Cut them all the way down to just a few inches in late winter or early spring. They should grow back nice and bushy if they are healthy. And if not at least they will be easier to remove. -Ais.

I agree with Ais. If you have to replace, Salvia greggii makes a nice hedge in sun and partial sun that will stay around 2-3 feet high, flower, attract hummingbirds, and require little fertilizer, no pesticides.

Thanks for replies! I thought Salvia greggii was flowers didn't know it was shrub

Basicly, it's a woody perennial - not really big enough to be a shrub (3-4' max.), but it doesn't die to the ground in winter. You can keep it trimmed to the height you want, although too frequent trimming will lose you flowers. Reasonably frequent pruning/trimming helps keep it fairly tight - it can be a bit sprawl-y if left alone. At least, that's what I was told I it was when given a plant a few years ago; the 'bush' grows and flowers well, in a bright red, though it isn't especially tight, but it does get morning shade and afternoon sun. In full sun or with morning sun, it may be a bit tighter. And it needs with good drainage, so isn't the plant for that wet spot at the bottom of the hill...., nor the area where the run-off from the roof or gutters goes.