Alstroemeria, also known as the Peruvian lily or Lily-of-the-Incas, produces colourful flowers resembling amaryllis in shape. Colours include oranges, pinks, purples, reds, yellows and white, with many streaked or spotted varieties. As a cut flower, the alstroemeria is extremely long lasting. In the garden, it will self-seed after the first year, making it an effortless perennial addition to any spring and summer flowerbed.
In general, alstroemeria are cold hardy to USDA hardiness zone 5, where annual low temperatures average minus 20 to minus 10 degrees Fahrenheit. The plants can withstand soil temperatures as low as -5 degrees Celsius, though some hybrids may tolerate soil temperatures as low as 0-17.778 degrees Celsius. In zones 5 through 7, mulch around the plant's base to help conserve warmth in the ground. If you plant your alstroemeria in containers and move them indoors during the coldest months, they can even survive zone 4. Alstroemeria generally require full sun; look for a location where they will receive direct sun throughout the morning and into the afternoon. A notable exception is alstroemeria psittacina, which prefers partial to full shade.
Alstroemeria need moderate watering throughout growth and blooming. Be careful to avoid overwatering, however. The flowers require that soil be moist but well-drained. If you plant them in containers, check that the pot has sufficient holes in the bottom for drainage. If planting outdoors, avoiding planting in depressions, at the bottom of slopes or in marshy land. Improve the drainage of clayey soil by adding loamy potting soil or compost. During winter dormancy, the tubers do not require watering.
Alstroemeria grow from tubers, much like flowering bulbs, and they undergo a dormant period through the winter. Plant the tubers at a depth of 8 inches, spaced around 12 inches apart, in the late summer or early fall. Expect blooms by late spring or summer. When full grown, the flowers should measure between 12 and 48 inches tall. While many alstroemeria are deciduous and fully dormant during the cold months, evergreen varieties are increasingly available for home gardeners. These varieties continue blooming through mild winters. Pull up flowering shoots from the base to trigger repeat flowering.
Protecting from Pests and Disease
Protect your alstroemeria from typical problems, such as grey mould, viruses, spider mites or slugs. Keeping the plant from developing "wet feet," with well-drained soil, will help to protect it from grey mould. Introduce "friendly" insects, such as ladybirds, to protect against spider mites. Other natural enemies to the spider mite include minute pirate bugs, big-eyed bugs (Geocoris species) and predatory thrips.