It looks like purple basil.

I haven't seen basil with that corrugated leaf before, but the colour and the leaf clustering do indeed suggest basil.

I too have fallen victim to the "where is that plant marker? Oh well, surely I will remember what variety of lettuce this one is..." :-)

There is a variety of basil called Purple Ruffles.Thats it. You should be able to tell by tasting or smelling it. Although I don't think it is as strong as some of the others.

It looks like the Japanese herb Shiso, aka Perilla.

Jim

I also think it's perilla. I have some purple ruffles basil. My purple basil is darker in color and the leaves are shaped the curled a little differently.

Ania

I second (third?) the ID of perilla/Shiso (and I think one last name for it is purple beefsteak plant). I remember it self-seeding like crazy, but easy enough to spot when weeding that I cleared out my unwanted ones within a season. Cheers!

Sunni

Thank you, Thank you! I knew it was not basil (guess I should have said that from the start). It is Shiso, Thank you everyone for your help. I will now mark it so that I know and will spend lots of time pulling it up from my garden paths and everywhere else it seems to want to grow (ha ha)

Mary