When growing lavender you have lots of choices for varieties. Some grow better in cooler climates than others.
Both Munstead and Hidcote lavender (the two are of Lavandula angustifolia – English lavenders) are good candidates for Northern gardens. They’re easy to obtain, and they have been time tested to be hardy to zone 5
Hidcote lavender has a deeper, violet-blue color for the flowers and the flower head is more compact. The foliage is silver-gray and changes color slightly through the seasons.
Munstead flowers are somewhat ‘looser’ and lighter in color. It’s named for Munstead Woods. Another plus is that it can withstand hot summer temperatures better than other of the English lavenders.
Keep in mind that one of the biggest problems with growing lavender is too much moisture. If your soil is low and wet, try hilling and adding sand and gravel to allow for better drainage. The good news is that they don’t need – or like a rich soil.
Go out and give lavender a try for a border that butterflies and bees love or mixed in with your other flowers.