Agapanthus (African lily) can add a beautiful and showy flash of purple, blue or white to the garden during the late summer months. While these vibrant perennials thrive throughout the southern hemisphere (whilst on a trip to New Zealand last year, no-one could quite believe that we actually cultivate and sell them as a valued plant here, they are almost a weed there), they aren’t quite as easy to grow in Scotland, although they tend to do best in well-drained and dry coastal areas, such as the East Neuk.
Agapanthus make excellent focal points for a sunny spot and often perform best when planted in containers as they like to have their roots constrained. Growing them in this way also gives you the option of bringing them into a sheltered spot away from the worst of the wet and hard frosts over the cold winter months.
For single plants choose pots approx. 20-23cm (8-9in) in diameter, fill with compost (the RHS recommend John Innes No 2 or No 3 potting compost but multi purpose or even better, peat reduced is perfectly fine) and don't plant too deeply. Most Agapanthus are fully hardy and can be left outside throughout winter, especially when planted in the ground. Those in pots will also cope quite adequately with being left outside but they may start into growth rather later so another option is to place them in a light, dry, frost-free place in late autumn - e.g. a cold frame or greenhouse. However, when we have tried this with the Agapanthus in the nursery we have brought them out in early May to get them hardened off and to avoid too much soft growth only to have all the new bright green shoots killed off by late frosts which has just set them even further back therefore achieving absolutely nothing!!!! Definitely avoid overwintering the plants in warm conditions or planting them in containers which are too large - this can reduce flowering.
Agapanthus can be divided in September if the weather is mild but Spring is really the best time to propagate by this method. Wait until your plants have finished flowering and divide the plants ensuring there are a couple of growing shoots in each division. Large clumps should be split every three to four years.
Agapanthus can also be propagated by seed. Collect pods as they turn brown in autumn and allow them to split apart indoors. Store in a cool, dry place and sow in spring in a temperature of 15°C (55°-59°F). Protect seedlings in their first winter in a cold frame or unheated greenhouse. If you want to do it this way you will have to be patient - flowering from seed takes three to four years!