Extension Educator, Horticulture
Gardeners are wild about tropical bloomers. As wild as a Hawaiian shirt, tropical flowers bring an exciting look to gardens. Being tropical means these plants won't make it through our winters. So do we let them die a cold death? Of course not! We are gardeners who hold on to each plant until the last cell loses chlorophyll. In addition many of the tropicals such as mandevilla and brugmansia actually flower better as the plant matures. Here are a few tips to keeping tropicals through the winter for continued beauty next season.
Mandevillas are dramatic vining plants with large glossy leaves and magnificent trumpet shaped flowers. Flowers are pink, white or a new one called Best Red. Mandevillas lend a tropical flair to landscapes as they twine around trellises, fences, lampposts, or mailboxes and often grown in containers. Like many tropical vines mandevillas are fast growers putting on 7 to 10 feet per season. They can eventually reach 30 feet in the south or in a large greenhouse. They are hardy to Zone 9, so they don't survive temperatures much below 55 degrees F.
The other method is the "just don't die" method. Dig the mandevilla from the garden or bring in the container before temperatures get below 60 degrees F. Trim the plant back to about 8-10 inches. Wash plant thoroughly. Drench container soils with water to encourage any critters like ants and sowbugs to vacate. Store the plant in a cool dark basement, garage or crawlspace. Anywhere where the temperatures stay about 55-60 degrees is adequate. Do not fertilize during the winter. Keep the soil on the dry side, but do not let it dry out completely.
In the early spring the plant will form shoots. Move it to a sunny spot indoors and pinch shoots periodically to form a bushier, more floriferous vine. Before setting outside in late May or early June, repot and apply a water-soluble fertilizer. Do not set outside until all chances of frost have passed and temperatures stay above 60 degrees F.
Brugmansia or Angel's Trumpet is another popular tropical. It has monstrous fluted flowers that are very fragrant after dark. They are great plants for patios. They can grow to 4-6 feet tall but can be pruned vigorously to easily grow in a large container. During active growth in summer brugmansia appreciate lots of water and fertilizer.
Brugmansia can be wintered much the same way as mandevilla in a cool place or grown as a houseplant. Like the mandevilla, you may be watering only once a month once the plant goes dormant. When its dormant, brugmansia lose all their leaves and look dreadful. Just ignore it.
When the brugmansia sends out new shoots from the woody stem in early spring, than start watering and fertilizing. It will quickly explode with new growth. Wait until after all danger of frost has passed before setting brugmansia outside.
Tropicals are worth the extra effort to nestle them in for a long winter's nap.
Idea Garden Workshops start at 10:00 am. No fee or registration is required. September 30-Making Gardener's Black Gold:Compost.