The buddleia is known as a wonderful summer flowering shrub. It is even better known for the butterflies, to which he owes his second name butterfly bush. Hardly any ornamental shrub is able to attract so many butterflies to its blossoms.
Although Buddleia can be pruned to look like a tree, Buddleia is not considered a tree at all, it is a genus in the figwort family (Scrophlariacae) and it grows as deciduous, winter or evergreen subshrub or shrub.
One should not be misled by another of its common names ‘Summer lilac’; the Buddleia is not related to the real lilac (Syringa).
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.
Where does Buddleia Come From?
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).
Buddleia is common in the tropical and subtropical areas of America, Africa and Asia. There are around 100 species worldwide that grow primarily in full sun and hot locations on sometimes very dry and poor soil.
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. It was only sent to Europe in 1890 by the English botanist Auguste Henry, and from 1895, the Vilmorin nurseries cultivated it.
Today, its invasiveness concerns all of Western Europe as well as Australia and New Zealand!
What Does Buddleia Look Like?
From a horticultural point of view, the species called Buddleja davidii is particularly interesting. Numerous cultivated forms (the so-called Davidii hybrids) with different flower colours and growth heights are available.
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.
In mild winters, most of the previous year’s foliage often sticks to the shoots, and the leaves only die off and fall to the ground in severe frost. The large, elongated panicles of flowers stand at the ends of this year’s main and side shoots.
The flowers open from July and often bloom until the first frost. The varieties have white, light pink, rose-red and lilac to dark purple flowers.
At the end of flowering, we can observe the fruits: tiny brown capsules arranged in erect clusters, producing thousands of seeds that will germinate without complication as soon as they touch the ground.
Where to Plant Buddleia Tree?
The Butterfly Tree can adapt as much to light, healthy, even dry and stony soil in a sunny location. Other Buddleia species will also need full sun, sheltered from strong winds, and prefer deep, drained soil, although poor, chalky soil won’t bother them.
The planting distance depends on the variety-dependent growth form. Buddleias look best individually, for example in the middle of the meadow or planted with groundcover in a flat perennial bed.
In a group with other shrubs, the beautiful, arching growth comes into its own. It is advisable to give it enough space so that it can fully exploit its growth potential.
How to Transplant Buddleia Tree?
Every garden changes with time and the demands of the gardener. When starting a new project, sometimes there is a need to transplant a shrub or two.
Like when planting, transplanting is best done in spring and is best combined with pruning at the end of winter after the last frost. It is best to dig around a 30×30 area around the base of the bush with a spade and lift the plant by the root ball.
The plant can then be moved to the new location although for a longer transport, wrapping with a jute bag or a tarpaulin is recommended.
At the new location, the planting hole is dug much larger than the root ball. The ground needs to be loosened up with a digging fork. Loose soil facilitates subsequent growth and rooting.
Note: It is important to ensure that the root ball is preserved and does not fall apart.
How to Care for Buddleia?
The care of buddleia is quite simple and is similar to that of other ornamental shrubs. This includes watering during dry periods and mulching around the base with organic plant material or compost in early spring.
In normal winters, buddleia doesn’t need shelter. But severe frosts cause the shoots to freeze back to the base. To prevent these frostbites, the base of the shrub can be protected with fleece, pine needles or other dry mulch.
Buddleia in tubs, however, 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.
Note: As long as sufficient buds remain at the base even after harsh winters, there is no need to worry.
How do you Prune Buddleia Tree?
The buddleia only retains its beauty if it is pruned annually. The cold season leaves clear marks on the bush.
The buddleia is cut back heavily in the spring after the last frost because it only blooms on the new wood. This is an important measure to avoid mistakes when caring for the buddleia.
It is enough if you only leave two to four buds from last year’s flowering shoots. It then forms particularly strong new shoots with large blooms.
If you want to prevent the butterfly bush from self-seeding, you should cut off the withered blooms as they fade.
More You Might Like: What to do with Buddleia After Flowering
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.
The butterfly bush also does not grow true to the variety and usually has the purple flowers of the wild species.
For the multiplication of botanical species or cultivars true to the parent type, you will have to proceed by cutting semi-hardened stems at the end of summer: success is quite easy and with a little rooting compound, you will obtain plants identical to the parent.
What is the Use of Buddleia?
Butterfly bush is a low-maintenance shrub that grows to a manageable size, depending on the variety. It is ideal for smaller home gardens or as a background for late summer perennial beds. The ornamental shrub comes into its own when the surrounding perennials are no higher than one meter.
As the name suggests, the butterfly bush is a real butterfly magnet in the garden. Colourful butterflies such as the Lesser Tortoiseshell and the Peacock Butterfly are magically attracted to its nectar-rich, fragrant flowers.
At the same time, the plant is also a neophyte, which means that it continues to spread in nature. It is particularly dominant in dry locations: railway embankments and brownfield sites in inner-city areas are often densely overgrown with buddleia.
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.
Measuring 2 to 5 m in height, the Buddleia tree is not actually a tree at all but a shrub with angular, pubescent, arching and spreading branches. The deciduous leaves, oval, lanceolate, finely toothed, have the shape of a spearhead, they are dull dark green on the top and greyish-white tomentose on the reverse.
The buddleia, a woody pioneer species, has become invasive, outside the garden, in nature, and especially in vacant lots, along watercourses and on all unmaintained grounds: it ends up dominating and taking the place of plants that grew there naturally.
It is therefore advisable for the garden to monitor its expansion: by cutting the faded flowers to prevent them from ripening and the seeds from spreading, by pulling out the unwanted shrub or by cutting it at the base.
The butterfly bush is undemanding, it requires little or no watering and does well without fertiliser.
Garden Doctor Tips
“Plant your Buddleia in full sun!”
“To prevent going to seed, remove spent flowers as they fade!”
“For best results, give a hard pruning at the end of the summer or the start of spring!”
“To grow a buddleia the same as the parent, you will have to propagate from cuttings!”
Frequently Asked Questions
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.
When is the right time to plant buddleia?
Buddleia can be planted all year round, but spring and early summer plantings grow better, therefore, becoming established and well prepared for a cold winter.
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 do you prune buddleia?
When pruning Buddleia, all main branches are pruned back to finger-length pieces with a few pairs of eyes. Thin side shoots are completely removed.
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.