Agapanthus is a popular garden and landscape plant that is easy to grow and relatively disease free. As long as they are planted in the right conditions and protected from the cold, the plants require very little maintenance, yet reward gardeners with their graceful fleshy leaves and beautiful blooms.
Agapanthus, or "Lily of the Nile," is a perennial plant species prized for its use in the garden. The plants grow and spread by a partially buried rhizome, producing fleshy bundles of tender leaves and 36- to 60-inch tall inflorescence. The flowers are arranged in a globular structure, similar to allium, and are available in white, purple, periwinkle and pink.
Agapanthus are native to Africa and the Mediterranean, so they generally require mild winters and warm summers. They are hardy in USDA zones 7 -11, where they can be left in the ground all year as long as winter temperatures do not drop below -6.67 degrees Celsius. In colder regions, they are typically grown as a potted plant, which can be moved indoors during the winter. If planted in the garden, they can remain in the ground for winter under a protective layer of heavy mulch. Freezing temperatures cause the leaves of the plant to turn brown and mushy, eventually killing the plant once the crown & rhizome freeze.
Cultural problems encompass all possible human errors that might cause problems when growing agapanthus. These include: improper soil mixture, potting, fertilising and placement in the garden. Agapanthus should be grown in a light, fast-draining soil, enriched with leaf mould and composted manure. For container plants, use a well drained potting mix with a granular fertiliser added. If the soil drains too slowly and retains excess water, the plant will suffer from root and rhizome rot. Agapanthus should be planted with their rhizome 2 inches deep (4 to 6 inches deep in cold climates). If planted too shallow, the plant will dry out too quickly and not transplant well. If planted too deep, the plant will waste energy pushing its growing tips through the soil and will remain too moist, increasing the chances of rot. Agapanthus should be planted in full sun unless you live in a hot, dry climate, where they should be placed in partial shade. If placed too deep in the shade, they will fail to bloom as they do not have enough energy to produce flowers.
The most common pests that affect agapanthus are snails, red spider mites and mealy bugs. Snails love to munch on the fleshy stems of agapanthus, damaging the leaves and flower stalks. Snails can be dealt with using copper garden strips and/or snail bait. Spider mites and mealy bug damage is not as obvious as snail damage, but they are easy pests to deal with. Use an organic horticultural oil mixed in a pressurised sprayer to spray each plant once a month. Horticultural oil dissolves and clogs the waxy coating on insects, killing them without damaging the plant or environment.
Agapanthus are generally disease free, though they occasionally suffer from root/rhizome rot if planted in slow-draining soil. Garden soils high in clay and low in organic matter tend to hold moisture and become water logged, eventually asphyxiating the roots of the plant. Water logged soils also serve as an ideal breeding ground for soil-borne fungal diseases. To combat this, dig and turn over the soil in the desired planting area and incorporate composted manure and perlite to aerate the soil and improve drainage.