The progress of bud development was studied in limber pines growing in the mountains of northeastern Utah. Initiation of new bud scales began in mid-June, several weeks after elongation of the current shoot had begun. Needle primordia first appeared in September and continued to form through the winter, until all were present in May. This winter activity is believed to be fostered by surface temperatures on the terminal buds considerably higher than ambient air temperatures.
Lanner, Ronald M. and Bryan, James A.
"Terminal bud formation in limber pine,"
Great Basin Naturalist: Vol. 40
, Article 18.
Available at: http://scholarsarchive.byu.edu/gbn/vol40/iss2/18