Penstemons are among my favorite flowers, both in the wild and garden. But even though they’re an exceptionally hardy plant that does dandy without any fussing in the wild, domesticated varieties can have more disease issues. Here are a few things to watch when growing penstemon in the garden.

Here in Montana, many blue-ish and purple penstemon varieties that grow in the wild. Last year, I grew the  NOVA®’ Pearl’ variety from Terra Nova Nurseries in Oregon and am so excited about raising more that I joined the American Penstemon Society. They have a terrific seed swap that is one of the only ways to try penstemons not on the commercial market.

Hummingbirds and Bees Love Penstemon

Powdery Mildew on Penstemon

This fungal, which is prevalent in squash plants and many ve, also targets penstemons. Look for leaves with white blotches, or that look like something with white powder on them, it’s most likely powdery mildew.

Because penstemons prefer sunny, dry conditions, if you li a more humid environment, it’s even more important to plant them a sufficient distance apart to provide ample air circulation. Also, overhead watering should be reduced to minimize the possibility of a powdery mildew infection.

If your plants have it, remove the infected leaves and dispose of them in the trash. If the plants are particularly lush, consider pruning out half of it to provide better circulation. You can also spray it with one tablespoon baking soda, one tablespoon vegetable oil, and one tablespoon liquid soap (not detergent) mixed in a gallon of water. Add this to a spray bottle and spray both sides of the leaves. Reapply after every rain or watering. It will take multiple applications to knock out the infection.

Beardtongue Rust

Penstemon are also called beardtongue because their flower shape resembles a fuzzy tongue.   Besides the powdery mildew, they are also prone to rust, another fungal disease. You can identify this infection with the red-orange spores in the first part of the summer.

Once again, it usually shows up on plants when it’s wet outside and they’re planted too close together. Give them space to reduce the disease factor.

Remove any infected leaves and dispose of them. If rust or powdery mildew are yearly issues, consider using a fungicide in the spring to ward off the fungal spores. You’ll likely want to start early in the spring and continue until you’re in the safe zone for a reduced chance of an occurrence but just follow the label instructions.

Sone Penstemon are Just Not Happy

Okay, so this isn’t a disease, but penstemons are fairly condition-specific. Even though there are approximately 280 species, most of them prefer a hotter, drier climate more attuned to what we have in the West. With this said, some varieties grow well in the East and Southeast and even in jungles. Choose the right one for your location and growing conditions, or at least come close to creating the environment they prefer if you want them to act as perennials. However, if you want just to try new, pretty flowers, grow them as annuals and enjoy them for as long as you can!