If you have a deciduous Agapanthus that you plan to keep outdoors over the winter months, then it is usual to cut back the stalks with spent flowers or seed heads (if these have not already been deadheaded) to around 10cm above the ground.
Evergreen varieties – Evergreen agapanthus varieties require no cutting back. However, you can trim both evergreen and deciduous plants as needed to remove dead, damaged or unsightly growth.
Agapanthus are perennials which means they come back each year. Most are hardy, and their leaves will die back each winter before returning in the spring. Evergreen types tend to be more tender, so will need some protection in the winter and early spring.
Snip off the spent blooms before they go to seed with sharp and clean secateurs, cutting off the stalks close to the base of the plant to keep things neat. Place the dead flower heads into your composting system.
“Agapanthus stems can be pruned at ground level when the flower has gone over unless you want to leave them in the garden for winter structure,” says Patrick Fairweather, the Managing Director of Fairweather's Nursery. “Flower stems should also be removed from young plants to encourage root and shoot development.”
Agapanthus pruning is also essential to encourage healthy growth. You can do this after the flowering season, cutting back the stems to around 10 cm above ground level for deciduous varieties, which include Agapanthus Melbourne, Agapanthus Galaxy White, and Agapanthus Little Galaxy.
It is a perennial plant that can live for up to 75 years. Its evergreen leaves are 2 cm wide and 50 cm long. Its inflorescence is an umbel. The flowers are blue, purple or white and bloom from late spring to summer, followed by capsules filled with black seeds.
You can prune agapanthus at any time of year to remove dead, damaged or diseased foliage. For deciduous varieties, spent foliage can be removed in late fall, but this will leave the crown exposed to the winter elements. Never remove foliage after blooming as this deprives the plant of the energy it needs to overwinter.
Dividing and transplanting agapanthus
However, if left untouched for any length of time, they will become overcrowded and may flower poorly. Lifting and dividing agapanthus every 3 to 4 years will promote better flowering.
This plant can be easily propagated through division in late autumn to winter by carefully removing it from the ground or the pot. Gently shake off some of the soil so that you can see the roots and the individual plants. Carefully pull the individual plants apart making sure that each one retains its own roots.
The Agapanthus plant leaves will turn yellow when put under direct light of very high intensity. Provide some shade for them during the afternoon hours at least. Overwatering will also turn the leaves of this plant yellow, soggy and plump.
The best time to divide your Agapanthus is in the spring or early summer as soon as you notice the new shoots emerging or alternatively in the autumn. We would personally recommend the middle of September or October once your plants have finished flowering.
Agapanthus grows and spreads by fleshy rhizomes that act as storage roots. The plant retains nutrients in its roots and may be divided to create more plants. Use a sharp shovel to dig up an established plant and divide it into several sections, each with roots and foliage.
They do not actually change colour but as the seeds germinate under the mother plant, seedling variation means these new plants could be white or blue! Once again, simply pruning the finished heads will stop the seed forming and ensure your aggies stay the colour you planted.
With thick, sturdy stems, Agapanthus make excellent cut flowers. The stems provide a strong vertical element to floral designs, while the flowers themselves are open and airy. Gather stems, cutting near the base, when several flowers in the cluster have opened. The remaining closed buds will open indoors in the vase.
“Agapanthus are an extremely tough species and can grow a new plant from just a tiny section of an underground rhizome,” she said. “They can even withstand very intense commercial-grade composting.”
Agapanthus is one of those bulbs that does not like or need to be divided frequently. They actually like to be crowded and bloom best when left alone. But when a clump becomes too large for an area, separating is a useful way to reduce its size.
It is important to pull out all roots from beneath the soil. Alternatively, cut the flower heads off before seeding to help prevent spreading. Brush cutting or mowing must be done regularly.
To restrict its spread from your garden, deadhead stalks as flowers finish and don't dump unwanted plants. If you have a mass planting of agapanthus, deadheading sounds onerous, particularly for a plant that's often grown for its low maintenance.
Ensure that the whole rhizome is removed. Slash leaves close to the ground and paint the fresh stump with vigilant gel, glyphosate, or metsulfuron-methyl. Spray with triclopyr.
Agapanthus are very easy to propagate by division. Lift the bulbs in spring while dormant or, in the autumn, after flowering, and gently remove the smaller offshoot bulbs. If the clump is ancient and far too large to handle easily a spade can be used to split it up for replanting elsewhere.