I was ask that question and my answer was a group of plants of many flowers. They are native the North American. There are tall flowers and many are found in rock gardens.Colors range from white to blue. The hummingbirds like them. Some Are not hard especially the red ones that are in southwest states. They are subject a fungus after a few years and need to be replaces. They easy increased by cuttings. Growing from need two month in moist moisture to germinate. They last long s cut flowers. Most of all are not scented. These are a few of my penstemon photos.
idahobluebird50 Plants, Animals, Cats, Dogs, Mysteries and Chat 
I learned something new, I didn’t know anything about that flower. Thanks.
You are such a wealth of knowledge about plants and animals. Thanks for sharing as I learned a lot!
Thanks!
Very pretty and I learned something new today.