Contact growers as early as possible. Christmas trees remain in an optimum selling size range for quite a few years. Growers generally plan to harvest only enough trees each year to meet their known or confirmed sales demand. It is rare that surplus harvested high quality trees are available for delivery in the late fall.
If possible, make arrangements to visit growers at their farms during the summer and early fall. Conversations had in the presence of the actual trees to be harvested can greatly enhance the development of a common and shared perspective on important aesthetic attributes.