Answer: Since you have had the plant for such a long time, you must have provided it with good overall care. Perhaps something unusual happened this past winter, either an extended cold spell or extra cold snap, a gap in the winter protection allowed a draft, or the soil has become compacted and so did not drain as well as it used to. (Unfortunately I am not familiar with your local weather this past season, however as it increases in height it will be further removed from the heat stored in the earth at ground level, and thus more exposed to cold from all sides.) At the other extreme perhaps it dried out along the above ground trunk and crown, or the roots have become overly crowded and constricted, or something like that. Another possibility is that it did not have sufficient reserves to overwinter, based on how it grew last year although it doesn't seem that would be the case based on your description. Since it is July and has not begun to grow, I am so sorry but I suspect it may be dead.
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