When Agapanthus get overcrowded, you need to divide them. At the end of their bloom cycle you need to deadhead them. Other than that they don’t require much care except regular watering.
Deadheading Agapanthus blooms is a matter of clipping the spent blooms and disposing of them. Reach down along the stem and clip the bloom. Dispose of the seed heads in your garden debris pile.
Dividing Agapanthus reduces overcrowding, gives the roots more room to grow, and encourages more blooms. The bloom cycle of Agapanthus is about two weeks.
Loosen the roots on the outside, then place the show will between two clumps and divide them by cutting through the roots. This will make smaller clumps easier to remove.
After digging all the clumps of Agapanthus. It is time to divide individual plants and dispose of the extra. The extra plants can be moved to another area of your garden, given away to your neighbors or disposed of in your compost pile.
Separate the entwined roots of the individual plants by hand or by cutting with a sharp knife, planting pic, or shovel. Keep the nicer plants with good root system for replanting in your rows.
Dig your holes for replanting about the diameter of a 1 gallon pot by half the depth. You’re planting holes approximately 1 foot apart on a triangulated layout. If there is a curve to the base of the plant point the curve away from the other plants to allow the roots to grow unhindered.
Make sure the plants are standing upright, with the roots spread out, pressed firmly into the soil and not planted too deep. It is better to plant most plants too high than too low. When you place a plant too deep in the soil it has a tendency to get a crown rot.