If you’re growing rosemary, there will come a time when the plant is simply done, and will need to be replaced. It’s worth seeing how yours is doing now, so that you can order new plants for spring if the time has come…
If growing in the ground, expect 5-10 years before needing to replace rosemary
Providing the plants do not become waterlogged, or suffer from a particularly harsh winter, you can expect to get up to ten years growth from a rosemary bush. However, we find that here on the farm in Cornwall, ours are usually done within five or six years. We like to plant replacements in years three or four, because that way they are already a good size before we pull the old ones up a couple of years later.
Container grown rosemary will need replacing more frequently
The nature of growing in containers, the restriction around the roots and the way they so often get waterlogged and then freeze during the winter, means that container grown rosemary usually comes to an end earlier than plants that are grown directly in the ground. In years two and three, you may want to move it to a bigger pot. After that, we’d recommend checking and possibly replacing it in years three or four.
Some signs to look out for
You’ll know that the plant is in decline when you see several sprigs turning brown/black and dying off. You can prune them off altogether, but you may then see another few sprigs dying off. This is a sure sign that the plant is on its way out.
Also, if the plant is looking leggy and sparse, you can try pruning it to encourage bushier growth, but the chances are that it is coming to an end.