Dig up a clump, separate it into the desired number of divisions, and replant them back into other areas of the landscape or in pots. Dividing agapanthus does discourage blooming, and the smaller you make the divisions the longer it will take the plants to come back into bloom.
Established clumps can be lifted and divided into smaller clumps. Spring (late March and April) is the best time to do it. This is the best way to make more plants of a cultivar as all the new clumps will be exactly the same.
Every two or three years you need to dig up your agapanthus and divide them. You can tell they need dividing if they are flowering less over the summer as they maybe too cramped and need more space to shine.
The soil around the roots is carefully removed and with gentle pressure the offset breaks away cleanly from the main plant. Again when replanting do not water for a few days and keep the plants in a sheltered position. It will take about one month for the new roots to strongly emerge into the potting media.
Dividing agapanthus
The best time to divide agapanthus is late March to April, before the flowering season. Lift the plant out of the ground and split the root clump with a sharp spade or two forks back-to-back, making sure each of the new clumps has at least two growing points. Then simply plant these out as usual.
As the plants mature, they crowd against each other underground, and this overcrowding limits their flowering. The best way to remedy the problem is to start dividing and transplanting agapanthus.
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.
Deciduous varieties – Cut back agapanthus stems to about 4 inches (10 cm.) above the ground at the end of the blooming season. However, if you like the texture and structure that spent plants provide to the winter landscape, cutting back agapanthus can wait until early spring.
Generally 3-4 inches deep for the larger variety and about 2 inches for the dwarf varieties.
Pot-grown agapanthus will benefit from an annual feed – a liquid tomato feed is ideal. Deadhead spent blooms to encourage more to form, or leave the faded flower heads in place if you want to collect the seed. The attractive seedheads are often left on over autumn for decorative reasons.
To bloom regularly, fertilize agapanthus twice a year, either after blooming, in early fall (September in the Upstate, October in the Lowcountry), or in early spring (early March in the Lowcountry and April Upstate). A low-nitrogen, complete fertilizer that includes phosphorus is best, such as 5-10-15 or 8-8-8.
Plant 60cm apart for tall varieties, and 30cm for dwarf varieties with the plant crown at soil level. When planting in pots, root congestion is not a major concern, as Agapanthus plants tend to respond quite well to this. When the roots have too much space, leaf growth will be encouraged rather than flower production.
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.
“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.
Cut back the flower stems all the way to the base of the plant. Deadheading prevents the plant from going to seed and helps the plant store energy in the rhizome. If self-seeding is desired, allow a few blooms to produce seed and ripen on the stem.
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.
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.
Collect seed when the seedhead is becoming brown and the capsules are starting to burst. If the weather is turning cold you can collect seed prematurely and store the whole seedhead in a paper bag, but it's preferable to let the seed ripen on the plant.
Herbicide Sprays to Kill Agapanthus
Common recommendations are for glyphosate, metsulfuron-methyl (MSF600) and triclopyr (Triclo). Our experience is that they all will work, but that glyphosate and MSF600 are more effective at some times than at others.
A peat-free, loam-based potting mix, with some sand or grit added for drainage is ideal for growing Agapanthus.
Agapanthus roots are a good example of a plant with a good ability to withstand drought and poor growing conditions due to its large, fleshy roots.