Buddleia is a beautiful plant that produces large, showy flowers and attracts butterflies and hummingbirds. The flowers last for weeks in the garden, but people still have many questions about what to do with them once they have finished blooming. This article will answer some of your questions on what to do with your Buddleia after flowering so that you can enjoy this colourful addition to your garden all year round!

Buddleia in Flower
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What is a Buddleia?

Buddleia is a hardy perennial that grows throughout the world although they are considered invasive in Europe and Australasia. The genus Buddleja of flowering plant in the family Scrophulariaceae numbers about 140 species. Most species of Buddleia are shrubs that are under 5m tall, but some species are beasts that can even be considered trees as they grow to a staggering 30m tall!

In the UK, we have a shrub variety, and they are commonly known as butterfly bushes because they attract butterflies to the garden to feast on their plentiful nectar.

What Buddleia Varieties are there?

There are three main species of Buddleia and countless cultivars and hybrids

  • Buddleja alternifolia – Strongly overhanging and arching species with tufted flower spikes. Combines well with climbing roses.
  • Buddleja davidii – original species of the countless Davidii hybrids with long, conical flower panicles with a wide range of colours from white to dark purple.
  • Buddleja globosa – Rare, yellow-orange flowering species that is cultivated more as a container than as a garden plant in this country.
Butterfly on a Buddleia Flower Head
Butterfly on a Buddleia Flower Head

What Does Buddleia Look Like?

Depending on the variety, they grow broadly upright or squat and form a loose, funnel-shaped crown with strong main shoots and loose side branches, the tips of which often hang slightly under the weight of the flowers. The largest varieties grow up to four meters high, the smallest about one meter. Its bark is light brown, and the narrow, oblong leaves are opposite and lanceolate. They are grey-green and have grey-felted undersides.

What Happens When Buddleia Flower?

It is hard to say how long a buddleia flower will last because it depends on where in the world you live and what your climate is like but over here (England), Buddleia flowers are the showiest around the late summer and they can last for around 6 weeks. In the UK, the shrubs can grow up to 12 feet tall but will typically be about three or four feet high if grown in a pot. The bright, tubular flowers come in shades of blue, pink, purple and white with red throats that attract hummingbirds and butterflies for nectar as well as bees for pollen.

These blossoms last on the plant from a couple of weeks to a couple of months depending on the conditions.

What to Do Buddleia Butterfly Bushes After Flowering?

Once you have finished admiring the beauty of your buddleia and the blooms begin to fade it is time to start deadheading which will make your flowers last much longer. Deadheading is a gentle pruning to remove spent flowers to help promote new growth. As the flowers begin to fade, take your clean, sharp secateurs and cut below the flowerhead but above any new shoots that may have appeared. Continue to do this as each flower fades and you should have a beautiful Buddleia in bloom through to the autumn.

Deadheading is important, not only for promoting new growth but to prevent the plant from expending energy going to seed. Also, being invasive, you don’t want Buddleia spreading their seeds all over.

Overgrown Buddleia Butterfly Bush
Overgrown Buddleia Butterfly Bush

How to Prune a Buddleia

As opposed to deadheading after flowering, you will need to hard prune your Buddleia each year. This is best done after the last frost in your area which is usually around the time the plant has begun to show new growth. Buddleia can be susceptible to extreme cold once pruned so you will want to check the forecast and make sure that the cold has passed.

What You Need

  • Clean, Sharp Secateurs or Loppers
  • Gloves

Step 1 – Cut Back the Thick Woody Stems

Okay, now this is the part that you may feel is a little drastic, but I assure you that this is the correct way to do it. Using your loppers or secateurs, cut back all of the woody stems to around 45cm tall, just above the newest leaf node or a sign of fresh growth. Yes, that is right, all the way down to almost nothing even if there is new growth appearing above the cut. Just remember, once you have finished up your pruning, the Buddleia will resemble a stag’s antlers.

Also, remove any thin and weak-looking wood from the previous years’ growth – these can be pruned back to the ground.

Step 2 – Mulch

Now is the best time to add a few centimetres of compost or mulch to help the soil retain moisture once the rains have begun to subside.

