Penstemon – Penstemon hybrids

Sparkling, bell-shaped flowers. With their spiky shape, beautiful flowers and handsome foliage, penstemon hybrids bring joy to the summer garden. They have a longflowenng season and their jewel-coloured blooms, when massed, are spectacular.



Late April-May:

Plant out young plants in their summer positions.

Make sure they are not exposed to drying spring winds.



Flowering time.

Water in dry spells to keep flowering at its peak. Take cuttings from side shoots for next year’s plants.



Pull out plants which you do not want to grow next year. Cut down the stems of the remaining plants, and cover with mulch and a cloche (domed cover).

Move plants in exposed sites to a better position.



Sow in seed-trays or pots in gentle heat (13-18’C). Use clean pots and sterilized compost to prevent disease infecting the seedlings. Keep the humidity down to prevent damping off (rotting).


Cut stems down to just above ground level. Cover the crowns with a 5cm mulch of leaf-mould or sim- ilar compost. Put a cloche (domed cover) over the top, and remove it in spring after all danger of frost is past. Even when penste-mons survive the winter, make sure to shelter them from winds in the spring.


Plants grown from seed or cuttings flower very freely for the whole of their first season. Those in their second year or more make a riotous display in June and July, but give only a sprinkling of colour afterwards. If you find a colour which you value, take cuttings from that plant in summer and overwinter. Each year’s display will be at its peak if you propagate plants every year.

Y ou can use these brightly coloured, tubular flowers for summer bedding on their own, or to provide colour in herbaceous beds as border plants.

Penstemon hybrids are bred to be hardier than their mainly tender parent species from southern North America and Mexico. But even the hybrids are not reliably hardy outdoors in British winters except in the warmest, western counties and seaside areas.

Grow from seed

There are several ways you can grow penstemon hybrids. Grow them from seed, sown early, in February or March. Sow the seed in gentle heat, 10-13°C, under glass or indoors on a south-facing window-sill.

When the seedlings are large enough to handle, prick out (replant to give them more room to grow), one to a 7.5cm pot or 5cm apart in seed trays. In April start to harden off the plants by putting them outside in the daytime and giving protection at night to avoid frosts. By May danger from hard frost should be over and you can plant them outside in their final positions. Alternatively, buy young plants and plant them out in May.

Take cuttings

To overwinter plants reliably, take side-shoot cuttings from the plants in summer and root them in sand or perlite (volcanic granules). Keep them frost free throughout the winter and plant out the following May after hardening off. They flower earlier from cuttings than from seed.

Some perennial hybrids can successfully overwinter in the ground outside.


If your penstemons are an annual display, remove the plants after they have finished flowering and compost or burn.

Dig the site over in the winter and incorporate manure or compost. If you succeed in cultivating them outside as perennials they will be short lived, 3-5 years usually.



Give full sun in a warm part of the garden, preferably in a south-facing border. This is especially important if you wish to overwinter plants outdoors. Avoid exposed, windy areas.


Free-draining, light soil is best; never waterlogged, cold or frosty. Incorporate organic material to improve soil structure and provide nutrients. Add sharp sand to heavy soils.


Little is required once penstemon is planted outdoors, apart from watering thoroughly if drought threatens. Without water they wilt and stop flowering.


Penstemon is usually free from pests and diseases. It can sometimes fall prey to chrysanthemum eelworm, also known as leaf and bud eelworm. The leaves and young shoots are distorted and discoloured and the plant’s growth is checked.

Eelworms live in and on the leaves and buds. Avoid bringing infested plants into the garden, and buy only from’a reputable source. If established plants show symptoms, dig them up and burn them, otherwise they may infect other plants.

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