Saxman wrote:
Jeff Layman wrote:

However, your lavenders will not thank you for being in a
north-facing site. Remember they are plants of open habit from
southern Europe - they are adapted to hot Mediterranean-climate sun
all day. Without that, they will tend to grow tall and spindly.

When should one cut back and by how much?

If you have to cut back a lot - you are too late! In general, it is best to
cut back in spring when the plants have started to grow. Lavender is pretty
tough, but if it is a metre high, and you cut back to 10 cm, it won't like
it. Back to 25 cm is better.

It is always best to have an insurance policy, too, so take some cuttings.
Lavender usually strikes very easily (there are some species that are very
difficult, but unless you are a Lavender specialist, you are unlikely to
have those), and will do so in an equal mix of compost and sand. Once you
have rooted cuttings, give some to some friends. At least that way if all
yours die, you can tap them for a cutting or two!

--
Jeff
(cut "thetape" to reply)