Hope this answers your question Dyanne and Margaret....thanks for asking. Makes for easier blog pages when the gardeners ask....
Winter Care for Dipladenia Written by Jenny Harrington;
Tropical dipladenia vines (Mandevilla spp.) can grow up to 10 feet tall in warm, U.S. Department of Agriculture hardiness zones 9 through 11. Dipladenia is the former name of the plant, with most cultivars now properly labeled and sold as mandevilla vines. They can survive in USDA zone 8, although they may die back each year and grow as shorter plants. The tall vines produce 4-inch-diameter pink, red, white or yellow flowers and lush foliage that remains evergreen in warm climates. Proper winter care ensures that the dipladenia will survive to bloom again each summer.
Dipladenia vines usually survive winter with little preparation in USDA zones 9 through 11, but they do benefit from some insulation in zone 8. If light frost sometimes occurs in your area, water the plant to help conserve heat to the roots, mulch over the roots with a two- to three-inch layer of straw, bark or other insulating mulch. Frost or extended cold may still kill back the aboveground portion of the vine, but the roots will survive and send up new shoots in spring.
The vines remain evergreen in frost-free areas, but they do go semidormant so they don't need fertilizer in winter until they begin to send out new growth in spring. Dipladenias do benefit from light winter watering. Provide enough water so the soil doesn't dry out completely, but avoid overwatering and constantly wet soil. The soil dries out more slowly during the cool, damp winter days, so check the soil moisture near the base of the dipladenia before you water. If the top few inches feels moist, the plant doesn't need watering.
Light pruning in late winter or spring cleans up the dipladenia before it begins filling out again in spring. In mild areas where little dieback occurs, prune out any dead or bare stems. You can cut out any old, crowded stems and shorten the entire plant to the desired height. If winter dieback does occur, cut back the entire vine to the ground. It will send up new shoots if the roots survived. It will still flower that summer, even if you have to remove the entire vine to ground level. Always used sterilized pruning tools so you don't transfer disease to the plant.
Potted dipladenia may not survive in USDA zone 8, or in other areas where temperatures drop below 45 degrees Fahrenheit in the winter. Bring these plants indoors in fall for safe overwintering. Rinse the entire plant with a sharp spray of water to dislodge any pests before bringing the vine inside to dislodge any insects hiding in the foliage. Keep the plant near a window that receives all-day sunlight where temperatures remain above 45 degrees F. The dipladenia only needs watering when the top two inches of soil begins to dry. The foliage may die, but the plant should produce new foliage in spring
taken from https://homeguides.sfgate.com/winter-care-dipladenia-
Gardening Know How - https://www.gardeningknowhow.com
Growing Mandevilla Vine Indoors: Caring For Mandevilla As A Houseplant
Mandevilla is a native tropical vine. It produces masses of bright, usually pink, trumpet-shaped flowers which may grow 4 inches across. The plants are not winter hardy in most zones of the United States and have a temperature minimum of 45-50 F. (7-10 C.). Unless you are in the tropical south, you will need to grow mandevilla as a houseplant. This plant has particular needs and growing mandevilla vine indoors can take some space.
Mandevilla Growing Conditions
The vine is hardy to USDA zone 9, which means you need to grow mandevilla as a houseplant during the fall and winter in cooler climes. In nature the vines twine around any available edifice or support and can grow up to 30 feet in length.
They prefer partial sun in rich moist soil with plenty of organic matter. As outdoor plants, they need water frequently and fertilizer every two weeks in spring and summer with a high phosphorus food.
The plant will go dormant in winter and may even lose some of its leaves but will regrow when spring warms up the air. The best temperatures for mandevilla are above 60 F. (15 C.) at night.
Mandevilla as a Houseplant
Moving the plant to the interior provides different growing conditions for it. Therefore, it is important to know how to care for mandevilla indoors. Mandevilla houseplants should not be moved inside until you are sure there are no bug hitchhikers.
Mandevilla houseplants are a bit fussy and require special growing conditions. In its habitat it can grow 7 to 10 feet per season, so this isn’t a little counter top or window box houseplant. Trim the plant as needed to keep it in the confines of the room in which it is growing.
A greenhouse environment is ideal or you can grow the plant near a sunny window with some protection from scorching midday sun. If you are growing mandevilla vine indoors, don’t be surprised if it doesn’t flower. You would need excess high artificial light to force buds and blooms. The plant will not bloom when overwintering mandevilla inside and goes dormant until brighter spring light arrives.
How to Care for Mandevilla Indoors
You can just grow it like a regular plant inside or you can cut it back to just 8 to 10 inches and pot it up. Move the pot to a cool, dim area where temperatures average 55 to 60 F. (13 to 15 C.).
Cut watering in half during the dormant period and remove spent leaves and dead plant material in spring. The indoor mandevilla plant needs to remain fairly dry to prevent rot.
Keep the indoor mandevilla plant moderately dry over the winter and with a little luck you will see sprouts in spring. Move the pot to a sunny location and pinch the shoots to force bushier growth. Start fertilizing every two weeks with a high phosphorus plant food.
taken from Article printed from Gardening Know How: https://www.gardeningknowhow.com
till next time this is Becky Litterer, Becky's Greenhouse, Dougherty Iowa firstname.lastname@example.org