At the suggestion of the Director, with whom the idea originated, I have made a short study of apple twigs with the object of learning whether there exist, in mid-winter, any differences in composition between the new growth of those varieties of apple which are hardy and those which are non-hardy in the climate of Central and Northern Iowa.
Four varieties of twigs were studied, namely, Duchess of Oldenburg, Borovinca, Ben Davis and Boiken— the two first named being regarded as hardy and the two latter as non-hardy varieties. The twigs were taken from the trees, and the work done during January just passed. The Ben Davis twigs were from a single large tree*— the only one available— the Duchess from four large trees, the Boiken and Borovinca each from a number of nursery trees, three to five years from the graft; all were apparently well matured.
Patrick, G. E.
"A chemical study of apple twigs,"
Bulletin (Iowa Agricultural Experiment Station): Vol. 1
, Article 3.
Available at: http://lib.dr.iastate.edu/bulletin/vol1/iss4/3