundiced look - evidence that functional activity is giving place to chemical change. When this condition of things is arrived at, the advocates of "let it run" begin in earnest; they take a huge unwieldy tool called a pruning-knife and slash away right and left; removing the lungs of the vine; expose the fruit to the scorching effects of a midsummer sun; impair functional activity, and seriously injure the roots of the vine.
In our practice, summer pruning the vine consists in pinching or stopping. During the summer months, the vine - pruner should lock up his pruning - knife, and use his thumb-nail for pruning purposes. This doctrine will no doubt be ridiculed by some; but if the vine is subjected to proper winter pruning, the thumb-nail, or at most a small penknife, is all that is required for summer pruning.
As our experience in vine culture is not based upon the experience of to-day nor yesterday, but from observation beginning at an early age, we sometimes fancy that our notions might instruct some of your readers; and if you, Mr. Horticulturist," are of the opinion that our notions are worth printing, we may at our next attack of vito mania dress our symptoms in the drapery of ink. Al Fresco.