How long does it take for lavender flowers to come out?

Planting in April or May is ideal (so, now!) And they take about 10-14 days for the seeds to germinate. Good luck!!

SO MANY varieties of lavender. The best plants I found, after many cheap failures, came from a nursery. The people who work there should be well informed on this particular plant. If they have little or no info for you, find another nursery. I have two varieties of lavender in my Massachusetts garden. (someone removed the garden id tags) They were planted & never been moved. They do not take to replanting well & usually suffer greatly, then die. I strongly suggest that you plant lavender above ground level (a raised bed), where they can spread out & gently droop over the edges. In the Spring, when they recover & show new growth, I cut off the obvious dead branches. I do not bother them again until the flower stalks are in full bloom. Cut the stalks in early morning, tie together in clusters, & hang in a cool, dark., uncrowded place to dry. In a few weeks you have beautiful, fragrant bouquets. Look up lavender on line for more info. Enjoy for many years to come!

Are you planting plants from the nursery? Or from seeds you grew? If they have been indoors, wait until the frost is gone. Then harden them off. You do not want to lose your lavender to shock. One usually harvests lavender before the blossoms open. Here is a good guide-http://gardenmentors.com/garden-help/eat-drink-preserve/pruning-lavender-drying-the-harvest/

Also- cover your lavender in mulch or a cloche or a cold frame for the winter.