In my experience, you can't help but have large areas of geranium macrorrhizum.

I bought a one-gallon container of it some years back, and divided it in half after bloom its second year in my garden. Both new clumps multiplied joyfully, and I divided each in half again the third year, after bloom in early summer.

The fourth year, I brought containers into the office to share with anyone who wanted some. That time, I divided it just as buds started to open, so that people could see it blooming. Big hit.

Fifth year and every year since, I've dug up geranium macrorrhizum and tossed it away whenever I noticed it overstepping its bounds. Seems you can't kill it, and it'll settle in happily wherever/whenever you divide and plant it.

Good, thanks! I know it's easy and will thrive anywhere. I've got a big area under a tree, which slopes down to the driveway and it's hard to mow. The grass has gotta go and the g macrorrhizum is the replacement. I got the original plants at a swap (always a good sign that they multiply), and I love them! So the more the merrier.

The thing to watch on it is that it can travel a fairly large distance from where the root is in the ground. So a lot of times when I am digging it up, I have a lot fewer divisions than I thought.

Yeah my other geraniums are like that.... I'm hoping it will seed itself as I've left all the seed pods on.

If you are short on time, use good hand sized hunks with roots. Throw them on the ground you want covered. Put some dirt over them. Water regularly. They'll grow well with this abusive treatment.