I prune back my lavendar plants in the spring, and they do fine. I read an article quoting a professional lavendar grower who suggested that they benefit from heartless pruning. Don't take them down to the ground, but taking the oldest stems out should be fine and rejuvinate the plant.

just curious if you did prune yours back and did it help?
it has been my understanding that yearly or bi yearly hard pruning prevents woody non blooming stems.... (which i have always done with mine) but that 5 years is probably way too late. is yours responding?

Sue
"The one thing all gardeners share in common is a belief in tomorrow"