This link with nice photos of different growth stages of a blueberry plant. What I find interesting is the different cold tolerances of the different stages, which as mentioned in this class, is an important consideration when predicting fruit production from our plants. For example, flower bud swell can tolerate 10-15F, while flower bud break is tolerant to about 20F, full bloom to 28F and petal fall (while fruit is developing) only 32F. This shows how vulnerable late developmental stages can be and how a cold snap late in the season could be detrimental to the fruit crop.
Note that this site talks about highbush blueberries and not our native bog blueberry, Vaccinium uliginosum, in Interior Alaska. I need to do more searching to find the critical temperatures for V. uliginosum! However, I think that these photos of bud stages and listed critical temps are helpful reminders that not all stages or parts of a plant have the same temperature tolerances. The plant is growing, developing and changing and as managers, one would need to be attentive to these changes.