Step 3 – Water

Buddleias are drought tolerant and as such do not require frequent watering for them to thrive. They will need watering during the spring when growth is at its strongest but not so much that the roots are constantly sitting in water as this will damage the plant. The soil should be moist, not soaking wet. In the summer, Buddleia will only need occasional watering – a good indication of this is when you see the leaves begin to curl and wither so if you see this, your plant may need a good, deep soaking.

Hard Pruning a Buddleia

How to Prune Buddleia in Containers

Buddleia in containers can be treated the same as if they were in the soil. After the last frost, cut right back into the old wood above the newest shoot about 45cm tall. As Buddleia flower on new growth every year, do not worry if you take your Buddleia down to almost nothing as it will come back stronger than ever.

Does My Buddleia Need to be Brought Inside for Winter?

A Buddleia that is in the ground will be fine with a little mulch but very small Buddleia in tubs, need protection and they should probably be brought indoors although if that is not an option – cut back the shoots slightly and then wrap the crown in a winter fleece (Amazon link – opens in a new tab) and that should prevent the worst.

How do you Propagate Buddleia Cuttings?

Given the uncontrollable spontaneous sowing of the butterfly bush, it is very rare that you need to start it yourself, but buddleia cultivars are easiest to propagate by cuttings in late spring. The semi-woody shoot tips usually root without any problems. If you missed the time, you could propagate the buddleia in the fall with cuttings but keep them indoors until spring.

Buddleia Pests and Diseases

All types of buddleias are very robust and are rarely attacked by diseases or pests. Spider mites can occasionally occur in warm, air-dry locations (their presence is indicated by light to silvery dots on the leaves). Powdery mildew can also occur in humid summers.

Are Buddleia a Tree?

No, buddleia (commonly known as butterfly bush) is not a tree. It is a deciduous shrub. However, with specific pruning techniques, buddleia can be trained to resemble a small tree or “standard” form, where it has a single main stem or trunk with a rounded canopy on top. In its natural form, buddleia grows as a multi-stemmed shrub with arching branches.

How to Train a Buddleia to Look Like Tree?

Training a buddleia (or butterfly bush) to look like a tree, often referred to as a “standard,” involves careful pruning and maintenance.

Buddleia Pruned into a Tree
Buddleia Pruned into a Tree

Here’s a step-by-step guide for how to make a buddleia tree:

  1. Choose the Right Plant: Start with a young buddleia plant. It’s easier to train a young plant than to reshape an older, established shrub.
  2. Select a Strong Leader: Identify the strongest, central stem to be the main trunk of your tree. This will be the “leader.”
  3. Prune Away Competing Stems: Remove all other stems at the base of the plant, leaving only the central leader. This encourages the plant to put its energy into growing upwards.
  4. Determine Height: Decide how tall you want the trunk of your tree to be. This will be the height at which the main canopy of branches will start.
  5. Prune the Leader: As the leader grows, prune away any side shoots or branches that form below your desired canopy height. This will ensure that all the growth and foliage remain at the top of the plant.
  6. Support the Leader: As the buddleia grows taller, it might need support. Use a stake to help keep the central leader straight, especially in windy conditions. Tie the leader to the stake using soft ties, ensuring not to tie it too tightly.
  7. Shape the Canopy: Once the leader reaches your desired height, you can start to encourage branching to form the canopy. To do this, pinch or cut out the tip of the leader. This will encourage side branches to grow, which you can then shape into a rounded canopy.
  8. Ongoing Maintenance: Each year, in late winter or early spring, prune the canopy to maintain its shape and remove any dead or damaged wood. Also, check the main trunk and remove any shoots that may appear below the canopy.
  9. Monitor Health: Ensure the buddleia receives adequate water, especially in the first couple of years. Feed with a balanced fertilizer in the spring.
  10. Protection: In areas with harsh winters, consider protecting the buddleia tree with a layer of mulch around its base.

Conclusion

Buddleia is a beautiful addition to any garden. With their bright, tubular flowers in a variety of colours that attract butterflies. They can be grown either in the ground or in containers, but both require hard pruning in the spring to maintain their shape and promote new growth. After flowering, deadheading your Buddleia is important not only for promoting the growth of new flowers to extend the blooming season but it is also important for preventing Buddleia from expending its energy on seed production.

