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08 Mar 2024

How to grow buddleia and best varieties

Buddleia are incredibly popular in our gardens as they attract butterflies, bees and other pollinators. Find out which buddleia varieties are the best for your garden and tips on how to grow them.

Which?Editorial team

In this article

Key facts
How to grow buddleia: month by month
Best buddleia varieties
Full testing results for buddleia
Caring for your plants
Problems
How we test buddleia

Buddleia are incredibly popular with butterflies, bees and other pollinators, their spikes of tiny tubular flowers filled with rich nectar. But the plants are fast-growing and can soon outgrow their space. Recent breeding has developed dwarf varieties that should be ideal for smaller modern gardens and some that claim to be suitable for containers and hanging baskets.

To find the best buddleias to grow, Which? Gardening magazine grew a range of new dwarf varieties to see which would give us the best display of flowers and live up to their compact claims.

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Key facts

PLANT TYPE Shrub

POSITION Full sun or part shade

SOIL Any well-drained soil

How to grow buddleia: month by month

January	February	March	April	May	June
PLANT BARE-ROOT	PLANT BARE-ROOT/PRUNE	PLANT BARE-ROOT/ PRUNE
July	August	September	October	November	December
FLOWERING	FLOWERING	FLOWERING	PRUNE	PLANT BARE-ROOT	PLANT BARE-ROOT

Best buddleia varieties

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Full testing results for buddleia

Dwarf buddleia

Variety name	Overall rating	Height x spread (cm)	Flowering duration	Flowering impact	Compactness	Weather tolerance	Pest and disease tolerance
B. alternifolia 'Unique'
'Buzz Hot Raspberry'
'Buzz Velvet'
'Dreaming Purple'
'Flutterby Petite Dark Pink'
'Flutterby Petite Snow White'
'Lo and Behold Blue Chip'

OVERALL RATING The more stars the better. Rating ignores price and is based on: flowering duration 25%, flowering impact 25%, compactness 40%, weather tolerance 5% and disease resistance 5%. Figures given are from the second year of the trial. Height and spread taken at peak flowering in the second year of the trial. Eventual height and spread might be more.

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Caring for your plants

Planting

Buddleias are relatively unfussy and will grow on rocky ground, in walls and through paving. However, your plants will be more robust and flower well if planted in fertile soil in full sun.

Help your plants with a recommended soil improver

Growing in pots and baskets

Some dwarf varieties of buddleia, such as the Rocketstar series and ‘Dreaming Lavender’ are ideal for growing in containers; steer clear of the Buzz varieties which are still being sold as ‘patio buddleia’, but will grow too large for most pots. Be sure to balance the size of container with the expected size of the plant to prevent it looking top-heavy. Fill your container with a Best Buy compost for pots and add some controlled-release fertiliser at planting time.

Keep an eye on watering especially during hot dry conditions and deadhead regularly to keep the flowers coming. Refresh the compost each spring by removing the top layer and replacing it with fresh compost and some additional controlled-release feed.

Feeding and mulching

Feed plants in the ground in spring with a potassium-rich granular fertiliser, such as rose food. Mulch to keep the moisture in, but avoid coarse woody mulches that lock up nitrogen and starve the plant. Deadhead regularly during summer to keep the flowers coming.

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Pruning buddleia

For the best display of flowers, our trials showed that you should shorten all the branches to 45cm above soil level in early spring, pruning above an outward-facing bud, then cut all the branches back to 45cm again in May. Deadhead continually as the flowers fade Pruning to prevent wind rock is useful in gardens exposed to strong winds. Cut back from a third to half of the height of the plant in late autumn.

Problems

Buddleia are generally trouble free. Watch out for late frosts that can damage the emerging buds; waterlogged soil over winter can cause plants to fail.

Eelworms

Eelworms can be a problem in damp soil. These microscopic nematodes affect the leaves and buds causing curling and yellowing. Remove and destroy all affected shoots and leaves.

Downy mildew

Downy mildew may affect the leaves in damp summers; pick off and dispose of any affected foliage.

How we test buddleia

We planted three plants of each variety at the Which? Gardening magazine trial garden at Capel Manor College in north London; container and hanging basket varieties had controlled-release fertiliser added to the potting compost and were positioned in a sunny spot. We grew the plants for three years, deadheading as necessary and assessing them in the first and second years for flowering duration, how good a display they made and whether the plants had a compact habit suitable for small gardens or containers. The container-grown plants were top-dressed with fresh compost and controlled-release fertiliser in the first and second spring. All plants were pruned in the second spring.