The plant known as ‘Mona Lavender’ (Plectranthus ‘Mona Lavender’) is a popular ornamental hybrid featuring dark green, glossy leaves with deep purple undersides and tall spikes of lavender-purple flowers. Often sold as a colorful bedding accent for shade gardens or containers, its perennial status is nuanced. ‘Mona Lavender’ is botanically classified as a tender perennial, meaning its ability to survive year after year depends on the climate in which it is grown. In many regions, it cannot endure winter cold and must be treated as an annual plant.
The Climate Dependency of Perennial Status
‘Mona Lavender’ is a tropical hybrid originating from South African Plectranthus species, which dictates its low tolerance for cold temperatures. Its permanent survival is limited to the warmest regions of the United States, specifically USDA Hardiness Zones 9 through 11.
In these zones, temperatures rarely dip below freezing, allowing the plant to act as a broadleaf evergreen shrub. It can bloom from late summer and continue through the winter. The plant thrives in year-round temperatures ranging from 60 to 80 degrees Fahrenheit, though it may briefly withstand temperatures as low as 25 to 30 degrees Fahrenheit. Even in Zone 9, a hard frost can cause significant damage.
Outside of these mild areas, ‘Mona Lavender’ is not winter-hardy and will perish if left outdoors. Gardeners in cooler zones use it as a seasonal annual, enjoying its foliage and flowers until the first frost kills the plant. The term “tender perennial” acknowledges its biological potential for longevity while recognizing its practical limitation in temperate climates.
Strategies for Overwintering the Plant
Gardeners in colder zones use two methods to preserve ‘Mona Lavender’ through the winter. The first involves bringing the entire potted plant indoors before the first expected frost. It should be placed in a location that receives bright, indirect light, such as a sunny window.
During this indoor period, the plant enters a semi-dormant state and requires reduced care. Watering must be reduced, providing moisture only when the top inch of soil feels dry. Fertilization should be halted over winter, as the plant is not actively growing and will not bloom until days lengthen.
A second, space-saving strategy is to take stem cuttings in the fall for propagation. Four- to six-inch cuttings from the tips of healthy stems root easily in moist potting mix or a glass of water. Rooting these small starts indoors maintains compact plants over winter, ensuring new plants are ready for the garden once the danger of frost has passed.
Optimal Growing Conditions
‘Mona Lavender’ performs best when provided with specific conditions during the active growing season. The plant prefers a location with partial shade or dappled light, thriving especially well with morning sun and protection from harsh afternoon heat. Although it tolerates full shade, foliage and flower color may not be as intense without some bright light.
It requires consistently moist, well-draining soil that is rich in organic matter to prevent soggy conditions. Due to its tropical nature, ‘Mona Lavender’ is a thirsty plant and should be watered every few days, or whenever the top layer of soil has dried out. To encourage a dense, bushy shape and abundant flowering, the stems should be routinely pinched or pruned.