Help with plant ID

Hi All,
Every Spring at this time I see a particular short lived plant in yards throughout the South (Zones 6 &7-ish). It has small pinkish-purple flowers, hairy leaves, a square stem, and grows in a fairly defined mass or colony. I think it is cross-venated with cordate leaves with crenelations. The leaves are closely packed at the top of each plant and are in groups of four oppositely-placed leaves. It is only around for a short time, tending to come out and disappear about the same time as daffodils. They aren't violets--they look more like mint, but don't have a minty smell.

My knowledge of plant morphology is too weak to work the online dichotomous ID keys, and I can't find anyone who is interested enough in the stuff to know anything about it.

I'm curious because colonies of this stuff seem to grow in a way that might indicate something in the soil and I'd like to find out if this is so.

Thanks.

the square stem is usually a sign of the mint family. not all in the family have mint smell.
here's a good site to find you culprit
http://www.wildflowers-and-weeds.com/Plant_Families/Lamiaceae.htm

the book "Botany in a Day" listed at the bottom of the page is one of the best books for plant ID

I happened across a line drawing in a Peterson Guide that led me to purple deadnettle: Lamium Purpureum. I haven't been able to find out much on what it may or may not indicate in the soils where it grows.  (I'm assuming that the reason it seems to disappear the same time as daffodils is because that is when people start mowing their lawns in the spring. I'm guessing it either gets killed or chopped down to where it becomes inconspicuous.)

I found some more info on a Dutch site http://www.infocash.nl/mens-en-gezondheid/171-de-geneeskracht-van-de-paarse-dovenetel.html

They say it's edible (the flowers and young leaves) in salads. Has lots of iron, vitamins and fibers. I'ts seeds are high in antioxidants and as a infusion is a tonicum and anticoagulant (you can also masc some leaves and put them on minor cuts) A John Gerard described some 400 years ago uses and a recipe where you bake it in sugar and raisins to make "sugarroses"

Like nettles it likes nitrate rich soil, so be careful where you collect it.

I tasted it and it's very grassy with some kind of afterbite...the Lamium amplexicaule (with leaves directly attached to the stem) tastes relatively better...