Overwintering tropical plants is economical and rewarding
By Mary Fran McClure
WSU Chelan/Douglas County Master Gardener
Salvaging expensive plants always gets my vote. Many tropical plants can be saved year-to-year by overwintering in an enclosed garage or area that doesn’t freeze.
Yes, those lovely tropical mandevillas and cannas you see lining garden store shelves during spring and summer can be saved. An added plus is how much larger these plants will develop with year-to-year growth rather than starting from scratch every year.
On the other hand, I don’t try to save my sweet potato vines because buying little starts next spring is economical, and they grow quickly.
These steps are how I save my mandevilla vine and cannas.
Popular mandevillas sold locally generally have either red or white trumpet-shaped flowers. They bloom all summer and well into fall, definitely making them an attractive vining plant that deserves attention. Native to Central and South America, this woody-stemmed climber does well on a pergola or trellis to show off its blooming profusion all summer and into fall.
It prefers warm temperatures but not hot; it’s best located with morning sun and afternoon shade. My vine faces east with at least six hours of morning sun and then afternoon protection next to the garage. This also provides some wind protection.
Plant in quality, well-drained potting mix for long-term care. Use a large container but one that can be moved. I have left my healthy mandevilla in the same mix and it seems happy with doses of light fertilizer during the growing season. Water whenever the soil begins to feel somewhat dry.
I’ve saved my three- or four-year-old mandevilla by simply moving it into the garage for overwintering in late October, before heavy frosts.
The other tropical plants I overwinter are cannas that I grow in large pottery containers. After a light frost, I move them, pot and all, directly into the garage. I cut off foliage and allow the rhizomes to just hunker down for the winter. A light watering not more than once a month seems to keep them healthy. Less water is better than too much, which can cause mold and decay. Too much water and too frequently is the most likely culprit for damaging the rhizomes.
The real trick in overwintering these tropical plants is not overwatering while they’re essentially in a state of no growth.
You can either dig and divide rhizomes when you’re moving them into storage or wait until early spring when a few new sprouts begin appearing. I carefully separate those rhizomes, saving the new healthy ones and repotting them in containers. They prefer warm soil, so if planting outside, put them in a protected, sunny location and wait until the soil warms. Cannas like conditions similar to tomatoes; they’re laggards when put out in cool weather and need warm temperatures to thrive.
Once we have warm weather, cannas provide interesting leaf patterns as well as spikes of colorful blossoms all summer.
Is this the year for you to try overwintering your tropical beauties?
A WSU Chelan and Douglas County Master Gardener column appears weekly in The Wenatchee World. To learn more, visit bit.ly/MGchelandouglas or call (509) 667-6540.