I don't think so. they don't feed on the roots they probably just moved in. If your worried spray off the roots with water it probably will be fine.

No, they do more good than harm (although it sure doesn't feel like that when you have to keep your trousers tucked into your socks and no kneeling or sitting with bare flesh about).

Thanks, Michael and campanula. That's what I figured since it's not like my garden doesn't have plenty of ants of its own. It was just really odd to see that they had colonized there.

Only thing may be that the could be aphid or scale farmers. And thus vector those insects...but the ants of themselves aren't harmful to the plant.