Beard thread: features and care

Beard thread: features and care

Origin and Distribution

The beard thread (bot. Penstemon) is an attractive genus of flowering plants from the plantain family (bot. Plantaginaceae). About 250 different species belong to this genus, most of which grow herbaceous or woody. The beard threads, which are part of the perennials, originally come from the warm regions of North America and Mexico, where the plants thrive for several years. However, under the influence of Central European weather, the cold and moisture-sensitive plants are not hardy and are therefore mostly cared for as an annual. However, it is occasionally possible to get some robust species and varieties through the cold season with the help of good winter protection.

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  • What is the best way to overwinter the beard?


The colorful flowers as well as the tall and slender growth make the beard thread appear as the perfect companion and ornamental plant in perennial and summer flower beds as well as in borders. Its possible uses are enormous, after all the numerous single and multi-colored varieties offer a large selection. The beard thread is particularly attractive in combination with other perennials such as the summer aster (Callistephus), gypsophila (Gypsophila), delphinium (delphinium) or chrysanthemums. Species that remain low find a much noticed place in a stone or gravel garden, some also feel very comfortable as potted plants on the balcony and terrace. Large-flowered varieties - which can be found especially in the hybrids - also result in durable cut flowers.

Appearance and stature

Depending on the type and variety, the beard thread reaches heights of between 40 and 80 centimeters. The forms cultivated by us usually have a herbaceous habit, only a few species grow as subshrubs or shrubs. The stems of the beard thread strive upright and are densely covered with narrow, lanceolate leaves. These are usually arranged opposite one another. The leaf margin is either smooth or serrated.

Flowering and flowering period

The filigree flowers are similar in structure to those of the thimble. They are bell-shaped or tubular and either sit in terminal clusters or panicles. Each flower has five stamens, one of which is always covered with long hair - this property gave the genus its peculiar name. The beard thread blooms in many bright colors: white, pink, red and also purple tones bring splendid splashes of color into the garden bed. As a rule, the flowering period extends between May and August, although the beard thread can bloom well into autumn with good care and in a suitable location.

After flowering and until autumn, unless pruning is done, brown capsule fruits that contain angular seeds develop when ripe.


In contrast to the outwardly very similar thimble (bot. Digitalis), the beard thread is non-toxic and therefore perfect for cultivation in family gardens. However, both species belong to the plantain family (bot. Plantaginaceae).

Which location is suitable?

The beard feels most comfortable in a sunny, warm and protected location. Not only does it bloom all the more beautifully the more intensely the sun shines: it also needs good protection from the wind, as otherwise the flower-bearing stems can snap off or break off. A spot directly in front of a light wall or house wall or a hedge that does not cast shadows is therefore ideal. In regions with mild winter conditions (for example in the wine-growing areas) the beard thread can hibernate well protected outdoors, in all other regions you should either tend it for one year or keep it frost-free. The plant tolerates slightly frost to around minus five degrees Celsius.

Soil / substrate

Plant the beard thread in a soil rich in humus and nutrients, which should be as fresh and well-drained as possible. The plant is very sensitive to waterlogging, which can be a problem, especially in winter. It is therefore imperative that you ensure good drainage both in the bed and in a pot culture so that excess water can drain off quickly. When wintering outdoors, the beard thread must be protected from moisture and wetness. In terms of the optimal pH, the plants prefer a neutral to slightly acidic soil. Before planting, upgrade it with plenty of compost and, if the subsoil is comparatively heavy, with coarse sand.

For pot specimens, we recommend using high-quality compost-based plant or potting soil, which you can add with perlite, expanded clay (€ 17.50 at Amazon *) or sand to improve permeability. In addition, the planter must have drainage holes at the bottom so that the beard thread does not have to stand in the wet if it sloshes too much from the watering can.

Planting beard threads properly

From February, prefer the summer bloomers on the windowsill. The young plants then move into the garden bed or on the balcony from May, whereby you should definitely wait for the ice saints. Otherwise, late frosts could quickly destroy your planting. Before planting, prepare the soil well:

  • Loosen the subsoil and remove stones and weeds.
  • Make a plan of planting where which perennials and flowers belong.
  • Keep to the recommended planting distances.
  • Now dig the planting holes, which should be about twice the size of the root ball.
  • Mix the excavated material with compost and horn shavings.
  • You can also mix in a long-term fertilizer for flowering plants.
  • Lift the beard thread out of the pot and use your fingers to gently loosen the roots.
  • Put the plants in and fill in the substrate.
  • Press the soil firmly and water the plant well.

