Don't get me wrong; agapanthus are real survivors and they're great choices for those impossible spots in your garden. I use them in the sandiest, driest and sunniest patch of hades that my garden has to offer, and they do just fine. I just want to show you how beautifully these amaryllis relatives perform with the right treatment, and show you just what the right treatment is in the first place!
While many references describe lily of the Nile's cultural requirements as something along the lines of "well drained soil with regular moisture in full sun to part shade" let me take it a step further and elaborate a bit.
Well drained soil is the tofu of cultural requirements. I once found an entire book with every single plant requiring this elusive "Well Drained Soil" and personally think that sometimes it's just an assumption on the author's part. My most impressive clump of agapanthus lives on a little mound at the edge of a seasonally flooded swamp, and at times the little mound becomes a little island, particularly during tropical storms.
What has killed or damaged agapanthus in my experience is the kind of water that inundates the plant above the crown or overwhelms young and unestablished plantings. The big killer is winter moisture though. If your garden is hit with an unexpected deluge during what would normally be a dry season, you can always cover the plants or dig them up outright to rescue them from the cold and damp soil that would be their demise.
|Agapanthus looking unhappy in a parking lot median.|
Regular moisture is also relative. Lily of the Nile can lose its top growth during a drought and flourish once regular rainfall resumes! As far as sunlight goes, the more sun the plant gets, the more water you have to provide. My healthiest looking clump is in a shady spot with some dappled sunlight, so shade isn't a problem either. In sunlight the mounds of leaves become tighter and more upright, and might become a little yellowed. In shade however the clumps are loose and elegant, with a fountainlike form and a glossy deep green color. The inflorescences are also taller and fuller in my experience. You can probably guess how I like my agapanthus.
Division can be carried out by division or seeds. Since these plants don't like to have their roots disturbed and don't mind a little crowding, it's best to only divide every 3-5 years. It takes about a year for newly divided plants to re-establish themselves... so my vote goes to the easier (though longer) method of collecting and sowing seeds.
Usage in the Landscape
Lilies of the Nile are usually enjoyed as perennials or groundcovers. A dense bed of blue agapanthus blooms dangling delicately in a breeze is a true sight to behold, especially when they're set off against a dark and shady backdrop. Combine the apple green strappy leaves with contrasting foliage or along with other perennials with a fountainlike form such as spider lilies, liriope, bromeliads or grasses. Perennials with harmoniously colored flowers include salvias, ("Black and Blue" is a good one) society garlic, plumbago, tibouchina, passionflowers and ruellia. Ruellia would look really nice behind a planting of agapanthus too, come to think of it!
Cultivars like "Queen Anne" can be large and formidable, while dwarf forms like "Peter Pan" are small enough to be used as an edger or like you would use mondo grass. Most of the plants seen at nurseries are either Agapanthus orientalis or hybrids of it, but adventurous gardeners will find more unusual species if they look hard enough. The one I'd love to get for myself is A. inapertus, a deciduous species with deep blue to purple drooping blossoms.