One way of pruning lavender
Pruning-
Choose plants that will perform reliably with minimal pruning. Keep any pruning you do mas simple as possible. For instance, don’t bother following traditional pruning methods for hybrid tea and floribunda roses, just cut all the stems down to 30cm (12 inches) high using shears, secateurs or even a hedge trimmer. prepare prunings for the compost heap quickly by using a shredder or spread them on the lawn and chop them up with a rotary mower witha grass ,box or use a garden vacuum tthat mulches too.
Further information:
How to prune your plants- Gardeners’ World
Pruning Tips and Techniques
Source: ‘Short Cuts to Great Gardens’ (Reader’s Digest 1999)
Old School Gardener
Old School Garden 
I’ve always been told that putting rose trimmings in the compost heap is a big no-no as they are so susceptible to disease, it would be easy for problems to be introduced to the following year’s plants.
Same is said of tomato plants, that disease can be passed on in subsequent years. Of course around here (California Bay Area) you have to sneak such “green waste” into the normal trash, lest the “Landfill Police” send you a nasty letter. (Landfill Police=Big Green Meanies, LoL)