Agapanthus are notorious for being finicky plants, but the key to reliable flowering is understanding what they need to grow and bloom. Discover the secret to growing strong plants that produce stunning flowers every year.
Agapanthus are some of the most spectacular late summer flowers, with clusters of trumpet-shaped flowers perched on top of sturdy stems. They look wonderful grown in pots or planted in a sunny border, where they'll attract bees and other pollinators. Agapanthus has a reputation for being coy with its flowers. Follow the tips below to help your plants give their best and enjoy beautiful blooms in summer and early autumn.
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1. Plant agapanthus in full sun
Agapanthus are native to South Africa, where they enjoy long, hot, sunny days. To grow agapanthus successfully, you must plant it in full sun. If your agapanthus has weak, leggy stems and few flowers, it most likely needs more sun. While it may be tempting to move plants grown in pots to an out-of-the-way corner as the flowers fade, agapanthus still needs to be kept in a sunny spot throughout late summer and early autumn, as this is when flower buds form for the following year.
To encourage your agapanthus to produce the best flowers, make sure it gets at least six hours of direct sunlight a day, ideally more. If you don't have a suitably sunny spot, then save yourself a lot of frustration and plant flowers that thrive in partial or full shade instead.
2. Choose the right sized container
Agapanthus are excellent flowers to grow in pots, as they flower best when their roots are restricted. If a young plant is potted into a large container, it will put all its energy into growing roots, not flower buds. This is a common reason why an agapanthus plant may flower in the first summer after you buy it, but then fail to flower the following year. The flower buds on your new plant will have formed the previous year, when the plant was in a small pot; once these flowers are spent, the agapanthus then focuses on growing roots.
Some gardeners go too far the other way and leave their agapanthus in a small pot for too many years, then wonder why it stops producing flowers. While agapanthus do like their roots to be restricted, they don't like to be pot-bound, so it is important to repot larger plants into new containers every few years.
To make sure your agapanthus flowers every year, move up one pot size at a time, making sure the roots of the plant take up at least two-thirds of the space in the new pot. Planting three plants in a large container (for example, a 45 cm pot) is a good solution for young plants, which can later be separated into individual pots or combined in a larger container. Plants in larger pots suffer less during droughts and are also less likely to suffer frost damage over winter.
3. Water agapanthus regularly
Although agapanthus love the sun, they are not drought tolerant plants. In their native environment, agapanthus plants get plenty of water, even during summer, and they need consistently moist, well-drained soil throughout the growing season to thrive.
You'll need to water newly planted agapanthus and plants grown in pots regularly, particularly during heatwaves when compost in containers can dry out in a matter of hours. Plants grown in borders are more resilient, but will still benefit from watering during dry spells.
It's important to continue watering agapanthus during late summer droughts, as if the plant doesn't get enough moisture during this time, it affects the formation of flower buds, meaning you'll get fewer flowers the following year.
4. Feed regularly for more flowers
Agapanthus grown in containers will quickly burn through the nutrients in the compost. To keep your plants strong and blooming, feed every two weeks from spring to early autumn with liquid tomato feed or comfrey feed.
Agapanthus in borders don't always need feeding, but if your soil is poor or you want to give them a boost, use a rose fertiliser in spring and summer. Avoid feeding plants with high nitrogen fertilisers as this encourages leafy growth rather than flowers.
5. Deadhead agapanthus flowers
When left to nature, agapanthus flowers form attractive seedheads which add architectural interest to borders and pots throughout the autumn and winter months. However, if your priority is spectacular flowers, it's better to remove flowers by cutting the stalks at their base before they have a chance to set seed. This won't affect the number of blooms you get this year, but deadheading agapanthus flowers ensures that the plant puts its energy into forming flower buds for the following year rather than producing seeds.
Bonus tip! Protect plants from cold, wet winters
Agapanthus struggle in cold, wet soils, so you may need to take extra steps to keep plants alive over winter. Evergreen agapanthus are the most tender, and these are best kept in a frost-free greenhouse from late autumn to mid spring unless your garden has a sheltered, mild microclimate. Deciduous agapanthus (those that die back over winter) are hardier and better suited to growing in borders. You can give plants extra protection against cold winters by applying a 15–20 cm layer of compost, chipped bark, sand or straw around the plants in late autumn.
If you're growing agapanthus in pots and you don't have a greenhouse to put them in over the winter, move the pots to a sheltered location, either under cover or in the rain shadow of a south-facing wall or fence, and raise the containers on pot feet or bricks. This will help prevent the compost from becoming waterlogged. Wrap containers in bubble wrap or hessian to protect the roots from frost damage, and cover evergreen agapanthus with horticultural fleece during cold snaps.
Helping your agapanthus plants survive the winter without damage means they'll start off the growing season healthy and strong. And strong plants produce the best flowers!
