Amer. Soc. Hort. Sci. Proc. 19: 194-200. 1922.
Fruit bud formation in Rubus and Ribes.
L. H. MacDaniels,
Cornell University, Ithaca, NY

THE fruiting habit and the time of fruit bud formation of the apple, the pear, the peach and the cherry, have been studied more or less intensively in different parts of the country by a number of investigators so that at present they are reasonably well understood. With the exception of the work of E. S. Goff at the Wisconsin Station, however, the bramble fruits and the currants and gooseberries have received little attention in this regard. The present study was begun in the summer of 1914 and carried on during the next three summers with the purpose of finding out more definitely the time of fruit bud formation and the nature of the buds on the different parts of the blackberry and raspberry canes.

The procedure was along two lines, namely that of bud examination and pruning. In the bud examination, buds were collected at different intervals and examined by dissection under it binocular microscope. The dissection method made possible the examination of a large number of buds and, where differentiation of flowers was well under way, was entirely satisfactory. The magnification (about 15 to 20) was not sufficient to determine the differentiation of the growing point in the very early stages. In the pruning work, during one season different proportions of the rubus canes were cut off and the results noted, and during another, the canes were pruned to different numbers of  buds.

BUD EXAMINATION.

Black Raspberry, var. Cumberland

Date Condition
July 20, 1914 Growing points not differentiated.
Aug. 16, 1915 No visible differentiation.
Sept. 16, 1915 No visible differentiation.
Oct. 6, 1915 Apparently the beginning of differentiation.
Jan. 11, 1915 Flowers well differentiated but zones not.
Feb. 20, 1915 Flowers differentiated about as in previous collection. Terminal flower the largest.
Mar. 3, 1917 No observable difference from February collection.

From this series of collections, it appeared that the flowers differentiated in the late fall, probably during early October.

Red Raspberry

Date of
Collection
Variety Condition
July 20, 1914 Marlboro } No differentiation of growing point into flowers.
    Cuthbert
July 31, 1914 Cuthbert Same as above.
Aug. 16, 1915 Herbert Same as above.
Sept. 16, 1915 Same as above.
Oct. 6, 1915 No apparent differentiation.
Jan. 11, 1916 Growing point only partially differentiated. Flowers not clearly formed.
Mar. 3, 1917 Flowers differentiated, but very small—much smaller than with the black raspberry at the same season.

Indications were that flowers were only very imperfectly differentiated in fall in the red raspberry, being much behind the black raspberry in this regard. Collections of the Golden Queen raspberry made August. 16, September 16, October 6, January 11 and February 20, showed no certain differentiation of the flowers. The condition was in every case about as in the Herbert red raspberry. Buds of the winter collections were large and well formed, but dissection revealed no well formed flowers.

Collections of the Columbian purple cane raspberry made October 6 showed no well defined differentiation of buds. January 11 and February 20. collections showed probable beginnings of differentiation. Collection of April 4 before buds opened showed flowers well formed in both axillary and superposed buds. The development of the flowers of the purple cane raspberry was more nearly like that of the red raspberry than the black.

Blackberry

Date Variety Condition
July 31, 1914 Eldorado No differentiation.
Aug. 16, 1915 Snyder Leaves only differentiated with certainty. Possibly the beginning of one terminal flower.
Sept. 16, 1915 Flowers clearly developed.
Oct. 15, 1915 Flowers clearly developed. Receptacle of terminal flower corrugated with young pistils.
Jan. 11, 1916 Flowers well developed—only very slightly larger than October collection.
Feb. 20, 1916 Same as January collection.
Mar. 3, 1917 No change from February collection.

It is quite clear that the flowers of the Snyder blackberry differentiate about the last of August. There is little change taking place between September and March.

Herbert Raspberry   Snyder Blackberry
 

Houghton Gooseberry

Date Condition
Aug. 16, 1915 Growing point just beginning to differentiate into flowers. No floral parts visible.
Sept. 16, 1915 Small flowers clearly differentiated.
Oct. 6, 1915 Floral parts showing, but small.
Jan. 11, 1915 Floral parts clear, stamens with anthers.
Feb. 20, 1916 Same as January collection.

The same collections were made and examined with the variety Columbus, which showed later development by about ten (lays or two weeks. The growing points of the gooseberry differentiated into flowers about the first week of August. With the gooseberry, bud examination is somewhat unsatisfactory since about half of the buds are leaf buds and would never develop flowers.

Cherry Red Currant

Date Condition
Aug. 16, 1915 Growing points differentiated into flower clusters, but no flower parts developed.
Sept. 16, 1915 Flower clusters well developed. Flower parts beginning to form.
Oct. 6, 1915 FloraI Parts showing, but small.
Jan. 11, 1916 Sepals, petals and stamens visible, beginnings of a pistil.
Feb. 20, 1916 Same as January collection.

Indications are that flowers differentiate about the last of July, or the first of August.