The peaches of New York

by U. P. Hedrick

After the fruits, the leaves offer the best means of determining groups and varieties of peaches. Leaves are variable, it is true, but usually within limits quite easily set, since the conditions causing the variations are easily discovered. The most usual ones are extremes in soil, moisture, light, heat and the age of the wood upon which the leaves are borne. Much care has been taken to illustrate as accurately as possible the leaves of the varieties given color-plates in this text, size and form being reproduced exactly and color as nearly as color-plate printing permits.

Leaf-size and leaf-form are the first characters of the foliage to study in determining varieties. The former varies somewhat in accordance with the conditions named in the foregoing paragraph but the shape of the leaf changes but little. Fortunately for the student of varieties, leaves differ most in relative length and breadth so that the shape may be accurately indicated by figures which are used in most of the descriptions in The Peaches of New York. Comparisons of the bases and the apices of leaves of different varieties often show distinguishing marks.

The color of leaves in varieties is very constant for both surfaces. The color of the foliage gives an aspect to peaches whereby a variety may often be distinguished in its summer dress at considerable distance. Unfortunately, the colors of leaves in the color-plates in this book cannot be relied upon to give much help in studying this character. Autumnal tints are uniformly the same in peaches and not to be relied upon in classifying varieties.

Several other characters of the leaves must be studied by the systematic pomologist. The leaves of some varieties are thinner than those of others, hence thickness becomes a distinguishing character. Venation of leaves—size and arrangement of veins—is important. Pubescence of leaves cuts quite a figure in the descriptions of many fruits but in the peach is of minor importance because the leaves are not very hairy and the quantity and character of the pubescence is exceedingly variable. Some varieties have relatively few leaves—others many. The leaves of some varieties fall early—others relatively late.

The margins of peach-leaves offer valuable evidence in determining varieties. They may be serrate or crenate, doubly or singly divided, glandular or glandless. Both serrations and glands are best studied in the middle of the sides of leaves, those at the base or apex often being crowded or wanting.

Petioles differ in length, thickness, rigidity, pubescence and color, so that this organ is often a substantial help in identifying varieties. Some say the color of the petiole is correlated with that of the fruit, as it certainly is in such extreme sorts as Snowball and Indian Cling, but it is doubtful whether this correlation goes further than groups and even here does not always hold. Stipules offer no distinguishing marks of importance.

Much use is made in classifying peaches of the presence or absence, the size, color, shape, position and number of glands on the base of the leaf or on the leaf-stalk. These glands may be either stalked or sessile. The terms used in describing glands are easily understood and need no definition unless it be a few words in regard to the shape. Globose glands are small globes, reniform glands are kidney-shaped. In determining the form of glands examinations must be made several times in the season, the end of the summer offering the best opportunity and even then care must be taken to secure old leaves. Glands are less variable in adult trees than in trees not yet in bearing. Pomologists for a hundred years have noted the fact that peaches with glandless leaves are very susceptible to mildew. We find this to be the case on the grounds of this Station. This correlation between glandlessness and mildew may account for the fact that peaches with glandless leaves are rapidly disappearing from American peach-lists. Wickson says it has been found that peaches with glandless leaves resist leaf-curl.[163]

Gregory has made a careful study of the glands on peach-leaves.[164] We publish here the most important facts he brings out.

"In a large number of cases the glands are stable and can be safely used to aid in the identification of certain varieties. There are also varieties in which the glands are exceptionally unstable, being on the border line between the two types—reniform and globose—and having what might be termed mixed glands. These mixed glands are of two kinds: one in which the majority of the glands are reniform, with some globose intermingled; the other in which the globose form predominates. It would be quite possible, as Carriere (1867) suggests, to distinguish a third type of glands—the mixed type.

It is important that leaves should be chosen from healthy branches on bearing trees. It is also best to obtain a large number of leaves or to examine the tree carefully before making the final selection of leaves. Mature leaves are best because their glands are full-sized and correctly shaped, while on young leaves the form of the glands is usually obscure. This is particularly true of the reniform glands. On the other hand, old, partly decayed, globose glands frequently have much the appearance of reniform glands.