Answer: This would be late winter to very early spring, before the buds begin to swell and well before they begin to grow for the season. It is related more closely to your snow cover and frost dates than your zone, but I would guess it would be some time in March for you. I usually do mine once the most bitter weather is over and spring seems to be coming, on one of those first days when the temperatures are over 40. I hope this helps.
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