5 Tips for Pruning Buddleia Infographic
5 Tips for Pruning Buddleia Infographic

Garden Doctor Tips

“Do not be afraid to prune your Buddleia hard – this promotes new growth, and your Buddleia will grow vigorously!”

“Check the weather forecast before you embark on your spring hard pruning, Buddleia can be prone to shock from colder temperatures!”

“Always deadhead your Buddleia as soon as the blooms begin to fade, this will extend the blooming season and prevent the production of seeds!”

“Do not overwater your Buddleia, make sure that the soil is moist and not soaking wet – unless they require a deep soaking in drought conditions!”

Frequently Asked Questions

Should I mulch Buddleia?

Adding mulch around your Buddleia is a good idea to prevent weeds from popping up and competing with your plant. Mulching also helps the soil retain moisture, if your buddleia is growing in more of a clay type soil, mulching probably isn’t required.

What kind of soil does buddleia need?

Buddleia grows best in loose, well-draining soil.

What time of year do you cut back butterfly bushes?

Buddleia should be cut back (hard pruned) in the spring just after the last frost. The only pruning you should do to your Buddleia in the summer months is deadheading to promote new growth and prevent seed production.

Should I Deadhead buddleia?

Yes, spent flowers should be removed as they have begun to fade. This is important to extend the blooming season so the plant can grow fresh flowers and not use its energy on creating seeds.

Should butterfly bushes be cut back for winter?

No. Buddleia should not be cut back for winter. Buddleia should be hard pruned after the last frost of the year as new shoots have begun to emerge. Pruning hard for the winter could be extremely detrimental to your plant.

Where did Buddleia get its name?

The butterfly shrub (Buddleia syn. Buddleja) or butterfly bush, also known as summer lilac, was thus named in honour of the English doctor, and amateur botanist, Adam Buddle (1660-1715). The most widespread of the Buddleia in gardens as well as in uncultivated or fallow areas, was discovered in 1869 in western and central China by Abbé David, who gave it his name: Buddleia davidii.

What colours do buddleias come in?

Depending on the variety, the flowers of the buddleia can be pink, light pink, white, lilac or dark purple.

What can you fertilise buddleia with?

In the garden, buddleia does not need to be fertilised. The situation is different with buddleia, which is kept as a container plant. This should be fertilised about every two weeks with a common tub plant or balcony fertiliser. Make sure that the fertiliser does not contain too much nitrogen, but enough phosphate.

How often do you have to water buddleia?

In the garden, buddleia does not need to be watered regularly. In the pot, on the other hand, the shrub should be watered regularly. Allow the surface of the soil to dry out from time to time. The moisture content can be easily determined with the finger test. It is important to avoid waterlogging.

When can you prune buddleia?

Every year, at the end of winter, after the last frost, the Buddleia davidii must be pruned severely by cutting back the clumps up to 20 cm from the ground, so that the vigorous branches can leave and offer abundant flowering the following summer.

How fast does buddleia grow?

Depending on the species, buddleia can grow up to two meters per year.

How tall does buddleia grow?

Depending on the variety, the height of the buddleia can be between 100 and 400 centimetres.

What goes well with buddleia?

Buddleia can be combined well with summer or late summer perennials such as asters or the stonecrop or when it is accompanied by other shrubs such as weigelia, hibiscus or tamarix which are also popular with butterflies.

Can you prune buddleia in autumn UK?

Yes, you can prune Buddleia (Butterfly Bush) in the UK during autumn, but it’s generally recommended to do light pruning in autumn to remove spent flowers and heavy pruning in late winter or early spring to promote vigorous new growth and flowering. Autumn pruning should be minimal to avoid stimulating new growth that could be damaged by winter frosts.


Author

Trevor Wright is not just a seasoned horticulturist; he’s the esteemed Garden Doctor. With a BSc in Horticulture and years of hands-on experience in the soil, Trevor has become a trusted mentor for all things gardening. As the founder of Garden Doctor, he’s committed to clarifying the intricacies of gardening, offering straightforward advice that’s rooted in years of practice. His writing is a garden of how-tos, savvy insights, and comprehensive guides that enable individuals to nurture and grow their garden dreams. When he’s not knee-deep in garden beds, Trevor is at his keyboard passing on his green-thumbed wisdom to budding gardeners, ensuring that the legacy of sustainable and joyful gardening blossoms far and wide.


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