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12 March 2021

How to grow agapanthus

Agapanthus, or African lilies, have the sort of relaxed glamour that evokes memories of summer holidays in sunnier countries.
Agapanthus
CT
Ceri Thomas

Agapanthus are beautiful plants for a sunny borders and pots. They like well-drained soil. The deciduous kinds that lose their leaves in the autumn are hardier than evergreen ones so recommend you grow these.

Which? Gardening magazine grew a range of popular varieties to see which would give us the best display.

How to grow agapanthus: month by month

January February March April May June




PLANT PLANT/DIVIDE PLANT

July August September October November December
FLOWERING FLOWERING

MULCH



Best agapanthus varieties

Which? members can log in now to see the full results and which are our Best Buy varieties. If you’re not a member, join Which? to get instant access.

Best Buy agapanthus
What it looks like Variety name Height x spread
Member content
Member content
105 x 50cm
Blue is certainly the classic colour for agapanthus but some blues make more of an impact than others. These two were quite similar and easily as vibrant as each other. The flower stems of this variety were long, slim and slightly bendier than those of our other Best Buy, but held the flowers elegantly. We had a consistent and long-lasting display in the north and the south of the UK. Peak flowering: July to August.
What it looks like Variety name Height x spread
Member content
Member content
90 x 50cm
We soon knew that this was going to be a contender as the big clumps of wide leaves threw up numerous strong, thick flower stems. The large flower heads then opened with a vibrant display of dark-blue blooms on almost black flower stalks. They were about the most consistent and longest flowering in the trial in the north and the south of the UK, and every part of the plant was sturdy and strong, as well as elegantly proportioned and poised.  Peak flowering: July to August.

How we test agapanthus

We chose 21 varieties of deciduous agapanthus and,  in spring, planted three plants of each at our Which? Gardening magazine trial garden in North London and at Greenbank Garden on the outskirts of Glasgow. We grew and assessed them through two growing seasons for: the impact of the flowers, including how big and full the heads were, and how long they bloomed; how well they established and developed within two years; their attractiveness to pollinating insects; how susceptible they were to common problems.

Caring for your plants

Planting

Buy 1-2L-sized plants if possible. Plants in 9cm pots should be grown on in larger pots and protected in winter before planting out. 

Plant in spring so they establish before cold weather sets in. Position in well-drained soil in full sun.

Watering

Deciduous types grow in summer, so don’t let them dry out in spells of dry weather as this will affect flowering the following year. 

Protect plants from winter cold

Mulch plants with a layer of straw or fleece in late autumn to protect them from cold winter weather. Established plants should cope with colder conditions, but in very cold areas, mulching may improve flowering the following year.

Growing in pots

Agapanthus can grow well in large pots. Use a Best Buy compost for containers and mix in a Best Buy controlled-release feed. Remove the top few centimetres of old compost each spring and replace with fresh compost and feed.

Water regularly and feed with high potash feed, such as tomato feed, during the growing season.

Repot regularly to the next size up, as restricted roots lead to fewer flowers, not better flowering, as is often said.

Making new plants by dividing

Congested clumps can be divided and replanted in spring. Dig up the clump and pull it apart or cut into pieces with an old knife. Each piece needs to have roots and shoots. Replant the pieces straight away - any spares can be given away to family and friends.

Common growing problems

Agapanthus gall midge

This is a relatively new pest to the UK. The larvae attack flower buds leading to distortion and discolouration, and can be seen inside the bud. There are no chemical controls, but picking off the flower buds may help to reduce future damage.


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