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Have you ever tried to winter-over a Mandevilla vine (Mandevilla spp.) indoors? I am trying it this year and would like to pass on information and tips I have (recently) researched on the Internet. The info below is a compendium of that information. Since they can be quite expensive, it may be worth your while to try it.
Mandevilla vines are sold by nurseries and “big box” stores throughout the summer. They are showy plants with trumpet-like flowers in many attractive colors. They are a tropical plant, only hardy to Zone 9 and above. If they are grown in hanging containers or in medium sized pots on the patio, they can be cut or pinched back to maintain the desired size. However, if it is happy in your location, i.e. sunny and warm, it will vine, and will need a large pot and some sort of trellis. It will thrive outside with regular, even watering, being careful to not let the soil get soggy. It needs well drained soil and light fertilizing at regular intervals when actively growing. They are moody if temps drop much below 60 degrees, and will NOT tolerate temps much below 45-50 deg.
If you pot it in a container on the patio, the container should be of adequate size to support good root growth and not be heavy. Resin pots can be quite large and still be lightweight – an advantage if you move it or take it in for the winter. The soil should be a good quality, light, porous potting medium. Make sure the pot has adequate drainage, cut more holes in the bottom if needed.
Some people treat Mandevillas as an annual, but they can survive inside in a sunny spot. Trim them back to about a foot tall, and leave them in their original container if possible. Take them in well before the danger of frost in the fall. Water them evenly, but keep them on the semi-dry side all winter. If new vine growth emerges after it is taken indoors, it will probably not bear any flowers. Since the plant likes bright sun, it will tolerate winter indoors but will not be truly happy unless your “indoors” is a greenhouse! Be sure to get rid of any insect pests before bringing them inside. An indoor temp of 65-75 deg should be quite satisfactory.
The crown and roots of the plant should survive the winter indoors with the above care, but don’t panic if most (or even all) of the leaves become mottled and/or fall off. It will NOT be a showy, flowering indoor plant for you even if you put it in a sunny window. You are just aiming for survival until spring, when it can be set outside again after all danger of frost is past. Wintering-over can be worth it, especially if it is a large plant, as they can be quite expensive to replace.
Prune your plant(s) in the spring, before new growth appears, if possible. Cut them back to within and inch or two of last year’s woody growth. New growth should appear as soon as they are receiving adequate sunlight and warmth when set out. If you need to repot, do it at this time, using the next bigger pot size.
Mandevillas can have pests. Whitefly, mealybugs, spidermites, scale and aphids are possible “guests”. Keep your eye out for any of these, especially when bringing them in from outdoors, or when they are close to other plants you have brought in.
With some luck and the above winter care, they will bloom profusely outside next year for you, and for years to come. Bon jardinage !