Overwintering Tropical Plants
If you want a back yard or deck next spring that is reminiscent of Key West or a Jimmy Buffet concert, you need to correctly over winter your tropical plants, said Greg Stack, a University of Illinois Extension horticulture educator.
“In order to protect the investment you made this spring in your tropical plants, which sometimes cost as much as more permanent perennials and shrubs, take a little time to see how you can successfully and easily over winter these garden gems,” said Stack.
“The use of tropicals in home gardens as points of interest, color, texture has increased dramatically. Many garden centers now offer a much larger selection of some very exotic-looking plants.”
The most commonly used tropicals such as elephant ear, palms, cannas, hibiscus, ferns, angel trumpet, and caladium really enjoy Midwestern summer, he added.
“It gets hot and humid and with ample moisture these plants can grow to impressive size,” he said. “So what do you do with them when it gets cold and threats of frost start to show up in the weather forecast?
“You round ‘em up and bring them in.”
But most gardeners are usually not going to have the space or right conditions to physically dig these plants up, bring them indoors, and maintain them over the winter, Stack admitted.
“Some plants like the elephant ears and palms can tolerate the lower light indoors but the majority prefer greenhouse conditions to really look good,” he said. “So, what are the alternatives?”
Many tropicals such as elephant ear, cannas, and caladium form tubers, bulbs, or corms. These underground structures can be successfully over wintered and then replanted next season, he said.
The best time to dig up these bulbs, tubers, and corms is in the fall right after a light frost has turned the leaves on these plants a little brown. This tells the plant it is time to go dormant. After this happens, cut the stems back to about six inches and carefully dig the plant up.
“There are several methods for storing these dormant bulbs and no one way is better than another. It is more of what works for you,” said Stack.
One of the more successful storage techniques includes washing the soil from the bulbs and allowing them to air dry. Many of these bulb-producing tropicals will have produced many bulbs over the summer that can be separated prior to storage.
“This is a great way to increase your stock of tropicals and have a really tropical backyard next year,” Stack noted.
Once dry, place the bulbs in containers that are well-ventilated such as milk crates, bread crates, or similar containers. Pack the bulbs with peat moss, small bark chips, or sawdust. This material helps to hold just enough moisture to keep the bulbs from shriveling.
“The bulbs now need the right climate to make it through the winter,” he said. “Place the crates in a dark place where the temperature is around 40 to 50 degrees. Basements, cellars, and crawlspaces work great. Check on the bulbs monthly to look for signs of rotting or shriveling. Discard the rotten bulbs and spray the shriveled bulbs with a little water to get them plumped back up.
“Storing the dormant bulbs this way will allow you to get a jump start on spring. Re-pot the bulbs about six to eight weeks before the last frost in your area. Doing this allows you to get a larger, fuller plant for your tropical garden much earlier in the summer.”
Tropical hibiscus is a very common and popular tropical plant. Potted specimens can be found at almost every garden center in the spring. Hibiscus is often used as a container garden plant.
“While they can be brought in before the first frost and maintained as a growing plant, the results are often not terrific,” Stack said. “Because these plants demand such high light, the foliage soon turns yellow and falls from the plant. The flower buds also tend to fall off before they open.”
Stack suggested an over wintering alternative for hibiscus.
“Bring the containerized hibiscus indoors before frost. Don’t water and allow the soil to go dry,” he said. “The result will be that all the leaves will fall off the plant. This is good because now the plant has gone dormant. Place the plant in an area that is around 40 to 45 degrees. Check on the soil moisture about every two weeks and if the soil is dry two to three inches down in the pot, add a small amount of water. This will keep the stems from shriveling but not encourage new growth.”
Angel trumpet is over wintered the same way, he added. Both are plants that get better with age. By carrying over plants from year to year they get larger and make very impressive and imposing specimens in the garden.
“In the spring, bring the plant into a warmer, well-lighted area, water well, and prune back lightly,” he said. “In a few weeks, you should have a newly revived plant ready for the garden.”
Bananas, he noted, are great conversation pieces in the garden. But what do you with a banana that might be eight to 10 feet tall during the winter months?
“The answer is simple: cut it down,” said Stack. “Bananas are the easiest tropicals to over winter. If the banana was grown in a container, cut the plant down at pot level right after a light frost darkens the foliage.
“Move the container to a dark area in a 40 to 45 degree temperature, and keep the soil on the dry side. As spring approaches, you’ll see a new shoot coming from the center of the cut stump. That is your new banana. After the threat of frost passes, put it back outdoors and with plenty of moisture and fertility that once small banana will grow to immense proportions.”
If the banana was growing directly in the garden, however, dig it up but don’t cut it back. Wrap the root ball in a black plastic garbage bag and store it just like you would a containerized plant. In the spring, cut it back to about four inches above the root ball, pot it up, and start your new banana growing.
“No matter how you choose to over winter your tropicals, you will be rewarded with having larger, more imposing specimens as well as more of them when you start to divide those that produce bulbs and offshoots like banana,” Stack said.