You should also provide tall varieties with a support rod when planting so that they do not kink.

Plant spacing

Depending on the type and variety, a planting distance of between 20 and 30 centimeters is recommended.

Planting time

Do not plant the beard thread outside until after the ice saints in May.

Water and fertilize

Basically, the beard thread is a very easy-care summer flower that can only cope with a little water and occasional fertilization. Planted specimens actually only need to be watered in dry phases and in hot weather, whereas you should water a beard that has been cultivated in a pot moderately. Before each watering, first do a finger test so that you can estimate the actual water requirement. Basically, strongly flowering and high-growing varieties need more moisture than the low-growing varieties.

While low beard thread varieties also get along very well on rather poor soil and only need a little fertilizer, you should provide the high varieties with a liquid fertilizer for flowering plants from time to time. However, do not start fertilizing until six to eight weeks after planting, provided you have already added compost, horn shavings (€ 6.39 at Amazon *) or even a long-term fertilizer.

Cut the beard thread correctly

Regularly remove the dead shoots so that the beard thread continues to develop new flowers. However, you can leave one or the other flower for the purpose of collecting seeds. Then just make sure to collect the seed pods in good time before they burst.

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Increase beard thread

Most beard thread types and sorts can be easily propagated using cuttings cut in summer, although these must be overwintered frost-free in any case. Propagation via seeds is also easy, although not all commercially available varieties can be used to obtain germinable seeds - most of them are non-fertile hybrids. On the other hand, you can draw non-seed variants as follows:

  • Fill a cultivation tray with nutrient-poor growing medium. (€ 9.05 at Amazon *)
  • Sow the seeds and press them lightly into the substrate.
  • Spray the substrate with water and slightly moisten it.
  • Cover the bowl with cling film or a translucent hood.
  • Put the bowl at 18 to 20 ° C quite warm and light.
  • Ventilate daily and keep the substrate slightly moist.

After about three weeks, the young plants germinate and are then pricked out as early as possible - otherwise they could become too long and kink. Cultivate the young beard threads in a cool place at around 12 to 15 ° C.

Furthermore, some types of beard thread can be divided, provided you cultivate them for several years and hibernate them accordingly.


With a little luck, some robust types of beard thread can be overwintered in the garden bed. To do this, you should cut back the plants in autumn and cover them with fir or spruce branches. If you actually want to overwinter the summer flowers, it is better to dig them up, plant them in a container and overwinter them in a light, cool and frost-free place. The easiest way, however, is to dispose of this year's plants and grow new ones from (self-collected) seeds from February onwards.

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Diseases and pests

Pests and diseases rarely occur on the beard thread. Only aphids and nematodes could pose a problem, and snails also often like to eat the plant. Powdery mildew can also occur, but it can be treated quite easily with a mixture of water and whole milk that you spray on diseased plants. Wilt disease, on the other hand, is more difficult and cannot be treated in most cases. It occurs when the beard thread is permanently in excessively moist soil and therefore the roots rot.


If you want to cut some flower stalks of the beard thread as cut flowers for the vase, it is best to do this in the early morning - experience has shown that the flowers will last the longest. Put the flower stems in a clean vase with fresh water and place them in a light and not too warm place. It is best to change the water daily.

Species and varieties

The varieties available on the market are almost exclusively hybrid forms, some of which, however, look very similar to their parents and can therefore hardly be distinguished from them. Some pretty shapes for the home garden are for example:

  • Penstemon barbatus 'Coccineus': up to 120 centimeters high, bell-shaped, bright red flowers
  • Penstemon barbatus 'Praecox Nanus Rondo': bushy growth, up to 40 centimeters in height
  • Penstemon digitalis 'Dark Towers': clumpy growth, height of up to 90 centimeters, purple-pink flowers with white tips
  • Penstemon digitalis 'Husker's Red': clusters-forming, up to 100 centimeters in height, large, white flowers arranged in panicles
  • Penstemon scouleri 'Catherine de la Mare': upright growth, height up to 40 centimeters, azure blue flowers arranged in racemes
  • Penstemon hartwegii 'Picotee Red': flowers bright red
  • Penstemon hartwegii 'Schönholzeri': flowers strikingly scarlet