overgrown, half brown rosemary bush (what made it half die and how to prevent in future)

Question

I have a large rosemary bush. Was very impressive to some. It has recently turned half dead (or brown, I assume is dead). See photo.

The side that is dead seems to be the one that is less light covered (but does get some) although also maybe slightly more sheltered from cold. Also probably slightly more harvested.

I'd like to know how to not make it die in future. I'm not sure if this is from over/mis harvesting (see para A) or from cold (see para B). Or just random vagaries of nature.

A. I left it alone for years, but for the last year, I have been very aggressively harvesting the leaves (started cooking at home, use a lot of it). I don't just take like the last part of the branch, but in addition to that I sort of strip the leaves off the woody part (since I don't want the wood, do want the leaves). Note that there are still some leaves on the "dead" part. It's not 100% denuded. And I was aggressive towards a lot of the plant, not just that side. But maybe a bit more on that (closer) side. Should I stop "stripping" and only cut ends of branches in future?

B. I live near the 7a/7b border in the USA and we did have some extended cold this past JAN/FEB. That said, it seemed to do fine for several years prior. It would be hard to bring indoors but is technically feasible (in very large/heavy pot).

Edit: I already cut pruned the dead part. Don't need any advice there. Just cause of calamity and advice on future prevention.

Answer 1

In my personal experience, (at least in my climate, [zone 4/5] where I can't leave them out all year) rosemary plants eventually just die, either from old age or difficult to determine other reasons. As such, I make a habit of starting new plants from cuttings on a regular basis, so I have some to replace the ones that die off, and also to give away if they are not required for replacements.

It usually seems to happen to old plants that have not been repotted in quite some time, since I can't keep giving them larger pots forever, but I can't say for sure that's why they die. One will be fine for years in its terminal pot, then rapidly decline and expire completely. Does not appear to be disease or pests, as other plants nearby are unaffected. Here, planted in the ground or left outside in pots they die over winter. So if you had colder weather than you did in the past, that may well have damaged it. My utility bill indicates that we certainly had much colder (and sustained cold) weather in Jan/Feb than we've had in years at this location.

I would advise rooting some cuttings while you still have a plant to get cuttings from. Perhaps it will recover; if not, you have options, then. And when you have more plants, you can harvest less aggressively to get the same amount of rosemary, without overharvesting one plant.