Memphis is a city of large trees. These include the many trees in the Quercus genus (Oak), trees in the Ulmus genus (Elm), trees in the Ginkgo genus (Maidenhair), the Planus genus (Plane and Sycamore), the Liquidambar genus (Sweetgum) and other giant plants that dominate the Memphis landscape. When you fly into Memphis International Airport, if you can pull your eyes away from the spectacle of the pyramid, and if you ignore the warehouses around the perimeter, you can see that we have one of the densest canopies of any city in North America.
Of course, big shade trees provide us with a lot of benefits. They cool the areas underneath them, reducing our utility bills, and they provide shelter for wildlife and other plants. They also deflect water, reducing erosion. But, they leave landscape designers, and home owners without irrigation systems, a bit of a problem. That problem is dry shade.
Over the years, I’ve tested a lot of plants and discovered some that do well in these conditions. But, even with the right plants for dry shade, you will still need to water, beginning the last week of May, through the end of September, if your plants are going to do well. What I can offer you is not plants that will never need watering, but rather, plants that will need less supplemental watering. Moreover, any plant, no matter how drought tolerant, will need more water during its first two years, its establishment period, than in subsequent years.
An Under-Canopy Tree
So, let’s first begin with an under-canopy tree. Cercis canadensis ‘JN2’ (The Rising Sun Eastern Redbud) is one that, arguably, has not yet proven itself. However, it shows great promise as being significantly drought tolerant. You may recall that I mentioned this tree in my last column because Eastern Redbud, generally, is a host plant for certain butterflies, Callophrys henrici (Henry’s Elfin) in particular. But, whereas most Eastern Redbuds prefer full sun (more than 8 hours of sunlight) to part sun, the Rising Sun cultivar can handle part shade. Since Eastern Redbuds, in general, are known for drought tolerance, it is probable that this cultivar, in addition to tolerating shade, will also tolerate relatively dry conditions. Like all Eastern Redbuds, it gets rosy pink to purple blooms in early spring, before leafing out. But, what makes this cultivar special, in addition to its shade tolerance, is its diminutive size and its leaf color, ranging from bright orange to deep gold, to speckled green.
Second, the single most drought tolerant ground cover for part shade (4-6 hours of sunlight) to full shade (2-4 hours of sunlight), that I find attractive, is Pachysandra terminalis ‘Green Sheen’ (Green Sheen Japanese Spurge). Though it gets tiny white flowers in early spring, it is well-liked because it forms a consistently bright green ground cover in dry shade, where few other plants can succeed. Though technically a perennial, in most years in Memphis it will be an evergreen.
Low Growing Color
Third, the best source of low growing color that I have seen for dry part shade or dry full shade in Memphis are plants from the Heuchera genus. This genus has many species, some native to North America and some not, represented in the nursery trade in the many varieties, cultivars, and hybrids
readily available at good garden centers. Commonly known as “Coral Bells”, some of my favorite choices of Heuchera include Heuchera villosa ‘Autumn Bride’, Heuchera hybrida ‘Berry Smoothie’, Heuchera villosa ‘Caramel’, Heuchera hybrida ‘Electric Lime’, Heuchera hybrida ‘Cherry Cola’, Heuchera hybrida ‘Green Spice’, Heuchera hybrida ‘Glitter’, and Heuchera hybrida ‘Stainless Steel’. With hundreds to choose from, and no garden center able to carry them all in any given year, it is definitely a collectible plant. Remember, in their native environments, Heuchera are found on shaded slopes. So, they will not tolerate poor drainage. Additionally, though Heuchera are routinely hybridized with plants from a closely related genus, Tiarella, the resulting hybrid, commonly termed a Heucherella, may not be quite as drought tolerant.
But, there are some other great perennials that, though not quite as drought tolerant as Heuchera, are still pretty drought tolerant. The most well-known of these are plants from the Hosta genus,
my favorite being Hosta with blue leaves, like Hosta elegans and Hosta hybrida ‘Abiqua Drinking Gourd’. Like the Heuchera, plants from the Hosta genus are highly collectible, numbering in the hundreds. In fact, one of the most well-known plant groups in Memphis is the Memphis Hosta Society, its size and strength a good indication of the utility and power of the genus.
Other perennials for dry shade that I like include: those from the Epemedium genus, like ‘Orange Queen’, ‘Frohnleiten’ , and ‘Sulphureum’; Polygonatum odoratum var. pluriflorum ‘Variegatum’ (Variegated Solomon’s Seal), and Iris cristata (Crested Iris). These, typically, would handle part shade better than full shade, unlikely to bloom in full shade.
Finally, if you absolutely must have some evergreens for your dry shade area, I have had good luck, in part shade, with everything in the Mahonia genus, Taxus x media ‘Densiformus’ (Dense Spreading Yew), and Cephalotaxus harringtonia ‘Prostrata’ (Japanese Spreading Plum Yew).
Again, just keep in mind, even the most drought tolerant of plants will still need some supplemental irrigation in Memphis, 1-3 times per month, from late May to late September. Also, remember that good planting technique, the right soil amendments, good plant nutrition, good watering technique, and planting at the right time of the year can dramatically improve any plant’s drought tolerance, as covered in other columns of mine.
The author, John Jennings, is Palladio’s Manager of Horticulture. John is an ISA Certified Arborist and is licensed to apply chemicals for horticultural purposes in Tennessee. John also writes the Garden Variety Column for Memphis Magazine. If you have questions or comments about this article, or any other horticulture related topic, please reach out to him by email at firstname.lastname@example.org. Most days, he can be found in or near Palladio’s horticulture building at 2231 Central Avenue, Memphis, Tennessee 38104.