Over the past 10 years or so I've tried at least 20 different varieties here. A few were unhappy, a few looked good for a short time and then mysteriously disappeared but most of them became wonderful additions to the garden.
First of all, when people think of Geraniums, they tend to think of the hot house variety that are not hardy here in zone 6b. Those are really named Pelargoniums and Geranium is just a nick-name. On the other hand, plants with the nick-name Cranesbill are really named Geranium. I know, it's confusing but just stick to Hardy Geranium and you should be ok.
The first variety I grew here and probably the first for many other people too was a common Geranium sanguinium. My variety is purplish but there are other colors too. I've tried the pink with little luck but would like to try a white bloom now.
A friend shared a piece of Geranium cantabrigiense 'Biokova' which quickly captured my heart. It's just coming into bloom now so I'll wait a few days before sharing a good photo. Once I saw that this variety came in another color, the pink version named 'Karmina' I was hooked and started looking for more Geraniums.
(How could this lovely hardy Geranium be called a weed. I sure wish I knew it's name.)
Many years ago I was walking at Fox Hollow Farm, a perennial nursery that used to be in business just a few doors down the road. Growing out of a crack in the ground cloth was an interesting leaf that I thought might be a hardy Geranium. I asked the owner if I could dig it and buy it. His answer was that anything growing out of a crack was a weed and I could have all the weeds I wanted free of charge. That Geranium came home with me and although I don't know it's species name, it's one of the best here in my garden. Growing in a spot with no added ammendments, lots of shade, no water during dry periods and right near the road, it's become a huge, glorious clump. I've been sneaking off pieces to move here and there and finally will have enough next spring to share.
It took me a few years to learn that the different types of geraniums require very different growing conditions. The darker leaved varieties (so called purple foliage) really require a good amount of shade. Don't think your Geranium maculatum 'Espresso' died if the foliage disappears. Sometimes I find the dark leaved varieties go dormant during the summer heat.
Over the next few weeks I should be seeing many more hardy Geraniums come in to full bloom. There's 'Cambridge' out back, lots and lots of 'Phillipe Vapelle' spreading around, the fantastic wlassovianum in the shade bed (just try to pronounce that one) and more, some are so new they're still in their pots.
Stay tuned for more on the hardy Geraniums. I'm off to a garden club meeting and I have a terrible urge to go on a shopping spree after the meeting :-)