What to do with your new lavender plant...
Due to our geographical zoning of 4a or 4b, in southern Ontario and Quebec, English lavender is the hardiest to survive our winters. Even lavender rated for zone 5 will live in our climates. French lavender is best left for Europe or California where the zone is 6 and up. If you wish to leave it in a pot, it just won't last long once brought indoors for the winter. This truly is an outdoor plant.
In order for this plant to live, it must be planted in WELL DRAINED soil. The soil I have is clay, (what farm doesn't have clay??) it does wonderful in clay in full sun. The plants I had, in flooded areas in the spring, died after prolonged periods of saturation, like one or two months of constant wetness. When I was planting, there was a drought and I didn't know what the land looked like in the spring. English lavender is tough, but can only withstand so much... I have planted English lavender besides the obvious south of the house, also to the north (much more shady part) and to the east. All four sides of the house drain away from the house, leaving the lavender alive and flourishing. All around the house, once it was renovated, had soil back filled which is certainly not the best with small rocks and different kinds of dirt. But guess what? Lavender loves this the most as it drains water away faster.
The first year after planting the small, young plants, (leave 17 inches between them if you want a wall of lavender, they can grow 24 inches round), they will need to be watered. If it is very hot, giving them a shot of water every day is needed. I prefer late afternoon as the sun is not burning hot. After three weeks, as the plants get bigger, watering can be spaced every two days as needed. Don't prune anything yet, let it just grow.
Once the winter snows have covered your plants, they are protected by excellent insulation. But what happens when there is a lot of freeze/thaw cycles and not much snow? Using a roll of Geo-textile (thin, light, breathable) white material is perfect as well as evergreen branches or straw. That's three different ways to protect lavender. What NOT to do is use leaves or Styrofoam of plastic sheets as you will ROT your plant into oblivion... Remove all coverings as warmer weather approaches and risk of frost diminishes - early, mid May.
The second year. Let the plant grow and perhaps when they blossom in late June, you may see a few small lavender flowers here and there. Your bragging rights are slowly coming. After cutting the flowers off of their 6 inch spaghetti-like stems, now is the time you can cut stray branches and turn it into a tidy round ball. Untrimmed branches tend to get woody, which means it will look like a small tree branch. You don't want that, because new growth doesn't grow on woody branches. The goal is to always have soft, fresh, green growth because it is only from here that the lavender flowers grow. In September, when they bloom again, only less, you may see the odd flower. Since they are older, you can water once a week or as needed. They are not water loving plants, but Mediterranean bushes, which thrive in hot, dry weather.
The third year is when the plant really takes off. It will bloom twice, June and September and you will have two cuttings of flowers- most of the blooms will be in June. As the plant will have grown a lot, it is important to give it a good hair cut after the first flower cutting. Trim it into a tidy bush and you will have a healthy, productive plant that has the ability to last up to 15 years. Enjoy the lavender essential oil scent which will float around your yard...