I've a Mandevilla Plant That Suffered Frost Damage and It Appears Dead: Will It Come Back?
Mandevillas (Mandevilla spp.) Are prized for a vigorous growth habit and showy, trumpet-shaped flowers available in shades of pink, yellow, red and white that appear to the plants continuously throughout most of the growing season. These tropical plants develop as perennial vines in U.S. Department of Agriculture plant hardiness zones 9 to 11, though they are potentially elongated as annuals or overwintered inside across a much wider range. Frosts and even extended periods with temperatures under 55 degrees Fahrenheit may injure a mandevilla, sometimes extensively enough that it isn’t apparent if the plant has survived.
Inspection and Immediate Action
Flowers and leaves may drop from a frost-damaged mandevilla rather quickly, but it may not be as easy to tell if stems survived. To check if a part of stem is still living, use your fingernail or a sharp, clean knife to gently scrape off a small part of outer bark and observe the colour of their underlying tissue. If it is green, that portion of this plant is still living. If the tissue is brown or dark, it is dead. If the mandevilla was not entirely killed by the frost, then it will still benefit from regular irrigation, though it takes less water than it did before it was injured and when it was actively growing. Whenever rain is inadequate, irrigate the mandevilla deeply so that the dirt around the plant’s roots never dries out completely, or when dirt a few inches under the soil surface close to the mandevilla base feels dry to the touch.
Put off Pruning
Though it may be tempting to prune off dead parts of the mandevilla the moment you determine the extent of the damage, wait to trim off dead mandevilla stems until all danger of additional cold injury has passed. The dead portions staying attached to this plant offer slight protection against additional cold injury. Pruning prematurely may also stimulate a feeling of tender new development susceptible to injury during any additional cold weather.
Perform Corrective Pruning
Once you determine the approximate area of the damage, or new development has started to emerge and all danger of cold damage has passed, then you can prune off dead segments of the mandevilla. Use sharp, clean pruning shears or loppers to make angled cuts to living, green tissue just above a bud. If it appears as if the mandevilla stems were murdered back entirely, with no green tissue visible aboveground, cut the stems to about 6 inches above ground level. If the root system survived the chilly weather, new development may still emerge within a month or two.
Prevent Future Problems
If the mandevilla survives, or if it does not and you choose to replace it with a brand new mandevilla, particular care clinics can help lessen the likelihood that the mandevilla will suffer damage as widely in following years. Keeping up a layer of organic substance mulch 3 to 4 inches thick over the ground around the mandevilla regulates soil temperature and helps to protect the mandevilla roots and overhead against injury. Make sure that the mandevilla receives adequate irrigation from the weeks leading up to potential cold events, as a drought-stressed plant is far more vulnerable to cold injury. In addition, do not apply fertilizer to the mandevilla in late autumn or early winter, since this will encourage a flush of tender new growth.