Plant guide: Penstemon
Penstemons are an invaluable plant for late Summer colour.
A bushy, herbaceous plant, they produce tall, flowering spires, covered from July onwards with rich-coloured tubular or trumpet shaped flowers. If you’re a fan of their stately elegance, you’re in luck, because there are hundreds of varieties to choose from, with an ever-increasing choice of flower colours, in gorgeous jewel tones of pink, purple, blue, white and red.
Botanical name: Penstemon
Plant type: Semi-evergreen perennial
Penstemons flower each year, and retain most of their leaves over the winter months, in all but the coldest years.
Despite being perennials, penstemons are fairly short lived, and need to be replaced every three to four years. They are easy to propagate, so you can take cuttings in the summer and grow new plants for the following year.
Growing conditions:
Penstemons grow best in full sun. In colder parts of the country, they might need protection from winds and would appreciate the shelter of a wall or enclosed area. They prefer fertile, moist but well-draining soil. If your soil conditions are drier, or less fertile, dig in some well-rotted organic matter just before, or at the time of planting, and mulch once a year in Autumn to help increase fertility and keep moisture levels in the soil. They don’t grow well on heavy clay soils, but if you have this soil type and really want to grow penstemons, then digging through grit before planting can help.
Penstemons typically grow to around 60-90cm tall, so tend to do well in the middle of a border.
How to plant:
Plant in the Spring, between March and May, to give the plant enough time to get established before flowering. Dig a hole as deep as the size of the pot and about twice as wide. Squeeze the sides of the pot, to release the compost and gently remove the plant with the compost still attached. Place in the hole and back fill around it with some of the earth that you have removed. Firm in place and water well.
Care:
Water for the first growing season, especially during any long periods without rain. Once plants are well established, they shouldn’t need watering, unless you’re growing them on especially dry soils.
Once the plant starts to produce flowers, deadhead regularly to encourage more flowers to grow.
As it’s a semi evergreen plant, the foliage usually stays in place over the Winter months, though it can start looking a bit tatty. It’s best to leave it on the plant until Spring, even if it is looking a bit straggly, as it helps to preserve the plant’s energy and it can better cope with winter conditions. Once new shoots start to appear in the Spring time, usually around March, you can cut back the old leaves right to ground level.
There is usually no need to stake penstemons, as their stems are sturdy. If you are gardening in an especially windy spot, or growing a very tall variety, then staking in Spring may be helpful.
Grow with:
Perfect to grow alongside other cottage garden plants that flower in late Summer, such as Erigeron karvinskianus (Mexican fleabane), echinacea, asters, dahlias, Japanese anemones or salvias.
Uses:
Penstemons make excellent cut flowers, their towering spires looking really striking in a vase.
Sear the ends in boiling water for 20 seconds before arranging in a vase, to keep the stems from wilting.
Our favourite varieties:
Penstemon ‘Raven’ is our all-time favourite: a deep purple flower, tinged with white inside the flower’s “throat,” set off against green leaves. (Pictured above.)
‘Dark Towers’ is a really unusual penstemon, with dark burgundy stems and white flowers.
‘Snowstorm’ is a white-flowered variety, that blooms for months on end, all the way through Autumn.
