Answer: There are many different kinds of lavender, the hardier types that would survive in zone 6 would be Lavandula angustifolia varieties such as "Munstead" or "Hidcoate". These plants prefer a lean soil (not too rich) with a neutral or slightly alkaline pH and must have perfect drainage to survive the winter. If your soil is heavy, you may need to add sand and organic matter to improve the drainage, plant on a small mound or in a raised bed, or on a slight slope. The plants can be mulched with gravel to try to keep moisture from accumulating around the crown as well. Finally, they need full sun all day long to bloom their best and need to be planted far enough apart to accommodate their mature size reached later in the summer.
These plants grow almost woody like a shrub at the base and become quite broad through branching. They usually die back somewhat during the winter. In mid to late spring, trim away the winterkilled portions, and trim the plants back hard, perhaps as much as by half to encourage thicker growth to come in. After bloom, trim off the flower stems and also shear the plant lightly to encourage rebloom.
Good luck with your lavender.
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