Creeping Jenny (Lysimachia nummularia) is a popular, low-growing ground cover known for its dense mats of coin-shaped foliage, often vibrant chartreuse or golden in the cultivar ‘Aurea.’ Gardeners use this hardy perennial for its trailing habit in containers or its ability to quickly cover bare soil. It typically does not die in winter, instead relying on specific biological mechanisms to survive the cold season.
Winter Survival Mechanism
Creeping Jenny is an herbaceous perennial, meaning the above-ground foliage dies back while the root structure survives the winter cold underground. This species is hardy across USDA Hardiness Zones 3 through 9, allowing it to withstand very low temperatures. Its survival depends on cold-weather dormancy, a natural defense mechanism that begins as temperatures drop consistently in the fall.
The plant redirects energy away from vulnerable stems and leaves, storing resources within its root system. This energy concentrates in hardy, underground stems known as rhizomes, which survive soil freezing. These specialized structures contain living buds and stored carbohydrates necessary to fuel new growth. Root tissues are significantly more cold-tolerant than exposed foliage, protecting the plant from freezing damage.
By entering this dormant state, the plant minimizes its metabolic activity, requiring less water and energy during winter. The living rhizomes remain below the frost line, insulated by the surrounding soil, waiting for spring. Once the ground warms, the stored energy is mobilized, and new shoots emerge, quickly re-establishing the ground cover.
Visual Changes During Dormancy
The appearance of Creeping Jenny changes dramatically as it prepares for winter, often leading owners to believe the plant has perished. In colder regions, the entire mat of foliage typically turns brown, withers, and dies back to the ground. This deciduous behavior is completely normal and is the visible manifestation of the plant entering its dormant, energy-conserving state.
In areas with milder winters, the plant may exhibit semi-evergreen behavior. The foliage may remain present but often loses its vibrant color, appearing flattened, dull, or developing a bronze tint. This is a response to reduced light intensity and colder temperatures, though the plant is still alive and maintaining minimal function. Even when the leaves appear damaged by frost, the root system remains viable below the soil surface.
The dieback is beneficial because it protects the plant from further cold damage and allows for a fresh, vigorous flush of growth in the spring. Once new growth begins, the old material can be easily cleared away to allow sunlight to reach the emerging stems.
Ensuring Successful Winter Survival
While Creeping Jenny is naturally cold-tolerant, preparation can significantly improve its survival, especially by managing the soil environment. For in-ground plants, the primary threat is the repeated cycle of freezing and thawing that can heave shallow root crowns out of the soil. To prevent this damaging action, a layer of insulating mulch should be applied only after the ground has frozen solid.
A two- to three-inch layer of organic material, such as straw or shredded leaves, applied over frozen soil acts as a blanket. This keeps the ground consistently cold and prevents temperature fluctuations. Before the ground freezes, ensure the soil is adequately moist, as dry soil loses heat and freezes more rapidly than saturated soil. Container-grown Creeping Jenny requires more intensive protection because the roots are exposed to cold air on all sides.
The soil mass in a container freezes much faster and deeper than ground soil, posing a serious risk of root death. To protect the roots, pots should be moved to a sheltered location, such as an unheated garage, shed, or cold frame. If moving them indoors is not an option, containers can be grouped closely against a warm structure, like a house wall, and insulated. Insulation involves wrapping the pots in materials like burlap or bubble wrap, or burying the entire container to use the earth’s natural thermal protection.