Agapanthus are some of the most striking summer perennials, with large, spherical clusters of trumpet-shaped flowers. The brilliant blue flowers are top of many gardeners' lists, but there are also soft purple, pink and white varieties. Find out how to look after these sun-loving plants in this care guide.
Agapanthus (African lily or lily of the Nile) are flowering perennial plants that produce clusters of vibrant flowers in shades of blue, purple or white. They flower from July to September and look best planted in sunny borders or large terracotta pots. Agapanthus are easy to grow but don't always flower as well as you'd like. If you're struggling, read our top tips to grow beautiful agapanthus flowers.
Agapanthus can be deciduous (where the foliage dies back over winter) or evergreen. They originate from South Africa, where they grow in two different climatic regions. Deciduous varieties are more hardy and are accustomed to dry, cool winters and warm, wet summers. Evergreen agapanthus are used to hot, dry summers and mild winters, so they may struggle outside in colder parts of the UK.
Where to plant agapanthus
Agapanthus needs plenty of sun to flower well, so make sure you plant it in a full sun or partially shaded location where it will get at least six hours of sun a day. They're not particularly fussy when it comes to soil type, and you can grow them in chalky or sandy soils, but make sure water drains through the ground, particularly in winter. If your garden has heavy clay soil, I'd suggest planting agapanthus in a raised bed or pots.
Agapanthus vary in size from around half a metre to a metre and a half (when in flower), so make sure you choose a variety that'll suit the space you have available. Agapanthus 'Golden Drop' is one of the most compact varieties for the front of a border, whereas Agapanthus 'Northern Star' will suit a mid to back border position.
Most agapanthus can be grown in pots, and they often grow better when their roots are restricted. Pots are also easier to move undercover or to a sheltered area in winter. Terracotta pots offer a lovely visual contrast to the blue flowers and are a practical choice for these heat-loving plants.
When to plant agapanthus
Mid to late spring is the ideal time to plant agapanthus in beds and borders, as this gives the plants a full summer to become established before the weather turns cold and wet. However, buying agapanthus plants in late summer or autumn allows you to see them in bloom (so you'll know they will flower!). If you're worried about planting agapanthus out in the garden at this time of year, plant them in a pot and keep them under cover over winter.
How to plant agapanthus
Before planting agapanthus plants, consider if you need to improve the soil. Agapanthus need well-drained soil, but they also need nutrients to flower well, so if your soil is very thin, dig in some compost, leaf mulch or other organic matter. If you have clay soil, then add grit or create a raised bed to help with drainage.
Dig a hole large enough to encompass the pot your agapanthus came in and carefully remove the plant from its pot. Place it in the hole and backfill the soil so the crown of the plant is just below the surface. Water it in well.
How to grow agapanthus in pots
Planting agapanthus in pots is one of the best ways to ensure it flowers well, but you need to use the correct size container. It's best to use a large pot and plant several agapanthus together rather than planting a single plant surrounded by compost, as if agapanthus has too much space, it will put all its energy into filling the pot rather than producing flowers.
Make sure your pot has drainage holes and part fill it with a mix of peat-free compost with added John Innes and grit (around 20–30% grit). Nestle your agapanthus plants in the pot and fill the remaining space with your compost mix. Water the plants well and place the container in a sunny position.
How to care for agapanthus
Agapanthus like well-drained soil, but to flower well, they also need moisture during the growing season. Young plants need regular watering for the first year, and more established plants may need watering during long dry spells. Even in later summer, plants may need additional water, as this is when they develop flower buds for the following year.
Agapanthus in pots will need more regular watering during the growing season to keep the compost moist. Avoid watering them too much in winter, and move pots to a sheltered area so the compost doesn't become waterlogged in heavy rain. Apply a liquid feed, such as tomato feed, to container-grown plants every two or three weeks from April to September.
Deadhead agapanthus flowers as they start to fade. Cut the stalks at the base rather than snipping off the heads. At the end of the season, you can let flowers develop into seedheads for autumn interest or deadhead them to encourage the plant to conserve its energy.
Agapanthus vary in how hardy they are. Most of the varieties we sell are rated to H4, which means they can cope with winter temperatures down to around -10°C, but some are borderline hardy. Even the hardier varieties will struggle with wet, cold soils in winter, so it's worth taking some simple steps to protect them, particularly if you live in northern England or Scotland.
