Culture Report: Penstemon offerings reach new heights
Penstemon, as a class, scores high with consumers for appeal for many reasons. It is generally an easy-to-maintain garden choice, a main pollinator attractor (bees and hummingbirds in particular) and is available in colors that help customize outdoor spaces.
(Shown above: Penstemon ‘Mountain Treats Rose’)
For much of the continent, penstemon also has value as a perennial, specifically the P. barbatus types, which are hardy through USDA Zone 5a. Perennials are seeing a resurgence in the marketplace due to new housing construction and the emphasis on economic savings: plant it once and enjoy it for years.
My role as product manager puts me in a unique position to evaluate trials and identify when new plants in the industry provide a grower solution. Ideally, these new introductions outperform their commercial counterparts, perform better for the grower, and/or launch new or improved colors the end user is seeking.
Launched at California Spring Trials in 2025, Mountain Treats and Summit Sweets are two brand-new series of penstemon from Darwin Perennials that fill a height gap in this class. These intros now cover a wider variety of garden heights, plus add trending colors and reliability for added market appeal.
This is your go-to border placement penstemon, with a more compact flower spike and reliable overwinter hardiness to Zone 5a.
PENSTEMON MOUNTAIN TREATS
This series launches in five colors as a mid-height, mid-vigor option for perennial growers. All five colors are vibrant and the large bloom size is a beacon for hummingbirds. It is hardy to Zone 6a.
‘Mountain Treats Lavender’
‘Mountain Treats Pink Light’
PENSTEMON SUMMIT SWEETS
This series has two varieties, Ruby and Purple, and retains a Zone 5a hardiness. It’s the tallest of the penstemon series, with a landscape height that is impressive but still manageable at retail. It’s perfect as a thriller in mixed combination.
I would recommend growing and offering both series to your customers for a well-rounded assortment. The following guidelines and support tips will help your production be a success.
PROPAGATION
For spring sales around week 18, use an unrooted cutting (URC) input. Stick the cutting week one into your liner of choice. Rooting hormone is recommended at a rate of 500 ppm IBA. This information is based on a 72-liner taking roughly eight weeks to finish the liner and nine weeks to finish a 2.5-quart pot.
Apply a pinch in the liner stage. A low mist is needed, and keep the root zone temperature around 70° F. Do not oversaturate the rooting media.
FINISHING
Extending your day length with lighting will bring penstemon into bloom earlier; 12-hour days are recommended. Penstemon are long-day facultative.
Monitor your watering schedule, as penstemon prefer to grow on the dry side — ideally a 2.5 to 3 on the moisture scale. Allow the media to dry moderately between watering. Media pH should range between 5.8-6.2.
I recommend a preventative drench of a broad- spectrum fungicide and scout for spider mites and thrips. Finishing temperatures should range from 55° F to 70° F at night and 60° F to 80° F during the day.
CROP SCHEDULING
All three Darwin Perennials penstemon series are first- year-flowering. This makes for easier scheduling and production, as they can all be grown and finished the same. Growers will also experience a shorter crop time, which increases margins in perennial sales.
While Mountain Treats and Summer Sweets are more vigorous and taller, a 2.5-gallon perennial program works if you can move them quickly. I would also recommend a 1.5-gallon or 10-inch color pot for retail. Place them as thrillers in a combo pot for additional premium sales.
Penstemon bloom May through July — just when the heat of gardening season takes place — and they’ll attract bees and other pollinators for more interest.
Offer all of these penstemon size and habit options to your customers as shoppers continue to search for perennial color.
Photos courtesy of Ball Horticultural Co.
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