Outdoor growing tips
(Zones 6 and up)
Choose hardier deciduous cultivars, such as A. Headbourne Hybrids and 'Lilliput', planting the rhizomes about five centimetres deep to prevent frost damage. Select a sunny site with good drainage. Although this genus is not particularly fussy about soil type, I've found that very fertile soils tend to produce lush vegetation with few flowers. A southern- or western-facing foundation bed near the house is an ideal location, providing much appreciated reflected heat in summer and residual heat in winter to help protect the rhizome from ground frost. The building foundation and adjacent sidewalk or patio also help constrain the root system, which I believe aids in flower development. In coastal B.C., winter rains can cause the crown to rot, so look for a location beneath a roof overhang.
Don't feed Agapanthus too much nitrogen, as this may cause lush foliage, which is susceptible to fungal disease. As new leaves emerge, watch for slugs and snails. Once foliage has died down, overwinter deciduous garden Agapanthus by placing a 10-centimetre-thick layer of mulch over its crown. Use coarse bark nuggets (especially in wet winter areas), straw or leaf mulch. If attempting to grow evergreen types outdoors (only recommended in Zone 8), mulch around the crown and protect the exposed evergreen foliage during the coldest months with a teepee of cut conifer boughs.