If you're growing agapanthus in containers, move them into a frost-free greenhouse or up against a south-facing wall or fence to give them shelter from heavy rain. Wrap pots in bubble wrap or hessian to protect the roots from hard frosts and cover the plants with horticultural fleece if conditions are very cold. Add a thick (15–20 cm) layer of mulch, such as chipped bark, sand or straw, around agapanthus plants in beds and borders in late autumn.
How to propagate agapanthus
You can lift and divide mature agapanthus clumps every four or five years to get new plants. Each division will be identical to the parent plant. Divide agapanthus plants in spring to reduce the risk of the cut roots rotting over winter. Remove pot-bound plants from containers or lift plants grown in beds and use a sharp knife to divide the agapanthus plant into large chunks. If you're struggling to get a large agapanthus out of the ground, you can also dig around it and remove sections by hand.
When replanting agapanthus divisions in pots, you may need to choose a smaller pot than the original so there isn't too much space around the roots.
Agapanthus don't love root disturbance, and they may take a year or two to recover from being divided, so don't panic if they don't flower during this time. Once they've settled into their new home, they should start flowering as normal.
You can grow agapanthus from seed, though these plants will be hybrids and look different from the parent plant. Collect seeds in autumn, when the flowerheads turn brown and release the seeds. Dry and store agapanthus seeds over winter, then sow them shallowly under cover in March or April. It can take three or four years for plants grown from seed to flower, so you'll need to be patient!
Common problems
If your agapanthus is not blooming as well as you'd like, you're not alone! This is a common problem with agapanthus, and it could be due to the plants not getting enough sun or water, or being in the wrong sized pot. Check out this detailed guide to troubleshoot why your agapanthus isn't flowering.
Agapanthus gall midge can cause flower buds to deform and fail to open. If you think your agapanthus plants are affected, open an affected flower bud and check if there are any tiny cream coloured maggots inside. Remove and destroy affected flowerheads. If the plant is in a pot, repot it with fresh compost to remove any larvae in the soil.
Our favourite agapanthus varieties
Agapanthus 'Fireworks' is an evergreen agapanthus with distinctive purple-throated white flowers. The flowers are larger than average and last an impressively long time. Agapanthus 'Twister' is a hardier variety with similar colouring.
Agapanthus 'Northern Star' has striking violet-blue flowers with a deep purple stripe down each petal. It grows up to a metre when in flower and holds the RHS Award of Garden Merit.
Agapanthus 'Poppin' Purple' is a repeat blooming variety that often produces a second flush of flowers in late summer. It's fast growing and produces violet flowers that open from deep purple buds.
Agapanthus 'Brilliant Blue' has dazzling blue flowers that perch on top of sturdy stems. A more compact variety that looks good at the front of borders as well as in pots.
Agapanthus 'Arctic Star' is a lovely white agapanthus with dark grey-green leaves. A hardy, elegant variety well suited to contemporary gardens.
FAQ
When do agapanthus flower?
Agapanthus flowers from July to September in the UK. Some varieties bloom in a single burst of colour that lasts up to six weeks, while others, such as Agapanthus 'Poppin' Purple', have been bred to flower repeatedly over a longer period.
Do agapanthus spread?
Agapanthus plants grow into large clumps, but their roots aren't invasive and they won't take over your garden. You can divide mature clumps every four or five years. Agapanthus seedlings may also grow from seeds dispersed naturally in late summer or autumn. To prevent this, deadhead agapanthus flowers before they have a chance to set seed.
Do you deadhead agapanthus?
Cut individual agapanthus flower stalks at the base as the flowers fade. You may wish to leave some flowers on at the end of the summer to turn into seedheads for added interest in autumn and winter, but deadheading the flowers prevents seeds from spreading and focuses the plant's energy on producing flower buds for the following year.
How do I plant agapanthus?
Agapanthus likes plenty of sun and well-drained soil. You can plant agapanthus in sunny borders or in pots. Add some grit to heavier soils before planting and dig a hole a little larger than the pot your plant arrived in. Plant your agapanthus plant at the same depth it was in the pot, with the crown just below the surface. When planting agapanthus in pots, choose a container only a little larger than its current pot, or plant three plants together in a larger container.
