Horticulture Magazine

Penstemon Plant Care & Growing Tips

close up of purple Penstemon heterophyllus flowers

Penstemon Overview

Official Plant NamePenstemon
Plant TypePerennial Flower
Native AreaNorth America
Hardiness RatingH3
ToxicityNone
FoliageDeciduous or evergreen with simple, narrow leaves
FlowersBell or funnel-shaped flowers in various shades
When To SowMarch, April, May
Flowering MonthsJune, July, August, September
When To PruneSeptember, October, November
Sunlight

Preferred
Full Sun / Partial Shade

Exposure
Exposed or Sheltered

Size

Height
0.5 – 1M

Spread
0.1 – 0.5M

Bloom Time
June – September

Soil

Preferred
Chalk, Loam, Sand

Moisture
Well drained

pH
Any

Penstemons are a popular perennial that will bring unique beauty to your garden and are extremely hardy, being able to cope in all but the harshest of conditions.

Penstemon plants come in many varieties and provide you with a way to add great colour and interest to your garden. They’re perfect for planting in flowerbeds as well as containers and can cope very well with the harsh winter weather.

Penstemons might not be native to the UK, but you can very easily grow them in your garden and expect them to last for many years.

In this guide, we’re going to look at every aspect of penstemons, including their origins and varieties, how to grow them properly, where to buy them and common diseases and problems.

Penstemon Origins

The term ‘Penstemon’ was first established in 1748 by scientist, John Mitchell.

Up until the early 1800s, there were very few recognised species of penstemon, but this changed considerably as the century went on, with many expeditions across the States and Mexico unearthing new findings. By 1900, there were in excess of 150 recognised species of penstemon and today there are more than 250.

In the past, penstemons were used for medicinal purposes by Native American tribes, but today it’s most commonly used for show.

Although penstemon plants are native to North America, they are now popular in many parts of the world thanks to their great variety of colours and hardiness.

Penstemon mexicali cultivar red rocks flowers growing in the grass
Penstemon mexicali cultivar red rocks flowers growing in the grass

Penstemon Varieties

Below are some of the most popular varieties of penstemon plants –

Husker red

Also known as ‘Foxglove beardtongue’, this variety is very popular with growers, due to its distinctive red foliage and the fact that it flowers well year after year.

Burgundy

Burgundy is another popular variety of penstemon, and with its deep purple flowers, it makes an excellent cut plant. If you’re growing this type of penstemon, it’s a good idea to propagate it in late autumn, since it doesn’t always survive the winter.

Apple blossom

This quick-growing variety has white and pink flowers and is excellent for growing in flowerbeds as well as using as a cut flower.

Raven

Raven penstemons have deep purple flowers with white throats and flower best between June and August.

The downside to this variety is that they don’t always survive the winter, so you will need to propagate them to be safe.

Alice Hindley

These blue/purple penstemons not only look great but are a very practical variety to grow in your garden, since they cope with the winter extremely well.

Evelyn

Evelyn are a particularly appealing variety, due to their bright flowers and plentiful foliage. Although they are compact, they can grow up to 50cm high.

Feeding, Care & Growing Tips

Growing your own penstemons isn’t too complicated, but it’s still worth knowing the best way to go about it if you want your plants to thrive.

Below are all the main aspects of growing penstemons in your garden.

Planting

Before planting, you should think about where the best spot is. Although they’re able to withstand the cold very well, many types of penstemon are sun-loving, so it’s a good idea to plant them in a spot where they’ll get plenty of exposure to sunlight.

When planting, it’s a good idea to use some organic mulch as well as a fertiliser to ensure the plants take well.

When to plant

The best time to plant penstemons would be in spring or early summer. This will ensure they have plenty of time to get established before the cold weather starts to arrive in autumn and winter.

Water requirements

Generally, watering isn’t too much of a concern with penstemons, since they love the sun and can cope with dry conditions very well. You should ensure that the soil you plant them in isn’t waterlogged and the only time you’ll really need to water them is during prolonged dry spells and after first planting.

Maintenance

After your plants have become established, they won’t require too much maintenance. However, there are a few steps you can take to encourage the best flowering possible.

During the growing season, it’s always recommended that you remove any old flowers as well as deadheading any wilting blooms. Doing this will allow it to grow better and flower at its best.

Penstemons can generally cope with the cold and frost over the winter, but this isn’t the case 100% of the time. Certain varieties are not able to cope as well as others, so to be safe you should add a layer of mulch in the autumn to help protect the roots from getting damaged.   

Pruning Penstemon

Penstemons don’t require too much pruning when compared to some other plants, but it’s still a good idea to cut them back when you notice they’re becoming overgrown, or you want to remove wilting foliage/flowers to encourage new growth.

Habitat & Growing Conditions

Spring red penstemon, growing in Utah
Spring red penstemon, growing in Utah – one of the many types of climates where it can thrive

Most of the 250+ species of the Plantaginaceae family are native to North America. Given the vast size of the continent, penstemons can survive in a variety of climates and adapt to their environment very well.

They can be found growing in very dry climates, such as the Utah desert as well as more harsh climates throughout the US.

