Can anyone identify this plant with long thin leaves with serrated edges and spikes of pink flowers at the tip of the stem? Is it a weed? Getting quite a few growing around my garden and not sure whether to pull them out or not.
I think it is Stachys palustris: marsh woundwort or marsh hedgenettle. It is related to wood betony or heal-all (Stachys officinalis). We have several colonies growing in the wet meadow areas along a local creek. I live in Denmark, where the plant isn't a problem, but it's regarded as a 'noxious weed' in Maine (USA). See http://www.ars-grin.gov/cgi-bin/npgs/html/taxon.pl?312174
Take a leave between two fingers and rub it - then smell your fingers. If it smells minty go and make yourself a tea or a put them into the salad.
It looks to me like a kind of Mentha. But it could be something else which it resembles. I'm not sure.
Whether you consider it a weed or not depends on you and your garden-desgin and feelings: Does this plant fit in your garden or not? Do you like it?
In a herb-garden a mentha is welcome.