Without deadheading, the plant goes to seed and the blooming season is shortened considerably. To deadhead agapanthus, simply use pruners or garden shears to remove the faded flower and the stalk at the base of the plant.
Once you have decided which flowers need to be removed, simply take a sharp, sterilized pair of secateurs and cut off the flowering stalk close to the base of the plant. It does not really matter where on each stalk you choose to make your cut.
Although agapanthus are the ultimate easy-case plant, you should take care to remove the finished flower heads. These are quick to seed and can often become a menace in suburbs adjoining bushland areas.
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.
The best time of year to cut back agapanthus is in early spring. Leaving the spent foliage over the winter can protect the crown from rot during winter rains and insulate the roots from cold temperatures. During the summer, you can help the plant conserve energy by removing spent flowers.
It is naturally disappointing when agapanthus don't flower well. It's quite a common problem, however, and thankfully one that can be resolved. To ensure a good display next year, keep plants well-watered through summer until early autumn, which will encourage the development of new flower buds.
Repeat flowering Agapanthus for up to 6 months of the year.
These gorgeous plants produce masses of bright and colourful flowers in spring and summer, as well as sporadically throughout the year, including in mild winters as seen in 2020.
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. They are easy to grow, preferably sown fresh and pricked out individually next spring. With a bit of luck they should come to flower the following season.
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.
NOTE: PeeGee and most other hydrangeas dry best if picked just as they're starting to turn pink. Seed heads from Black Eyed Susans, coneflowers, agapanthus, cattails, lunaria (money plant), iris, teasel, poppies, and Queen Anne's lace are also attractive in dried flower bouquets, as are stems from ornamental grasses.
Agapanthus thrive in full sun and need 6-8 hours of sunlight each day. However, they do better in partial shade in hot climate areas. Agapanthus perform best in fertile, moist and well-drained soil. They show no preference for pH, except Agapanthus africanus which prefers an acid soil.
Growing agapanthus
Give agapanthus lots of sun, plus extra water when its really hot and dry and they'll bloom abundantly. Agapanthus plants that fail to flower are usually growing in too much shade.
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.
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.
Because agapanthus plants spread quickly, they are regarded as an invasive weed in parts of New South Wales and Victoria. Your local council can provide guidance on growing agapanthus, which may include dead-heading flowers before seed dispersal.
The benefit of growing agapanthus in pots is that it's easy to bring the tender, evergreen types under cover in autumn, so they're protected from winter cold and damp. An unheated greenhouse or conservatory is ideal for over-wintering them. The more hardy deciduous types can be left outside.
Regarding your agapanthus plants, it could be a water problem; either too much or not enough. Too much water mimics the signs of not enough water. Soil that is too wet won't have enough air pockets and plants will not be able to breathe by taking up oxygen with their roots. How have you been watering?
Decorative Life: 6-14 days.
Agapanthus growing in containers should be moved into a frost-free but cool location before the first frosts in your area. An unheated greenhouse or polytunnel is ideal, but a very sheltered spot at the base of a wall may also work in some areas and for some types of Agapanthus.
Agapanthus is propagated in two ways — by seed or by division of the clump. Once established, agapanthus can spread slowly by seed. Unlike berry-producing weedy plants, such as privet or cotoneaster, agapanthus is not spread by birds. Instead, seeds fall around the clump and have a tendency to drift downhill.
Agapanthus are easy to propagate by division to obtain plants identical to the parent plant, this is best done between spring and early summer. Avoid splitting plants too often as this will reduce flowering. Large clumps in the border should be lifted in spring every 4 - 6 years and replanted.