Add color to your garden this summer with tips on selecting and caring for tropical plants from Master Gardener Janet Carson
by Janet B. Carson
Summer in Arkansas has people rushing to get indoors to the air conditioning, but our plants have to deal with whatever comes their way. Some plants actually thrive in heat and humidity and bloom all summer long. What more could a gardener want? If you like bright, bold colors that can stand up to heat and humidity, then you need some tropical flowering plants.
Tropical plants thrive year-round in the warm, humid environment of the tropics, and right now it feels somewhat tropical outside in Arkansas! A wide range of tropical plants, both foliage and flowers, are available at nurseries and garden centers statewide. Tropical plant choices continue to grow each year, and we have options not only in the color of blooms but also in the size of plants.
Mandevilla (also called dipladenia) is a beautiful and highly popular tropical flower that seems to be everywhere this year. The original mandevilla available in our market years ago was a vigorous vine with vibrant pink blooms. While that variety is still an option, through plant breeding, we now have many more choices, including plants with various shades of pink, red, white, yellow and even apricot-colored blooms. Some have variegated foliage and bi-color blooms. The plants can be prolific vining plants like the original, or more compact and bushy. Know which mature size you are looking for and look at the tags in the pots to see what is being offered. The compact ones actually make nice bedding plants in the ground or can be grown in containers. They all thrive in full sun and bloom from frost to frost.
One of the most common tropical plants is the flowering hibiscus, which comes in a wide range of colors and sizes. Make sure you know the difference between the tropical hibiscus and the hardy perennial hibiscus. Tropical is not hardy, while the perennial form comes back each year. All hibiscus plants are in the mallow family. The tropical or Chinese hibiscus, known botanically as Hibiscus rosa-sinensis is native to tropical Asia. They have leathery, glossy leaves with some varieties having variegated foliage. Depending on the variety, flowers can be single or double with colors ranging from white, yellow, orange, pink and all shades of red with single colors or multi-colored blooms. Each flower only lasts one day, but given plenty of sunlight and ample nutrients, these plants can produce enough buds to give you flowers all season long provided they get full sun, ample moisture and regular feedings. The hardy, perennial hibiscus has thinner foliage (shape can vary by species) and typically larger, almost dinner-plate size blooms. The perennial form usually blooms late June through August on woody stems. There is a finite season of bloom for these plants. Once we have a frost the stalks die back to the ground, but the plant regrows from the soil line the next spring.
Bougainvillea is another older tropical plant, often sold in hanging baskets. The true flower is the tiny white bloom inside the colorful bracts (modified leaves) which can be pink, red, yellow or orange. They usually do best if given limited root space. If you give them a large container, they spend too much energy growing foliage and roots which can limit the flowers. Do be aware that there are small thorns along the stems. Again, the more sun they get, the better they flower.
Ixora is a newer introduction of tropical plants. The plant is an evergreen shrub in tropical climates, but it makes a fantastic container flowering plant that will bloom non-stop all summer long in Arkansas. The flowers come in shades of orange, red or yellow. It will do well in a container or planted as a summer annual in the ground. It will not survive our winters outdoors.
Plumeria, the fragrant flower associated with Hawaii, is beginning to bloom now. The showy blooms come in a range of colors, and the plants are fairly drought tolerant as well. They can grow quite large if you give them winter protection each season. While the plants are not hardy, they are easily stored in a garage or inside the house for the winter months.
While we love the color we can achieve with tropical flowers, there are also some outstanding tropical foliage plants. Bananas, both standard and dwarfs, give a tropical look, along with palms, colorful crotons and a whole line-up of houseplants. If you move your houseplants outside for the summer, consider placing them amongst your shrubs and garden plants to add an extra dimension of color and form for the summer. It also makes for easier watering if you have a sprinkler system.
As the name implies, tropical flowering plants are just that—tropical, and can’t survive outside year-round in Arkansas. Some gardeners allow Mother Nature to take her course, and they add their plants to the compost pile after a frost, choosing to buy new plants every year; while others move them to a protected spot for the winter—either in a garage, basement or inside. If you do overwinter your tropical plants, they need a severe haircut the following spring.
Tropical flowering plants bloom on the new growth each season. Older, root-bound plants in containers don’t grow very much. If the plants aren’t putting on new growth, they won’t put on new flowers. Pruning the plant back by half or more its size and repotting it when you move them back outside in the spring will encourage rapid new growth and plenty of flowers. When repotting, you don’t have to up the size of the container, but you do need to lighten the root load. Shave off some roots on all sides of the root ball, shake off the old soil and add fresh soil to the same pot. This will encourage more growth.
Regular fertilization will also keep your tropical flowering plants flowering. If you have planted them in the ground, fertilize every two to three weeks. Plants grown in containers will need more regular applications of fertilizer. As temperatures heat up, water needs increase. Containers have a finite amount of space, and the soil dries out quickly. Frequent watering leaches nutrition out of the soil. Depending on the size of the container, daily watering is often needed during the hottest, driest times of the year. Frequency of watering will depend on the size of the container, the size of the plant, how exposed the plant is, the temperature and natural rainfall. To keep your plants in constant bloom, fertilize often – every week or two with a water-soluble fertilizer or less frequently with some of the slow release types. Make sure the plants are well watered before you fertilize so you don’t burn them, especially if there are high temperatures.
Pests are not common on tropical flowers, but they can occur. The more common insects include aphids, white fly and spider mites. Monitor your plants and control as needed. If you do plan to overwinter your tropical plants indoors, be sure to carefully inspect them prior to bringing them indoors for the winter.
You don’t have to live in the tropics to enjoy tropical plants, and luckily we have easy access to them. If your garden needs some extra color now, choose tropicals. Even if you can’t stand the heat, they can!