Penstemons have become a very popular garden plant in recent years.
They flower for a long period of time and require little or no care. Years ago they were regarded as unreliably hardy in most gardens and needed to be over-wintered in a greenhouse. In recent years, the winters have been milder so most varieties can survive outdoors.
Plants will sustain some frost damage in most winters and this damaged growth can be cut back in late March or early April. Lightly trimmed early in the year, the plants will flower from June onwards.
The penstemon is related to the foxglove and the flower shape in both plants is very similar. The trumpet-shaped flowers are produced on tall stems which are not as rigid or as tall as the foxglove.
The flowers are smaller than the foxglove. The advantage of the penstemon is that the flower lasts for a longer period of time before shedding and the plant also flowers much longer than the foxglove. The penstemon has a far better range of colours than the foxglove. The penstemons come in a wide range of colours guaranteed to suit all tastes. The colours range from white and palest pink, through bright scarlet red and pale blue purple, to deep magenta.
The main flowering starts in summer and continues into mid-autumn with some varieties. Penstemons vary in height between 18 inches and 4 feet, there are also alpine varieties. Cutting off the old faded flower stems will encourage stems lower down to grow up and flower.
Penstemons are generally grown as a border plant but in recent years with smaller gardens, the plant is often used in the same way as small shrubs. It is not a true shrub but the stems have woody bases and grows about the same size as small to medium size shrubs. Penstemons produce many flowers and flower for such a long period, they will perform better than most shrubs.
Penstemons like a well-drained soil, the addition of a small amount of well-rotted compost will give the plant a boost without encouraging too much sappy growth.
They like a sunny position but they can also cope with dapple shade or a spot that gets brilliant sunshine for only part of the day. Do not plant them in deep shade.
There are many varieties to choose from: Penstemon ‘Garnet’ has deep wine red flowers, this deep colour sets off so many other plants. It is reliable and a hardy variety. Unfortunately the name of this plant has changed to ‘Andenken au Friedrich Hahn’, which is something of a mouthful. Penstemon ‘Evelyn’ is a variety with small rose pink flowers. Penstemon ‘Apple Blossom’ has very pretty pale pink flowers with white throats. Penstemon ‘Maurice Gibbs’ has large cerise red flowers with white throats. Penstemon ‘Sour Grapes’ has greyish blue flowers with tinges of purple.
It is always a good idea to take some cuttings in mid-summer each year as an insurance against losing your favourite plant to frost in winter.
They root easily and grow fast to replace any lost plants. Choose a healthy shoot produced lower down a flowering stem. Root cuttings in a mixture of peat compost and sharp sand. Once rooted, pot up into 4 inch pots and over-winter in a cold frame or greenhouse before planting out the following April or May when the risk of frost is over.
Jobs for the week
Collect seeds from your favourite perennials and store them in a cool dry place.
This is a good time to take cuttings of your favourite roses, stems about nine inches long are cut below a bud. The cuttings are inserted in a trench in the open that is sheltered from north and east winds. Place a layer of sand in the bottom of the trench to improve drainage. Place the cuttings about four inches deep in the trench.