Penstemons: Gorgeous, and the Thing I Drowned in Two Weeks
Okay. We need to talk about penstemons, because they might be the best argument for xeriscape in this whole valley, and because I killed one in a genuinely embarrassing way and you should learn from it instead of repeating it.
Penstemon is a huge family and a bunch of them are straight-up native to Utah. Firecracker penstemon, Palmer's penstemon, Rocky Mountain penstemon, all of them tough, all of them gorgeous when they bloom, all of them built for exactly the kind of dirt and dry summer we've got up and down this valley. If you want a plant that says "I belong here" without you doing much of anything, penstemon is it.
Here's the embarrassing part. My first one, brand new in the ground, I watered it every single day for two weeks because it looked thirsty to me. Wilted a little in the afternoon heat, perked back up in the evening, totally normal penstemon behavior, and I panicked and watered it anyway. Every day. In alkaline clay that does not drain. I drowned that plant standing up. It never had a chance.
I tell that story a lot because I think it's the real lesson of this whole module, not just the penstemon lesson. Over-watering kills more of these plants than drought ever does. New plants need consistent water to establish, and then you have to back way off, and backing off is the hard part. Nobody struggles with under-watering. Everybody struggles with trusting the plant to be fine when it looks a little sad in July heat.
What penstemon actually wants
- Full sun. Most varieties want six or more hours. Shade makes them leggy and sad.
- Fast-draining soil. This is not a compost-and-amend situation. Go back to the lousy dirt lesson if you skipped it. Penstemons in rich, wet soil rot at the crown, which is exactly what I did to mine.
- Water to establish, then almost nothing. First summer, water deeply maybe once a week, less if we get rain. Second summer on, most established penstemons in this valley want occasional deep water in the worst heat and that's about it. Some varieties, once they're in, can go most of a summer on nothing.
- Room to breathe. Don't crowd them. Air circulation matters more for these than for a lot of plants, especially with our humidity spikes in a wet spring.
Buying and planting, practically
Buy small. One-gallon or even quart-size penstemons establish faster and cheaper than the big dramatic five-gallon ones. I'd rather you buy three small plants than one big showy one. The small ones catch up within a season or two and they handle transplant shock better, which matters a lot for a plant that hates wet feet while it's adjusting.
When you plant, dig the hole a little wider than the root ball but not much deeper, and do not baby the soil with amendments. Backfill with what came out of the hole. If your dirt is heavy clay, work in some coarse material for drainage, gravel or decomposed granite, not compost. Compost holds water. Water is the enemy here, at least once the plant is settled.
Water it in well the day you plant. Then water again in a few days if it's hot. Then start stretching the gap. By week three or four, you should be watering way less than your instinct wants you to. That instinct is what got me. The plant looks a little wilted in the afternoon sun, you assume it's thirsty, you give it more, and you drown it slowly over two weeks without ever seeing what's happening underground.
A story about grandma's yarrow, sort of
This part isn't really about penstemon, but it's about the same idea, so bear with me. My grandmother grew yarrow, actual old-fashioned yarrow, the kind with the flat flower clusters, and a few years back I dug up a chunk of it out of a cousin's yard in Idaho and drove it home in a bucket in the back seat of my car. It's by my mailbox now. I call it Grandma's yarrow and at this point most of the ward knows about it because I mention it constantly.
The reason I bring it up here is that yarrow gets the same treatment penstemon does from beginners. People see it looking a little rough in August heat and want to rescue it with water. Meanwhile that plant has survived on total neglect by my mailbox for years. These tough old plants, the ones our grandparents grew because that's what grew, they're tough because they don't need us hovering. Penstemon's the same. Once it's in and established, the kindest thing you can do is mostly leave it alone.
Which penstemon, if you're picking one
For a beginner in this valley, I'd start with Firecracker penstemon if you want red and hummingbirds, or Palmer's penstemon if you want that soft pink and a plant that reseeds itself generously, sometimes a little too generously. Both handle our alkaline soil without complaint. Both bloom for a good stretch if you're not overwatering them into rot.
Before next time
Pick one penstemon variety you like the look of and figure out where in your yard sun map it would actually go. We'll be building it into your layout soon, and I'd rather you come with an opinion than a blank spot.