My experience is that it spreads primarily via self-seeding, so with a little attention (e.g. with a hoe) to these seedlings, you should be able to keep it in check.

Personally, I have never had any of the macrorrhizum cultivars self-seed. I grow Spessart, Ingwerson's, Bevan's, and variegatum. The first three all spread in a slow and steady manner, so the clump increases in diameter annually. This is in part shade and fairly dry clay soil, UDSA zone 4. The macrorrhizums are evergreen, even in the north, so that limits what you want to grow with them. I grow vigorous bulbs such as narcissus or tulips next to, but not through, a clump of ger.macrorrhizum. Variegatum is much less vigorous, even a bit temperamental to grow. It needs a moist, partly shady spot and a bit of "babying". Except for variegatum, these are definitely meant to be used as groundcover rather than in a special spot in the border. They are super plants for dry shade under trees or next to a building and rarely need supplemental watering. If you have a large mass of them, they can get a bit boring when not in flower. I love the fragrance of the foliage, but not everyone agrees with me. Each to his (or her) own. I don't like the smell of lamium maculatum or salvia superba.

The 'Biovoko' variety is a cultivar of the macrorrhizum which I have and it is pretty manageable and spreads slowly. I believe I have seen the plain macrorrhizum in another garden and I declined taking any of it, because I thought it spread way to fast for me. I also thought they got a bit boring after bloom, because they become such a large expanse of plain green. I really dislike the fragrance of the foliage on all Cranesbill, but they are such a useful plant in part shade, I keep them around, plus mine turn a nice red in the fall. Not the most exciting plant in my garden.

Please note that 'Biokovo' is a variety of Geranium à cantabrigiense, which is a hybrid between G. dalmaticum and G. macrorrhizum.

In any case, it still spreads, but does not self-sow, so is usually considered somewhat better mannered, and therefore may be a better choice for Donna. The foliage is also darker green and somewhat glossy. There are several varieties.

Thanks very much! This gives me a better idea of how to use the plant.

Donna