Where To Buy Penstemon

It’s not hard to find penstemon plants and seeds, whether you’re buying online or in person. There are many plant nurseries that sell them as well as websites that specialise in their different varieties.

A couple of things to bear in mind when buying penstemon are –

The variety

There are a lot of different varieties of penstemon, so if you’re looking for one particular type, whether it’s based on colour preference, growing conditions or hardiness, then you shouldn’t have a problem finding it.

Cost

The cost of penstemons can vary depending on where you buy them from, so it’s certainly worth doing your research to get them at the best price. Luckily, it’s very easy to do this when shopping online.

Wild Foxglove flower
Wild Foxglove variety of penstemon – native to Texas

How To Propagate Penstemon

Penstemons are quite easy to propagate, whether you choose to do it by division, seed or cuttings. Let’s look at propagating using cuttings first since this is generally the best method.

Using cuttings

You can take cuttings from a plant at any time during the growing season, though during the height of summer around June/July would usually be the best time.

To get started you should remove some cuttings that aren’t flowering and put them in a small seed tray that’s filled with good quality compost. Make sure the water them well after planting.

You should trim any cuttings you use until they’re roughly 4-5 inches long and be sure to trim any leaves at the top and sides to reduce water requirements and moisture loss.

Everything being well, the cuttings should take root and start growing. Depending on how many cuttings you use and the size of your seed tray, you might want to move them into their own individual pots. In any case, you should keep them away from the frost over the winter and plant them during the following spring.

Seed

Propagating by seed is another option although it’s not as ideal as using cuttings if you want your plants to be as close to the parent plant as possible.

You can propagate by seed using a heated propagator in spring; with early summer being the ideal time to put them out.

Division

Lastly is propagating by division. To do this you simply dig up a plant, divide it carefully and then pot the divided sections separately. Again, spring would be the best time to do this.

Common Diseases & Problems

Although penstemons are very hardy and generally resistant to diseases and pests, they can still develop certain problems. Below are some of the most common ones, including how to deal with them.

A bee drinking nectar from a penstemon plant
A bee drinking nectar from a penstemon plant. Thankfully, they don’t attract problem insects such as slugs and snails

Rust

Rust is a form of common fungal disease that can be spotted when see the formation of yellow spots on top of a plant’s leaves. Rust often appears during humid weather and a good preventative measure to take is applying fungicidal soap in early spring.

In addition to this, you should also remove any infected leaves and if you notice any plants that are severely infected by rust, then you should remove them immediately since it can very easily spread.

Botrytis leaf mould

Another fungal disease – Botrytis leaf mould causes brown spots to appear on infected leaves. An organic fungicide may be successful at treating infected plants, but if you notice any plants that are severely infected and look like they’re beyond saving, then you’re best removing them completely.

Powdery mildew

Powdery mildew is something a lot of plants are prone to developing and penstemons are no exception.

Powdery mildew gets its name from the fact that infected leaves will have an appearance that looks like they’ve been coated in white powder. Powdery mildew is quite easy to treat, and you can use a homemade spray containing roughly a teaspoon of baking soda mixed with water to treat any leaves that are affected.

Powdery mildew usually appears during humid weather, so you should be vigilant for it during dry periods. 

Preventing penstemon diseases

There are a few ways to prevent penstemon diseases. Leaf diseases are often spread when it’s cold and wet, so anything you can do to keep your plants dry during these times will help. Using mulch, for example, will help to prevent rain from splashing up on your plants.

Another good tip is when you’re watering your plants, be sure to be careful not to get water on their leaves. You should also be sure to remove any dead foliage you find on the ground. Proper spacing will help to ensure that your plants get enough air and circulation too.

Frequently Asked Questions

Are penstemons difficult to grow?

Penstemons generally aren’t too difficult to grow and once they’ve established themselves, you’ll be able to enjoy them for many years. As with any plants, proper care, especially after they’ve first been planted, will ensure they thrive and blossom properly.

When should I cut back penstemon?

The best time to cut back penstemons would be in early spring, once the harsh winter weather has passed. You’ll often notice new shoots beginning to appear during this time, so this is the best time to remove any old blossoms or weathered looking foliage to encourage new growth. 

Is penstemon toxic to dogs & cats?

Penstemons aren’t as dangerous to pets as some other plants, such as lily of the valley. However, they do contain Selenium, which in excess is not good for cats or dogs. This being the case, it’s usually better to keep your pets away from any penstemon plants you have.

Are penstemons perennial plants?

Yes, penstemons are perennial plants, so you can enjoy them for many years, and they can thrive in all but the harshest of conditions.

Should you deadhead penstemon?

Deadheading can be one of the best ways to encourage new growth on plants that are starting to look lacklustre and this applies to penstemons too.

The best time to remove spent blossoms would be during the growing season. If you notice any blossoms starting to decline, then you can remove them to encourage new growth.

When is the best time to prune penstemons?

The best time for pruning is in spring, once the worst of the winter weather has passed. As well as removing any dead leaves and flowers from the previous season, you should also shorten the stems of any plants whose shoots aren’t emerging.

© 2021 TKO DIGITAL LTD | Registered in England and Wales No. 10866260 | This website uses cookies. Read our privacy policy.