Penstemons are tough perennials that can stand up to some pretty intense growing conditions. The tiny alpine species, native to North America, can grow in the cracks of rocks and stand up to extremely cold weather, while others grow in disturbed soils in prairie settings. No matter where they’re growing, penstemons need extremely well-drained soils and will not tolerate wet soils, especially over the winter. The prairie-type penstemons are much more tolerant of standard garden soils, whereas the alpine varieties require very sharp drainage, similar to what is found in gravel gardens and even trough gardens. No matter what type of penstemon you plant, all perform well in fairly nutrient-poor soils and will tend to put out too much tender growth in rich soils. Penstemons also need full sunlight to perform their best. Not only will this ensure that they put out quality blooms, but it will also prevent them from flopping and reduced the risk of the plant developing powdery mildew on the leaves, especially in humid summers. After the plants have bloomed, penstemons will produce copious amounts of seed. If you are hoping to have your penstemon plants freely seed around your garden, make sure to leave a few stalks on the plants so they can fully ripen and disperse. Otherwise, you can remove spent blooms to encourage a second wave of flowers.