Before coming to St. Louis, I was the director of Mercer Arboretum and Botanical Garden in Houston. There, we could grow many of the wonderful plants of the Deep South—tropical ginger lilies, Louisiana iris, evergreen daylilies, citrus, michelias, and fabulous aroids. We would haul the most tender ones into a polyhouse for 90 days in the coldest part of the year, but many wonderful tropical plants would overwinter for us there. I miss that lushness, but Julie and I have sought out ways to enhance our summer garden with many bodacious tropicals.
Coleus, vinca, impatiens, caladiums, petunias…so many of our favorite ‘annuals’ are really tender tropical perennial plants. Julie remembers deplaning from the puddle jumper the first time she went to the Bahamas and admiring the colorful hedge lining the tarmac. When she got closer, she realized that the colorful sheared, woody hedge was actually coleus! Our frost-sensitive bedding plant is a full fledged shrub in the tropics. The same is true of poinsettia. They can reach 18 feet in the right place. What we consider tropicals—bananas, palms, ’houseplants’ in general—are a rapidly changing group of plants as they are being selected and bred for new colors, shapes, sizes, and hardiness.
Must Haves - Musa
Julie and I both share a passion for banana. Quick growth and very bold foliage make them show stoppers in any summer garden. Two genera, Musa and Ensete, are readily available commercially. Musa is the genus that bears the fruit we think of when we hear the word ‘banana.’ It tends to grow as a tall central stem that sheds its lower leaves as it increases in height, giving it a palm-like look. Eventually, it will surround itself with new basal shoots called pups. The genus Ensete retains all the lower leaves as it grows, making it a much larger, heavier plant in the landscape. The two most common Ensetes in the trade are E. morelii and E. ventricosum, both of which have very striking red highlights on the leaves and/or midribs.
Another fruit that has great ornamental cultivars is the pineapple, genus Ananas. But beware—some varieties have razor sharp spines all along their leaf margins that can slice through leather garden gloves. Ananas ‘Smooth Cayenne’ has spines only on the tips of the leaves. It makes a great houseplant and actually will produce fruit as a potted plant. Botanically, pineapples are actually bromeliads. These epiphytes are popular as indoor foliage plants with rosettes of leaves. A great project for a child is to take the top off a grocery store pineapple, dry it out for a couple days, then root it for a new houseplant. Easy!
Brugmansia, or angel trumpet, is an elegant showstopper. Ranging in height from 5- to 10-feet-tall or more, they produce large, hanging flowers stretching as much as a foot long each. Whether in the ground or a pot, make sure they’re planted near your outdoor entertainment area because the flowers release their best fragrance in the evening. One of our volunteers has had a Brugmansia in a pot for almost a decade. It is a member of the Solanaceae family, along with peppers, tomatoes, and tobacco, and is often confused with the similar forms of Datura, or Jimson weed. An easy way to separate the two trumpet plants is that Datura flowers point skyward and Brugmansia flowers hang down. All parts of this plant contain seriously poisonous alkaloids, so watch children and pets around the pretties.
‘Elephant ears’ is the catch-all term that includes several genera of aroids including Alocasia, Colocasia, Xanthosoma, and Caladium with broad, often colorful spade-shaped leaves. Ranging in size from the cute little caladiums you buy as bedding plants to the 10-foot-tall Alocasia ‘Borneo Giant,’ this family provides some of our best, bodacious tropical garden forms. Foliage colors range from the almost pure white of some caladiums to the dark purple-black of Colocasia cultivars. It is an incredibly diverse and useful family of plants for the summer garden. While many aroids can make a wonderful focal point in a container, some get so large they need to be in the ground for balance where they can tower over everything around them. And while many of them benefit from some afternoon shade—they are, after all, from the jungle understory—there are those, including some Caladium varieties, which may thrive in the full sun, heat, and humidity of a St. Louis summer.
One of Julie’s favorites is Xanthosoma ‘Lime Zinger.’ A bulb that has only been around in the trade for a few years, we save them from year to year, storing them indoors, over winter and planting them outside each spring, where they can reach heights of 5 feet or more in a month or two.
There are several plants that we think of as tropical that actually have varieties that are winter hardy here. Zantedeschia, or calla lily, can be hardy here. Truly popular in Mexico, callas love wet situations and can grow in standing water. Jason Delaney, the Missouri Botanical Garden’s resident bulb master, says there have been several clumps of callas in our bulb borders for years. The varieties Z. ‘Black Forest,’ Z. ‘Picasso,’ and Z. ‘Sunshine’ all do well in St. Louis.
Crinums lilies are actually not lilies, but members of the amaryllis family. Jason says that C. bulbispermum and its hybrids—x Powellii and x herbertii—are winter hardy here. They have lush, strappy foliage up to 4 feet long and amaryllis-like flowers. In the fall, the dying foliage acts as its own mulch, helping to protect the bulb from cold. Any of these ‘are you sure that it is hardy here?’ plants will benefit from a heavy layer of mulch in the winter.
Gingers are beautiful, upright plants with cane-like stems that can reach up to 6 feet. Zingiber officinale is the source of the spice ginger, made by grinding up the rhizome. There are several lovely foliar variegations of this plant, including a bright white form and one with bright, bold yellow leaves. Alpinia, or ginger lily, is a close relative.
Lemongrass, Cymbo pogon citratus, is the same aromatic grass used extensively in Asian cooking. As an annual here, it makes a bright green clump of grass up to 6 feet tall that stays fresh and clean looking all summer, thriving in our hot, humid weather. The leaves are very aromatic and the bulb-like base, thinly sliced, is used for Thai and Vietnamese cooking. Grown as a row crop for production of the essential oils used in perfumes, flavorings and medicines, it is closely related to the grass used for making citronella, the natural oil used for repelling mosquitoes. Buy a bundle of lemongrass stems and root them in your kitchen window for transplanting outdoors later.
Manihot esculenta ‘Variegata,’ variegated tapioca plant, is another of our favorites, with beautiful green and yellow palmate leaves dangling from red petioles on butter yellow stems. It can become a lovely, full ‘shrub’ in the course of one season outside, but needs to be taken inside for the winter. Of course, as soon as you take it inside, it will sulk and lose all its leaves. It will recover eventually, and next year you’ll have an even better display. This little beauty is one of the leading food crops in the tropics, with the processed root providing cassava flour and tapioca.
You will never know exactly which plants your own microclimates will support. The difference between a city garden and a country garden, which would be just 30 miles in St. Louis, is almost half a zone. The heat sink of the city, plus walls to hold heat and buildings that block the wind, can create small, sheltered areas that preserve amazingly well some of the borderline tropical plants. The world of tropicals is rapidly evolving. There are new and wondrous varieties appearing every year. Poke around that little family-owned garden center down the block. Chances are someone working there is a bonafide ‘plant geek’ who loves finding something unusual and being the first in the area to present it to the public.
Learn your own space. Test it. My classmate from NC State, Tony Avent, likes to say, “I don’t know that I can’t grow it until I have personally killed it three times.” Sometimes the most important thing is finding the right planting spot. Happy digging!
For more information on overwintering bananas: mobot.org/gardeninghelp/plantfinder/Plant.asp?code=C539