Legalily said:We get below 0 temps. Some can't handle the hard freezes.
With snow cover i imagine?
Consider Cold-Hearty Succulents like Sempervivum and Sedums! I plant these exclusively where I live in the Pacific Northwest. Sempervivum and Sedum originated from Alpine regions in Northern and Eastern Europe and they are used to cold dry Winters. In fact they thrive in that climate. In the Wintertime Sempervivum go dormant. So it looks like they aren't doing anything because they aren't! Sempervivum and some Sedum are often hardy down to Zone 4 and poss Zone 3. Semps (as they've been nicknamed) appreciate a Winter snow cover as it keeps them insulated. What they don't like is having wet soggy roots! Planting Sempervivum in the ground in an area with decent sun exposure (dont need FULL SUN, and in fact like a bit of a sun break in Summertime, even if its the shade from a perennial, a rock, or a few tall strands of grass adjacent), in non-rich (boring) soil topped with a few inches of course gravel or chicken grit, and theyll do just fine in Iowa!
You may know them as 'Hens & Chicks," yet this nickname doesn't do this genus of plants justice. Last I heard there are more than 5,000 named Sempervivum. The color changes they go through in the Springtime are absolutely spectacular and it's very easy to fall in love. They come in all different sizes from very small(less than an inch) to very large (over 12in).
I find that even if I'm growing a larger variety of Sempervivum, if I put it in a small pot they'll behave like goldfish--growing only to the size of their container. Check out the Sempervivum forum!!
I'll attach some pics of my planters. FYI my Sempervivum can tolerate much lower temperatures than some of the pots in which I plant them. You can bring them indoors or garage for Winter if the container is not frost-proof. Just place them in the sunniest window possible if inside. Sempervivum get their best spring color when the nights are cold and the days are sunny. Here's some pics of my pieces I sold to clients: