Mandevilla plants are popular for their vibrant, trumpet-shaped flowers and vining growth, adding a tropical flair to gardens and patios. Originating from warm regions, Mandevillas are sensitive to colder temperatures, which dictates specific care requirements for their successful growth.
Understanding Mandevilla’s Temperature Needs
Mandevilla species are native to the tropical and subtropical regions of Central and South America. This natural habitat provides them with consistently warm temperatures and high humidity. Ideal daytime temperatures for Mandevillas range between 60°F and 80°F (15°C and 27°C). Nighttime temperatures should not drop significantly below 60°F (15°C). Maintaining these temperature ranges promotes vigorous growth and abundant flowering.
Critical Low Temperature Thresholds
Mandevilla plants can tolerate brief, non-freezing dips in temperature, but prolonged exposure to cold causes significant damage. While they might survive short periods down to around 40-45°F (4-7°C), sustained temperatures in this range will induce considerable stress. Temperatures at or below freezing, specifically 32°F (0°C), are typically fatal for Mandevilla. Frost formation within plant cells ruptures membranes, leading to irreversible tissue destruction.
Even temperatures slightly above freezing, if sustained for many hours, can lead to chilling injury, which is different from direct frost damage. Chilling injury manifests as a decline in plant vigor and can make the plant more susceptible to diseases. A short, unexpected cold snap might be survivable with protection, but a prolonged period of cold weather below their ideal range will severely compromise the plant’s health.
Identifying Cold Damage
When a Mandevilla plant has been exposed to low temperatures, it will exhibit distinct visual symptoms. Leaves may appear blackened or water-soaked, indicating cellular structures have been compromised by cold. Wilting is another common sign, and stems might also show discoloration, turning brown or black. Developing flower buds may fail to open, turn brown, or drop off. These symptoms are direct results of cell damage caused by freezing or extended periods of chilling.
Protecting Mandevilla from Frost and Cold Snaps
Protecting Mandevilla plants from sudden drops in temperature is important, especially during unexpected frost warnings. For potted Mandevillas, the most effective immediate measure is to bring them indoors to a warmer environment. If the plant is too large to move, or if it is planted directly in the ground, covering it with a frost cloth, burlap, or a thick blanket can provide temporary insulation. These covers should extend to the ground to trap residual heat from the soil. Ensuring the plant is well-watered before a freeze can also help, as moist soil retains heat more effectively than dry soil. Temporary shelters, such as plastic sheeting draped over stakes, can also offer some protection against direct cold winds.
Overwintering Mandevilla
In regions where winter temperatures consistently fall below a Mandevilla’s tolerance, overwintering the plant indoors is a common practice. This process typically involves preparing the plant to enter a dormant or semi-dormant state for the colder months. Before bringing the plant indoors, it is beneficial to prune back the vines by about one-third to one-half, which helps manage its size and encourages bushier growth in spring. A thorough inspection for pests is also crucial to prevent infestations from spreading indoors.
Once inside, Mandevillas can be overwintered in different ways depending on available light and desired growth. For dormancy, place the plant in a cool, dark location, such as a garage or basement, where temperatures remain consistently above freezing, ideally between 45-55°F (7-13°C). Reduce watering significantly, only providing enough to prevent the potting mix from completely drying out. If a brighter, warmer location is available, such as a sunny window, the plant may continue to grow slowly, requiring more consistent watering and occasional feeding. Regardless of the method, proper air circulation helps prevent fungal issues during the overwintering period.