Cyrtanthus is grown mainly for its striking, sometimes sweetly scented flowers, and certain species have interesting, spirally twisted leaves, or exposed bulbs, covered with papery tunics. The genus comprises two main growth forms, evergreen and deciduous members, and within the latter group there are both summer- and winter-growing species. The evergreen members are usually of easier culture than the deciduous ones, and many of the latter are challenging to grow, and suited only to the specialist grower. 

Fig. 7. Two evergreen species, Cyrtanthus sanguineus and C. montanus. Photos Graham Duncan

In general, cyrtanthus like a sheltered but well-ventilated environment, receiving morning sun, or light shade throughout the day, however, certain species, such as the evergreen C. obliquus, thrives in full sun. Many species, especially the smaller ones, are very well suited to containers, placed on a covered patio, or a windowsill. Evergreen species such as C. brachyscyphus, C. elatus, C. mackenii and C. sanguineus, can also be grown in hanging baskets, and these species also perform well as bedding plants. An acid or neutral growing medium that drains well, is preferred, such as equal parts of loam, finely sifted, acid compost and coarse grit/river sand. Depending on mature size, plant the bulbs in 20 cm, 25 cm or 30 cm diam. pots, with the bulb necks exposed. For evergreens and deciduous summer-growers, plant in spring, and for deciduous winter-growers, plant in autumn. In cold climates, terracotta pots are most suitable, but in warm parts, plastic pots are preferable. Provide an initial heavy watering, and repeat once per week or every 10 days for the duration of summer or winter, as the case may be, allowing the medium to dry out substantially between applications of water. During the dormant period, keep the soil dry for deciduous species, and reduce watering of evergreens.

Many cyrtanthus, especially the evergreens, can be propagated by offsets, but some of the deciduous species have solitary bulbs, and are most feasibly propagated by seed. Separate offsets from the mother bulbs in spring, and replant immediately. Certain species, such as C. labiatus and C. montanus, form numerous bulblets beneath the bulb tunics. Remove bulblets when large enough to handle, and establish them in pots for a year, before planting out. Harvest seeds as soon as the dry capsules begin to split, otherwise they will soon be lost during wind gusts. As seed viability is limited, sow seed in containers as soon as it is ripe, in a sandy medium. Alternatively, store seed for up to six months in sealed containers in a fridge, before sowing. Prior to sowing, moisten the soil surface with a watering can, to prevent seeds ‘floating’ to the surface, sow thinly, and cover with 3-5 mm of sowing medium. Germination of fresh seeds takes place within about three weeks. Allow seedlings to establish themselves for two years, before planting out. Cyrtanthus can also be propagated vegetatively by means of bulb explants, under laboratory conditions, however this method is beyond the scope of the home gardener.            

In summer, the leaves, flower stems and flower stalks of cyrtanthus are highly susceptible to attack by lily borer caterpillars, which can also destroy the bulbs, in severe infestations. Cyrtanthus bulbs are subject to attack by mealy bugs at any time of year, and snails occasionally freed on the leaves and transfer viral disease. The roots of most species are highly susceptible to fungal disease, usually caused by insufficiently well drained growing media.