Growing a butterfly bush in a pot

Which varieties to choose?

There are around a hundred species and nearly 300 cultivars in the Buddleia family. For pot cultivation, opt for compact varieties that reach between 50 cm and 1.5 m at maturity. These varieties are perfect for small sunny spaces.

Among them:

• The Buddleia Bloomtastic ‘Dreaming Lavender’: this 50 cm high bush with a prostrate to trailing habit makes a striking impact in a pot!
• The Buddleia davidii ‘Sophie’: a very compact variety that does not exceed 60 cm in height and 80 cm in width. Its beautifully trailing branches add a lot of charm to a pot!
• The Buddleia davidii ‘Nanho Blue’: its modest size, about 1.5 m in height with the same spread, is particularly suited to small spaces, offering lavender-blue panicles.
• The Buddleja ‘White Chip’: a dwarf and hardy buddleia of 90 cm in height that forms a lovely round bush adorned in summer with upright white flower spikes with an orange throat.
• The Buddleia ‘Blue Chip’: the blue version of the previous one! A dwarf and compact variety with a 1m spread and mauve-blue flowers.
• The Buddleja ‘Lilac Chip’: it forms a small prostrate bush of only 70 cm high, blooming all summer with lilac flowers on beautiful silver foliage.

→ check out our article “Which Buddleia or Butterfly Tree to Choose?” to help you select the one that suits you best.

Above, Buddleia Bloomtastic ‘Dreaming Lavender’, on the left the ‘Nanho Blue’ butterfly tree, and on the right the cultivar ‘White Chip’

What pot for the butterfly bush?

Buddleias are bushes. It is important to choose a container large enough for their root system to develop in a sufficient volume of soil, which is essential for optimal growth and generous flowering. Choose a pot 2 to 3 times larger than the size of the root ball. A container with a diameter of 40 to 50 cm should be suitable. Ensure that the container has drainage holes to allow excess watering or rainwater to escape. Opt for terracotta, which has the advantage of being porate and allows for better aeration of the substrate. Plastic pots are more manageable and lightweight but tend to retain moisture.

What substrate?

Not demanding regarding soil type, the Butterfly Tree is content with even mediocre soil in open ground. It appreciates ordinary soil, even calcareous, as long as it is well-drained. To improve this drainage, you should lay a bed of gravel or clay balls at the bottom of the pot. In pots, nutrient reserves diminish quickly, so the substrate should be a bit richer. If you have a garden, make a balanced mix of ordinary compost with garden soil, then add a handful of planting sand or vermiculite. Otherwise, make a mix of potting compost and sand.

Drainage, essential for pot planting

→ To learn all about substrates, check out our article: «Balcony, terrace and small gardens: composts and fertilisers perfect for small spaces – The latest innovations»

When and how to plant a buddleia in a pot?

The planting of Buddleia in pots or containers is done in spring, in March-April.

Steps for Successful Planting

• Soak the root ball in water for about ten minutes
• At the bottom of the large perforated container, place a layer of clay balls, pumice, or gravel (about 20% of the pot’s volume)
• Cover with part of the mix up to halfway of the pot
• Install the Buddleia, with the top of the root ball a few centimetres below the rim of the pot
• Fill in with the rest of the mix
• Gently firm the soil around the base by hand
• Water
• Spread an organic mulch to prevent the substrate from drying out too quickly

What exposure for a buddleia in a pot?

In the sun, sheltered from strong winds, as it requires full sun to flower well. Very resistant to pollution, the Butterfly tree thrives in the city, making it an ideal plant for small urban gardens, well-exposed romantic terraces, or sunny balconies. In the southern regions of France, cultivation in partial shade is possible, but flowering may be less abundant. It also adapts well in seaside gardens as it withstands sea spray.

The butterfly tree needs sun to provide its generous flowering

What care does potted Buddleia need?

Watering the Buddleia in a Pot

The Butterfly Bush is incredibly robust, tolerating both cold and drought. However, in a pot, it will need to be watered more regularly, as the substrate dries out faster than in the ground.

• In summer: water twice a week when the soil is dry, spacing out the waterings, and very little in winter. Applying a mulch at the base of the bush will help keep the soil moist in summer.
• In winter: reduce watering to once every two weeks in the absence of rain.

Fertilisation

In pots, nutrient reserves deplete quickly, and the substrate exhausts more rapidly than in the ground. To stimulate flowering, your bush will appreciate once a year in spring a few handfuls of organic fertiliser (decomposed manure, compost, horn, etc.).

Pruning

The Buddleia flowers on the wood of the year. Do not hesitate to prune it to maintain a nice compact habit and ensure it remains floriferous. This is even recommended since flowers appear on the shoots of the year. Prune every year in February-March, before the vegetation starts again. A good pruning at the beginning of spring maintains good proportions, a ramified habit, and encourages the bush to produce many flowers. You will not compromise the upcoming flowering; on the contrary, you will stimulate it!

1. Remove faded flowers as they occur during summer to encourage further blooming.
2. Using a pruning shear, cut all the previous year’s shoots to 10-15 cm above the old wood, above a pair of buds.
3. Severely cut back the branches starting from the base of the bush to 30-50 cm.
4. Remove weak shoots, dead wood, and poorly placed branches down to the ground.

⇒ Also read our advice sheet: “Buddleia, Butterfly Bush: How to Prune It Well”.

Prune your Buddleia in a pot at the end of winter

Wintering

Buddleias offer good hardiness and withstand cold very well, with some tolerating temperatures below -20°C. In pots, they can spend the winter outside and do not need to be wintered. However, it is advisable to protect young bushes grown in pots, as they are more sensitive to cold than those in the ground. If you live in an area with harsh winters, mulch the stump with a thick organic mulch and possibly insulate the pot with cardboard or bubble wrap to protect the roots from the cold.

Repotting

Repot your Buddleia into a larger container every 2 to 3 years at the end of winter to completely renew its substrate and provide new nutrients. In other years, you can simply perform a top dressing by replacing the exhausted substrate on the top few centimetres with fresh potting soil.

Pests and diseases

Buddleias are very resilient flowering bushes that have no significant enemies. In pots, they can, however, be more vulnerable than in the ground and may be attacked by bugs, caterpillars, otiorrhynchs and red spider mites.

For further reading

→ To learn all about Buddleias and their cultivation, discover our complete guide: “Buddleia, Butterfly Tree: planting, pruning, maintenance”