Q – Someone told me that penstemons are very attractive plants to grow in a border, is that true?

A – Penstemons are a rather flamboyant member of the snapdragon family.  With their elegant spires of foxglove-like flowers in a range of beautiful reds, pinks, purples, blues and whites, they are ideal for adding colour to your border from June onwards. Developed from a species introduced to this country from Mexico, Penstemons were considered fashionable by our Victorian ancestors and today, they are as popular as ever. They are easy to grow and ideal for new gardens as they are quick growing and colourful.

Most hybrids start flowering between mid June and early July, with the main flush of flower lasting six to eight weeks followed by a lesser display of flower from side shoots which can go on even into October. By planting different varieties with different flowering times you can have a mass of flowers for a good four months.

Penstemons grow well in a sunny place, ideally in a rich, fertile, well-drained soil in a place that is protected from the worst of winter winds. Regular deadheading prolongs flowering and it is worthwhile cutting them back by about half when flowering fades. Cut them back again in the spring to encourage more prolific displays.

After about three years they will be over their best, so replace them with new Penstemons; the good news is that they are naturally resistant to pests and diseases. However they are occasionally thought of as being rather tender.  Generally speaking the narrower the leaves, the more hardy the plant is over winter. They can be damaged by severe frosts, which is another reason to cut them back hard every spring. In fact winter losses are often the result of poorly drained soil or the crown being smothered by fallen leaves and left to rot.

Penstemons fit easily into a mixed border, amongst dwarf shrubs or other perennials. Shorter varieties can be used as summer bedding planted amongst your lobelia and petunias.

Try planting the larger varieties with old-fashioned roses; the penstemons will start flowering just as the roses pass their peak. Hardy geraniums are also good companions as they nestle around the base of the penstemon hiding its bare, woody lower stem. Some varieties, such as Alice Hindley and Rubicundus can reach 1.2m in height. If you need to reduce their height, try pinching out the tips after planting.

Good companions to the more compact varieties, such as Apple Blossom or Evelyn, include trailing verbenas, osteospermums, argyranthemums or silver leaved helichrysums. If you prefer deeper colours try planting Port Wine or Raven with dark leaved cannas or dark dahlias.

There are also a large number of dwarf Penstemons for the rock garden. These make tiny shrubs, often with a creeping habit and need full sun with a well-drained gritty soil. They are ideal for raised beds and they help prolong the display into the summer as they flower a little later than many other alpines.