Alstroemeria, commonly known as the Peruvian Lily, is a popular perennial valued for its long-lasting, brightly colored blooms that make it a favorite in cut flower arrangements. Successfully carrying these plants through the colder months requires specific preparation. The approach to winter care depends entirely on the local climate and how deep the ground freezes.
Understanding Cold Tolerance
The winter survival of Alstroemeria hinges on protecting its fleshy, underground storage organs, known as rhizomes. These shallow structures store energy and moisture during dormancy. If the soil temperature drops low enough to freeze the rhizomes, the plant is at high risk of damage or death.
Alstroemeria is generally suitable for in-ground survival in regions where temperatures typically remain above 20°F. If the local climate regularly sees temperatures plunge below this threshold for extended periods, the rhizomes are unlikely to survive without intervention. This temperature dictates whether a gardener must lift the plant or simply heavily insulate it in place.
Pre-Winter Preparation
Preparing Alstroemeria for winter begins in late fall, well before the first hard frost. Observe the foliage for natural dieback as temperatures consistently cool. Once the leaves start to yellow and fade, signaling the end of the active growing season, it is time to intervene.
The spent stalks and yellowing foliage should be cut or carefully pulled back to ground level. Removing this material helps prevent fungal diseases that thrive in cool, damp, decaying plant matter during dormancy. This step prepares the plant for either in-ground insulation or lifting.
As the plant naturally enters dormancy, significantly reduce watering frequency. Excess moisture in the soil during this cool period can lead to rhizome rot, especially if the ground is prone to staying cold and waterlogged. Encouraging this dry, dormant state is necessary for healthy winter survival, irrespective of the final overwintering location.
Overwintering Strategies
In-Ground Insulation (Milder Climates)
For gardeners in milder climates where the ground rarely freezes solid, leaving the rhizomes in place is the preferred and least disruptive method. The strategy focuses on insulating the soil to stabilize temperatures and protect the shallow roots from intermittent freezes and thaws. This temperature fluctuation is often more damaging than a steady, deep freeze.
A generous layer of insulating material should be applied directly over the planting area after the foliage has been removed. Materials such as shredded bark, straw, or pine needles work well because they trap air and resist matting, which could otherwise suffocate the rhizomes. The mulch layer needs to be substantial, typically applied to a depth of four to six inches.
This deep layer acts as a buffer against cold air penetration and helps maintain a consistent soil temperature throughout the winter months. The material must be loose and dry when applied to prevent moisture buildup around the dormant rhizomes, which increases the risk of rot.
Lifting and Storing (Colder Climates)
In regions where prolonged temperatures below 20°F are common, the rhizomes must be lifted from the soil for protected storage. Use a garden fork to carefully loosen the soil around the plant, avoiding slicing the brittle rhizome mass, and extract the entire clump.
Once lifted, gently brush the soil off the rhizomes without washing them, which introduces unnecessary moisture. If the rhizomes appear bruised or damaged, dusting the clump with a fungicidal powder offers protection against fungal decay.
The prepared clumps are then placed into a breathable container, such as a cardboard box or a mesh bag, for the winter. The rhizomes should be completely surrounded by a dry, lightweight medium like peat moss, vermiculite, or wood shavings. This material helps absorb any residual moisture and provides insulation.
The storage environment must be cool, dark, and dry to maintain dormancy and prevent premature sprouting or dehydration. An ideal temperature range is between 35°F and 45°F, often achieved in a cool, unheated basement, root cellar, or insulated garage. Monitor the stored rhizomes occasionally for signs of rot or shriveling to ensure a healthy transition into the spring.
Revival in Spring
The transition back to active growth begins when the danger of the last hard frost has passed. For plants overwintered in the ground, gradually pull back the thick layer of insulating mulch from the crown. Removing the mulch too early risks exposure to late frosts, but leaving it on too long can inhibit new shoot emergence and trap excessive moisture.
Gardeners who lifted their rhizomes should replant them into prepared garden beds or containers around the same time. Place the rhizomes just a few inches below the soil surface, similar to their original planting depth. This timing allows the plant to establish itself before the heat of summer arrives.
Initial care involves a gradual reintroduction of water to encourage the first signs of green shoots. Once new growth is visible, incorporate a light application of a balanced, slow-release fertilizer into the soil. Providing this initial nutrient boost supports the vigorous development of the upcoming season’s foliage and flowers.