This is a plant with many names, hardy hibiscus, rose mallow, swamp mallow, etc. It is a wonderful plant and should be in almost every garden.
A North American native it can be found growing wild in the south, but it has been hybridized and many beautiful cultivars are available for the entire country. It is related to the tropical hibiscus but is hardy and has much larger flowers. These flowers can get to a foot across, a full 12 inches, outside of dahlias, which are a huge labor to grow, what else gets so big?
These plants are fairly carefree. They need sun, and water, that is about it. I’ve given some to my Mom and while deer eat most other things I’ve given her, the deer near her house (and she has a lot of deer) have never touched these. Maybe, because they’re native, they evolved with deer and so have defenses.
They get a late start in Spring, I often worry they have died (and I sometimes protect them with a styrofoam cone to allow them to get an earlier start, but they don’t need it), by late May they’re growing, reaching as high as 4 feet by late summer, then the blooms come. Mostly in shades of white, red, and pink. The plant also has a very pleasing golden fall color to the leaves.
Standard hardy hibiscus have heart shaped leaves like other members of the mallow family. However some hybridizations have occured for leaf interest as well. My favorite of the lot is called ‘Pinot Noir’ it has very deep cut foliage remisicent of a Japanese maple, the leaves are also mottled green and purple, though the purple is very subtle. There is also ‘Kopper King’ which has three lobed leaves like a standard maple that feature a bronze or burgundy sheen. I also grow a variety called ‘Turn of the Century’ that has green leaves otherwise deeply cut like ‘Pinot Noir’ or maybe even more so. ‘Turn of the Century’ also features striped red and white blooms that look like peppermints. Finally I grow a white one that I’m unsure the cultivar of.
Of the four I grow ‘Pinor Noir’ my favorite for it’s deep red blooms and colorful leaves, is also the hardiest, and the best grower for me (though perhaps that is my fertilization bias). We had a spat of cold weather about 10 days ago with our first frost. It affected the other ones slightly, but ‘Pinot Noir’ is still sitting pretty like we’re in mid August.
In the Spring or early Winter after you’ve had some hard freezes you should prune back the growth to the ground, those canes are dead and you don’t need to keep them (this isn’t a hydrangea).
Make sure the plant gets plenty of water when growing, and they should grow well, with plant and bloom size being related to soil fertility. I also have anecdotal evidence they like banana peels, I toss a few into my garden daily, and the plants really seem to respond to that potassium.
All told I can’t recommend the plant enough. It is easy to grow, carefree, and provides showstopping blooms. It is also very easy to start from seed, every year one or two volunteers crop up in my garden (enough to be a bonus, way too few to be invasive). After blooming small seed clusters develop which eventually turn brown and crack open, harvest the seeds then and try planting them, maybe you’ll discover a new color! Or perhaps, you’ll just get free plants.