What whitewave says is good advice. If you do find that there is still a bit of green in the stem, prune hard and dig plenty of bonemeal in around the roots, topping up with a good mulch. If there is still no new growth by end of May then I'm afraid you'll just have to dig it up and throw it away. Don't lose heart, it happens to all gardeners from time to time.
Jersey trip, some tips please.
How do I bring this issue up with our neighbours?
