The firecracker penstemon is aptly named---its tubular flowers are a striking fire engine red and explode from the plant in a profusion of blooms on tall flower spikes that resemble fireworks. Known botanically as Penstemon eatonii, this wildflower is sometimes called Eaton Penstemon, Eaton Beardtongue or Scarlet Bugler. It grows to four feet tall and needs full sun and well-drained soil. It can tolerate cold temperatures and drought conditions and is a good addition to a butterfly or hummingbird garden. Gardeners are advised not to water this plant after if it is established. If you live above 4,000 feet in elevation, you can grow this wildflower in the Western United States, from northern Idaho to the Mexican border.
Check plant for new growth starting to form as buds from the base in April or May.
Prune off all old flower spikes from last year's blooming at the base in April or May after you see signs of new growth, but be careful not to cut into the plant's base itself. This penstemon readily self-sows, so if you want to grow additional plants, scatter your cut flower spikes in the area where you'd like to have more "firecrackers."
Cut back all old branches that do not have flowers at the same time, in April or May. Be sure not to cut into the plant's root system or base with your clippers. It's best to prune each branch one at a time rather than wholesale lopping them off with hedge clippers or a similar tool.
Cut back flower spikes after their last flower fades any time in mid summer---doing this can help to encourage the plant to bloom again.
Prune all foliage about one third of the way to the plant's base in fall to encourage it to bush out and also to leave enough foliage to help protect it from cold temperatures.