Yes, it's that time of year - the summer is over, the lavender flowers have all turned a dusty grey, so it's time to chop them back.
I did this lovely lakeside row of lavenders last week: and I took a photo halfway through, to show just how much can be safely taken off - a lot of lavender owners are very cautious about their pruning, and ask me worriedly to show them what is meant by the phrase "don't cut back into old wood", as they have been frightened by the dire warning that lavender won't grow back if you cut it too harshly.
This is absolutely true: like many conifers, if you cut them back too hard, you end up with unlovely dead wood and no new growth. However, it means that many people are too nervous to give their lavender the chop they deserve, so the plants get woodier, and leggier, until they fall over sideways and generally look a mess.
At that point, there is nothing to be done but to rip them out, dig over the bed, freshen up the soil with some home-made compost to bulk up the organic matter, and start again with new plants. Of course, if you have a shingle path near to the lavender bed, it is always worth keeping an eye out for seedlings, as lavender will seed freely, and shingle seems to be the perfect growing medium for an awful lot of garden plants - not to mention weeds! But if you see some nice healthy little lavender babies, loosen the shingle and gently ease them out: they will have extensive roots systems in and around the shingle, which really gets them off to a good start. Pot them up and keep them to one side until you have enough to replace the whole row of your old lavender plants.
To avoid having to do this replacement every few years, you need to keep cutting your lavender back hard every year, right from the beginning. Take a look at an individual stem: starting at the top, you will see the flower head, then a long square stalk, then the woody part of the plant. Look down along the woody part, see how there are sets of leaves one under the other? The trick is not to go below the lowest set of leaves: below that point is the "woody" growth that will not break into new leaves. Sometimes you will see a whole collection of tiny little leaves right down low where the stems come out of the ground: this is excellent news, as it means you have a fall-back pruning position if you should happen to go slightly too far when pruning!
As no-one has the time to cut each stalk individually, the technique is to isolate each branch of the lavender plant in turn, sweep up all the long stems into one hand, and cut across with secateurs, using the other hand. Aim to leave two or three sets of the leaves, and you have to balance this requirement with wanting to leave a fairly neat dome of cut foliage, as you will have to look it all the way through the winter.
This is one of those things which is so much easier to demonstrate than to describe!
I find it easiest to start at the outside of the clump, especially if they are fairly old, as these ones are. Cut a few "handfuls" quite low down, then gradually taper the cuts as you work your way up to the top of the clump. I don't like ending up with GI-Joe buzz-cuts on "my" lavenders, so I aim to get rounded domes: sort of "cloud pruning", really. But if you have your lavender as a hedge, then it might be appropriate to cut it with a flat top and flat sides, although when you do this, you may have to sacrifice a "correct" cut here and there, in order to remain within the outlines of your sharp edges.
Once done, dispose of the cuttings in your green waste bin, or on the bonfire - I don't even attempt to compost lavender, as they are usually very woody, and are always full of seeds! - sweep up the inevitable scattering of seeds, and there you are, all nice and tidy for the winter, and by cutting it back hard, it should grow back to the same size next year as it did this year, without getting larger and larger.
Interestingly, lavender are only "supposed" to have a life span of around five years: I used to be very friendly with Pete and Val Williams who ran The Herb Garden in Kingston Bagpuize house (now, alas, they've retired) and they astounded me with that piece of information. I thought they lived for years and years, and I am sure there is a chorus out there, right now, of readers saying "but I've had the same lavender plant for the last 20 years!", but apparently, they are short-lived plants. That's why cutting them back hard is such a good idea - quite apart from keeping them neat, it extends their lifespan by putting off the day when they start to flop open and split their stems.
So go on, get out there and get chopping!