It is not the flowers which smell rather it is the leaves. Take care when cutting back, the smell is extremely difficult to remove from hands, even when scrubbed.
Agreed. The smell is only noticeable (and not a lot even then) when cutting back and we always wear cotton gloves. They, then, go straight into soapy water in the sink for a quick rinse. We do that for a lot of plants if they are known to be a possible irritant. I always work in gloves. Mainly cotton ones (I keep about six pairs handy - at £1 per pair - and they last quite a long time) and use heavy duty ones when working with prickly or sharp plants, of which we have many.
I quite like them, but you do need to keep it in check as it is an invasive weed in my opinion. I allow a couple of plants to grow only.
