Alstroemeria, commonly known as the Peruvian Lily or Lily of the Incas, is a highly favored flower in the cut flower industry due to its vibrant colors and exceptional vase life. This South American native is botanically classified as a tuberous-rooted herbaceous perennial, meaning it possesses underground storage organs that allow it to live for multiple years. The designation of “perennial” is not absolute, however, as its ability to return each spring depends entirely on the climate and the severity of winter temperatures. For most gardeners, Alstroemeria is best understood as a tender perennial whose long-term survival is determined by the local hardiness zone.
Climate Determines Perennial Status
The classification of Alstroemeria as a tender perennial highlights the plant’s sensitivity to cold. A perennial is defined as a plant that lives for more than two years, but a tender perennial lacks the necessary hardiness to withstand freezing temperatures without protection. For Alstroemeria to be a reliably returning perennial, it must be grown in regions corresponding to USDA Hardiness Zones 8 through 10, where the ground does not freeze deeply or for extended periods.
In these warmer zones, the plant’s fleshy, tuberous roots can remain in the ground year-round, entering a brief dormancy before resuming growth in the spring. Gardeners in borderline areas, such as Zone 7, may find success, particularly with newer, hardier cultivars that are sometimes bred to tolerate colder conditions. Outside of these established warmer zones, Alstroemeria must be treated as a seasonal annual or requires specific human intervention to shield its tubers from frost damage.
Basic Care for Healthy Blooms
During the active growing season, from spring to fall, Alstroemeria requires consistent conditions to produce its prolific, lily-like blooms. The plant thrives in a location that receives full sun to partial shade, though it benefits from afternoon shade in climates with intense, hot summers to prevent scorching of the foliage. The soil composition is highly important for the health of the tuberous roots, requiring a fertile, well-draining medium that is slightly acidic.
The dense root system is susceptible to rot, so while the plant needs consistent moisture, it cannot tolerate soggy or waterlogged conditions. Incorporating organic matter, such as compost, at planting time helps improve drainage while providing necessary nutrients for strong growth. An application of a balanced, slow-release fertilizer in early spring supports the season’s heavy flowering period. To encourage continuous blooming, spent flower stems should be removed by gently pulling the entire stalk from the base, which stimulates the plant to produce new shoots.
Overwintering Strategies
For gardeners in colder climates where Alstroemeria is not reliably perennial, specific strategies must be employed to protect the tubers over winter. In transitional zones like Zone 6 and 7, where cold snaps are common but not consistently severe, a heavy layer of insulating mulch can provide enough protection. After the foliage dies back following the first hard frost, a thick layer of organic mulch, such as straw or shredded bark, should be applied approximately six to eight inches deep over the planting area.
In regions with very cold winters, the tubers must be lifted and stored indoors to survive the deep freeze. This process involves carefully digging up the fleshy roots after the foliage has withered and allowing them to dry slightly to prevent fungal issues. The dried tubers should then be packed in a cool, dark, and dry medium like peat moss, sawdust, or wood shavings. Storing the tubers in a location that maintains a consistent temperature between 35° and 45°F, such as a cool garage or basement, will keep them dormant until they can be replanted in the spring after the danger of frost has passed.