As we bid a fond farewell to spring and begin to look forward to those warmer summer days, we start to see dazzling Penstemons at our local garden centres. These are a little ahead of schedule when compared to those established in our gardens, as a comfortable overwintering in cold frames often brings out those abundant flowers much earlier. Which is why it is all the more tempting to purchase them and get a head start on their eye catching bloom season, but before you do, perhaps you should take a deep dive into their particular cultural needs to ensure long-term success.

Penstemon 'Cha Cha Cherry' | 📸 MK Lascelle

DRAINAGE

Sharp drainage is the most critical cultural need of Penstemons as they will definitely rot out in wet or heavy clay soils. You can assure good drainage by planting on slopes or if your parent soil has a heavy clay content, consider creating raised beds.

Penstemon 'Flock of Flamingos' | 📸 MK Lascelle

SUNLIGHT EXPOSURE

Another key component of success with this genus is plenty of sun, with 6 to 8 hours being considered a minimum and more being better. Keep in mind that we are not talking about winter exposure, but when the sun is at its peak in summer.

Penstemon 'Goldfinger' | 📸 MK Lascelle

pH

Most penstemons prefer a slightly acidic pH of around 5.8 to 6.2 so if you have very acidic soils consider adding a little dolomite lime in fall or early spring. Too much lime may cause an iron deficiency which will present as yellowed leaves with darker green veining.

Penstemon 'Harlequin Magenta' | 📸 MK Lascelle

WATERING NEEDS

While Penstemons are quite drought tolerant once established, they will need regular watering during their first summer when they are growing out a new root system. Mature plants will only need about an inch of water per week, making sure that the soil dries out between waterings.

Penstemon 'Husker Red' | 📸 MK Lascelle

SOIL TYPE

Penstemons prefer loose, well-drained sandy or gravelly soils, so avoid amending with compost or manures. A nutrient-lean sandy loam would be an ideal soil type but perhaps the most critical component is the aforementioned sharp drainage.

Penstemon 'Parade of Parrots' | 📸 MK Lascelle

NUTRITIONAL NEEDS

Most Penstemon species are native to North America and can be found in open prairie, deserts or alpine crevices. Most of these sites are naturally very well drained with lean soils, meaning that most Penstemons do not require heavy fertilization. Choose a low rated organic fertilizer such as Gaia Green All Purpose 4-4-4 which you would apply in early spring as the new growth emerges.

Penstemon 'Peptalk Cerise' | 📸 MK Lascelle

PRUNING & DEADHEADING

There are two times when you will need to prune your Penstemons, with the first being regular deadheading during the flowering season, removing the spent flower stalks  to encourage more blooms. Leave your top growth intact for overwintering as this protects the crown, but you can prune it back from April to May (once the danger of frost has passed) down to the lowest viable bud or leaf joint.

Penstemon 'Peptalk Red' | 📸 MK Lascelle

MULCHING

In colder regions or for tender varieties you can mulch for winter using about 2” of fine, well-drained bark mulch. You are essentially protecting the root system, so be careful to keep the mulch away from the crown, as this may cause it to rot out.

Penstemon 'Pristine Lilac Purple' | 📸 MK Lascelle

HARDINESS

Penstemon vary in hardiness from USDA zone 3 (prairie hardy) to USDA zone 8, which is essentially southern Vancouver Island. It all depends on the species or variety, so be sure to check the tag when purchasing your plants.

Penstemon 'Red Riding Hood' | 📸 MK Lascelle

FLOWER FORM & COLOURS

Most of us are familiar with those Penstemons with showy upright flower spikes but there are alpine species such as Penstemon fruticosus ‘Purple Haze’ and davidsonii (both of which are native to British Columbia) which are low spreading perennials which form a flowering carpet. Bloom colours range from intense purples, reds, whites, blues and pinks, many with contrasting throats. The alpine species tend to have tubular blue, lavender and purple flowers.

Penstemon 'Purple Haze' | 📸 MK Lascelle

Penstemon davidsonii | 📸 MK Lascelle

FOLIAGE COLOUR

While most Penstemons have deep green to bluish-green foliage, there are some newer hybrids such as ‘Midnight Masquerade’ and ‘Dakota Burgundy’ which produce dark purplish-black foliage. The older ‘Husker Red’ has deep red to maroon leaves with contrasting white flowers, while ‘Goldfinger’ presents with bright gold foliage when grown in ample sunlight.

Penstemon 'Midnight Masquerade' | 📸 MK Lascelle

Penstemon 'Dakota Burgundy' | 📸 MK Lascelle

So, there you have it, everything you need to know about keeping those beautiful Penstemons thriving in your garden from year to year. Now you just have to come to Amsterdam Garden Centre and choose a colour, which is the hard part.

Copyright 2026 MK Lascelle