The delicate, colorful petals of Peruvian lily (Alstroemeria spp.) leads to other common names of parrot lily of lily-of-the-Incas. Many hybrid varieties grow in gardens, developed from crossing any of the 50 species. They go dormant in winter, but survive outdoors only in USDA hardiness zones 8 and warmer. Elsewhere, plant them in spring and lift them in autumn after the first frost for storage of tubers indoors.
The common name Peruvian lily attaches itself to any of the approximately 50 species of Alstroemeria native to the highland grasslands or montane screes of South America. Many species grow in the Andes Mountains of Chile, Argentina, Peru and western Brazil.
Plants grow from an underground rhizome-like tuber, a fleshy horizontal stem, that multiplies into a large clump. They yield upright twisting stems with green to gray-green leaves shaped like lances or straps from spring to autumn. In summer, flower stems rise just above the foliage and bear loose clusters of flowers called compound umbels. Each blossom comprises six petals and create a funnel-like form. Petals develop either a solid, uniform color with occasional speckles, or hybrid selections bear multi-colored petals of contrasting colors and large, prominent speckles and spots. Flowers range in all colors and combinations except black and true blue. As days shorten and temperatures approach freezing, the foliage dies and the underground tubers lay dormant until the soil warms next spring.
Where hardy outdoors in the garden, plant the tubers in autumn in any moist but well-draining soil that ideally contains sand or grit with organic matter. Keep soil dried in the winter when plants become dormant. Place them in partial shade to full sun locations, where at least four hours of direct sun reach the foliage daily. In hot summer climates, more shade in the heat of the afternoon proves best. A dry mulch over the dormant tubers helps them survive cool winters and allow the tubers to multiple and form large clumped masses for prettiest flower displays each summer. Some alpine-native species do not tolerate hot summers and grow best in cool, chilled greenhouses or only in mild montane regions.
In cold winter areas where not hardy, plant tubers in spring and allow to grow. Lift tubers after the first frost kills back foliage and brush away soil. Place them in dry sawdust or shredded newspaper in a tray and place them in a cool, dry place with temperatures between 40 and 50 degrees Fahrenheit.
Many people first encounter Peruvian lilies as cut flowers in a gift bouquet. In outdoor gardens, these cold-tender perennials make lovely additions to a mixed flower border, cut flower garden or cottage garden. Dwarf alpine species grow nicely in troughs and containers. Tubers of hybrids may also grow in seasonal containers for use as temporary house plants or rotating potted displays on patios.
Wherever grown, gray mold develops on flowers and a myriad of viral diseases plague these plants, especially when improperly watered or temperatures get too warm in summer. Slugs feast on the foliage and spidermites attack foliage in very arid conditions with little air circulation.
People with sensitive skin should avoid fondling the foliage, which may irritate and create a rash.