Gloria ...
I happen to know more about roses than any other plants, but I had thought I wanted to used heucheras to create a foliage garden using the various colors of foliage to create contrast and texture. They also tolerate poor soil and have few plant diseases. Sounded pretty good to me.
Heucheras are rated in the AHS A-Z Encyclopedia of Garden Plants to be viable plants in Heat Zone 8, which is where I garden.
Typical of me, I started doing some research on the location of where the species grew and the lineage of the plants on the market ... especially those marketed as being heat tolerant and created a small database. I also checked many of the sites selling heucheras to identify which plants they considered to be heat tolerant.
My very, very basic research showed me a major flaw in how Heat Zone information appears to be presented. (I am going to stick with the heucheras for now because my database is readily accessible to me.) When heat zone information is supplied for a plant, it seems almost like a "stand alone" variable, but plants that can survive and thrive in a humid heat zone 8 will struggle in an arid heat zone 8.
Back to the species and the lineage. Most of the huecheras said to be heat tolerant contain H. villosa, which is found in the southeast US in humid climates. Heucheras that are heat tolerant in an arid climate generally contain H. micrantha, which is found in the more arid climates of the western US. (Note: H. micrantha is native to Trinity County where I live.)
I think heat zone information is vital to plant selection as it is the heat of my summer temps that has a more detrimental impact to my garden than the cold of winter.
Smiles,
Lyn
