Tall stems topped with globes of purple or white trumpets make agapanthus one of the great sights of late summer. The flowers last for weeks, bees love them, and the seedheads that follow add structure well into autumn.
We grow both a purple and a white form on our Lincolnshire farm, and the advice here applies to the hardy deciduous types that suit most UK gardens. You will learn how to choose a spot, plant in borders or pots, feed for flowers and keep plants safe through a cold, wet winter.
Agapanthus, African lily at a glance
- Botanical name Agapanthus, hardy deciduous hybrids, many derived from Agapanthus campanulatus
- Common name African lily, lily of the Nile
- Plant type Clump-forming herbaceous perennial with fleshy roots
- Hardiness Typically RHS H5 for deciduous cultivars (-10 to -15°C), evergreen types are generally less hardy
- Height and spread Around 60cm to 1.2m tall in flower depending on variety, spreading 45 to 60cm
- Flowering Rounded heads of trumpet-shaped flowers in shades of blue, violet-purple or white, July to September
- Foliage Narrow, strap-shaped green leaves that yellow and die back in autumn on deciduous types
- Position Full sun, ideally sheltered
- Soil Free-draining, reasonably fertile soil that stays moist in summer but never waterlogged in winter
- Good for Pots and patios, sunny borders, gravel and coastal gardens, cut flowers, bees
Deciduous or evergreen, and why it matters
Agapanthus fall into two broad groups. Deciduous types lose their leaves in autumn and rest underground, which makes them much more cold-tolerant, with most rated RHS H5 and coping with frosts down to around -10 to -15°C.
Evergreen types, derived from Agapanthus africanus and A. praecox, keep their broad leaves all year and are generally more tender. In colder inland areas they are best grown in pots and moved under cover for winter. If you are unsure which you have, watch what the leaves do in October.
Giving agapanthus the sunniest spot
Agapanthus come from southern Africa and flower best in full sun. A south or west-facing border, a spot against a warm wall or a sunny patio will give the most flower heads.
In shade they produce plenty of leaves but few blooms. They are well suited to the dry, bright conditions of eastern England and fit naturally into gravel gardens alongside other plants from our guide to the best drought-tolerant plants for UK gardens.
Planting in borders and containers
Plant in spring once the worst frosts are over, so roots have a full season to establish before winter. Drainage matters more than richness, as soggy winter soil is the main cause of losses.
- In the border, add grit to heavy clay and set the crown about 5cm below the surface.
- Space plants 30 to 45cm apart, or closer for a quick, dense display.
- In pots, use loam-based compost such as John Innes No. 3 with extra grit.
- Choose a container only slightly larger than the root ball, as snug roots encourage flowering.
- Raise pots on feet so excess water drains freely in winter.
Watering and feeding for more flowers
Water regularly from spring until flowering ends, especially plants in pots, which dry out quickly in summer. Border plants need help only in prolonged dry spells once established.
From spring until the buds show colour, give a high-potash liquid feed such as tomato fertiliser every two weeks. This builds up next year's flower buds as well as supporting this year's. Stop watering container plants almost entirely in winter while they are dormant.
Getting deciduous types through winter
In autumn, let the leaves yellow and die back naturally, then tidy them away. Cut faded flower stems to the base, or leave a few seedheads standing for winter interest and remove them in spring.
In the border, cover the crowns with a 5 to 8cm mulch of bark, straw or leaf mould in late autumn. Move potted plants against a sheltered house wall or into a cold greenhouse or shed, and wrap the pot in fleece or hessian during hard frosts so the roots do not freeze solid.
Dividing crowded clumps
Agapanthus flower best when slightly congested, so do not rush to divide. When a clump has filled its space or the pot is bursting, and flowering starts to drop off, it is time.
Divide in spring as new growth begins. The roots are thick and tough, so use two forks back to back or a sharp spade to split the clump, keeping several shoots on each piece. Divisions may take a year to settle before flowering well again.
Pests and problems to watch for
Agapanthus gall midge has spread through UK gardens since it was first recorded in 2014. Its larvae feed inside the flower buds, which become discoloured and distorted and fail to open. Remove and dispose of affected buds or whole flower heads promptly, and do not compost them.
Slugs and snails can damage young shoots in spring. Failure to flower is more often caused by too much shade, an oversized pot, too much nitrogen or recent division than by any pest.
Safety around pets and children
The RHS lists agapanthus as harmful if eaten by people, dogs or cats, and the sap can irritate skin. Wear gloves when dividing plants or cutting stems, and wash your hands afterwards.
Keep pets and young children from chewing the leaves or roots. If a pet eats part of the plant and seems unwell, contact your vet.
Planting ideas for purple and white forms
Purple agapanthus look rich beside golden grasses, yellow achillea or the silver foliage of lavender and santolina. White forms bring a cool, elegant feel and stand out in the evening light, especially near seating areas.
Mixing the two in a large pot or a sweep through a gravel bed creates a simple, classic scheme. Repeating clumps along a path gives rhythm in late summer when many borders are fading.
Questions about Agapanthus, African lily
Why is my agapanthus not flowering?
Shade, a pot that is too large, too much nitrogen or recent division are the most common reasons. Move it to full sun, feed with high-potash fertiliser in spring and summer and give it time to fill its space.
Can agapanthus stay outside in winter in the UK?
Hardy deciduous types usually survive outdoors in the ground with a thick mulch over the crown, especially in well-drained soil. Pots are more vulnerable because roots can freeze, so shelter them against a wall or under cover.
Should I cut back agapanthus in autumn?
On deciduous types, remove the leaves once they have yellowed and died back. Flower stems can be cut to the base after flowering or left for their seedheads until spring.
Do agapanthus like to be pot bound?
They flower best when the roots are fairly snug. Move them to a pot only slightly larger each time, and divide when the clump becomes so packed that the container is splitting or flowering declines.
With sun, sharp drainage and a little winter shelter, agapanthus will flower reliably for many years. Explore our perennials collection to find partners for your purple and white forms.