When planting subtropical and tropical plants in a place like New Orleans or Tampa, you simply throw them in the ground where you like, and walk away. That’s not to say you can’t try to push the limits of a zone 9b nearly tropical climate, but there is vast array of palms and other plants available makes it easy to have a tropical scene with little effort in such a place. In Memphis, however, some planning and finesse is necessary. Our list of palm options is limited. Our subtropical and tropical selection is fair, but we have to make do with less.
With this being the case, one of the best things you can do for your subtropical garden is to properly plan where you will situate your plants. The basic points to consider are: wind, water, walls, and sun. Memphis has a rather harsh climate for plants to deal with. It is very wet in our rainy season from November to April. It is very parched in our dry season from July to October. We get quite hot from May to September, but yet very cold for our latitude in January and February.
So, with these things in mind, before you buy or are given a plant, check for the plants particular requirements. This goes for temperate plants as well. Since the main topic of this website is subtropical gardening, we’ll start with the best way to site plants that are sensitive to the cold. Two of the main points of siting here are wind and walls. Take for example a zone 8 palm like the Sabal palmetto or a Pindo palm. Even when Memphis has a zone 8 winter, our cold duration can still be longer than a coastal zone 8. The winds out of the North will also strip the heat and water from a palm during cold events. As a result, planting marginal palms and other sensitive plants on a South facing wall of a home or building will do two things. First, it will eliminate desiccating cold north winds. Secondly, south facing walls absorb heat during the day and release it back during the night. This can mean a temperature boost of several degrees and a palm or other plant that is not losing vital water. On the coldest two or three nights of winter, a few degrees and protection from wind can be the difference between life and death or between a plant simply surviving or truly thriving.
Sunlight is another aspect to consider. Afternoon sun in the summer time is brutal. Some tropical plants, like cannas, will do just fine in full sun. But they can do even better with sun in the first half of the day and shade in the latter half. This allows them to get good photosynthesis, but not so much sun that they lose too much water and get over stressed as the ground around them bakes. Palms such as the Needle palm enjoy a good deal of shade, as is there native environment of swampy woodlands of the Southeast. They can handle full sun, but obtain a really robust look when part of their day is shaded. In Memphis, the windmill palm is another that does fine in the open, especially when well watered, but really likes some relief from all day sun. Being a truly temperate palm, they do not need blisteringly hot temperatures to grow well. They prefer mild maritime climates like the Pacific Northwest. So some afternoon shade and frequent watering will make a windmill palm really look its best in Memphis.
On the topic of water, make sure that the palm or plant you are siting will receive the amount of water it wants. This works both ways as some palms and succulents really don’t like much water at all. Or they like some water, but cannot tolerate having wet roots. Saw palmettos and European fan palms are good examples of plants that must be planted in full sand and in a raised location. Another aspect of water requirements that is often overlooked in Memphis is winter rainfall. Our winters are horribly wet and nasty. For herbaceous plants like cannas, bananas, and gingers, sitting in lowlying areas where water pools is a guaranteed death sentence. Plant such plants in beds that are at least a few inches above the winter water table. The bulbs and roots need to stay dry enough that they don’t rot before spring arrives.
One last point to consider when planting sensitive plants is tree canopy. Believe it or not, planting something sensitive under a tree, even one that is deciduous can go a long way to saving the plant from extreme cold events. On crystal clear nights in winter with no cloud cover, heat from ground sources radiates quickly into space. Take notice of grass beneath trees and you’ll see that it generally stays greener while grass in open sections of yards will be browned out. Tree canopy protects plants from this radiational freezing. Tender shrubs like oleanders and camellias benefit in our area from not sitting totally exposed to the night sky on winter nights.
So what’s the very best place for a marginal palm in Memphis? Ideally, you’d put it on the Southside of your home a few feet from the wall, under a huge oak, in a raised bed. Fortunately, we do have several options that don’t need such intensive planning and care. There are plenty of things we can just slap in the yard anywhere we like and watch it thrive. For the ones that need some help, proper siting will go a long way.