"Bill who putters" wrote
"David E. Ross" wrote:

If it is indeed pennyroyal (Mentha pulegium), it requires constant
moisture. It even tolerates wet soil. It needs either full sun or part
shade and occasional feeding.

However, pennyroyal has round leaves. Your photos shows long, pointed
leaves.

Be careful with pennyroyal, both in your garden and in your mouth. All
mints can become very invasive if they escape a container. Pennyroyal
can be toxic if you eat significant amounts, but it's safe in small
amounts (e.g., as a flavoring).

Essential oil of pennyroyal once used to abort children. Still useful
to drive ants out of a home. Smells sweet then cloys . A little goes
a long way.

All true. I've grown M. pulegium before, but I think this is arvensis.
Actually its leaf form is more like the American pennyroyal, Hedeoma
pulegioides. But I wonder if the same compound that's bad is also in this,
as well as the American.
Here's what the plant normally looks like, maybe someone can confirm/deny my
ID:
http://webpages.charter.net/slyrp/Pl...20arvensis.JPG

The leaves are I guess at most 25mm long.