The St. Lawrence River Valley, west of the Adirondack Mountains, is a far cry from the Piedmont Plateau of north and central Georgia. The gardening knowledge I picked up at the knee of my parents and grandparents hasn’t been much help to a transplant like me. Here in Atlanta, Georgia, the crocuses and daffodils start blooming in February. There, it isn’t unheard of to have a snowstorm in early May.
Fortunately, a friend introduced me to the Georgia Native Plant Society (GNPS). This organization, much like those in other parts of North America, was founded to educate the public regarding the preservation of our native plants. By encouraging the rescue and propagation of plants taken from the path of immediate development, GNPS discourages wild collection, and provide native plants for use in home and public gardens, including school projects and restoration of public lands.
Over the years of my association with the society, I learned some basic characteristics that make gardening in this part of Georgia different from other places I have lived. Between one third and one half of our soils are clayey, with the balance consisting of gray sandy soils, and due to extreme changes to the land from agricultural activities, mature climax forests (more than 150 years old) are rare and virgin forests are virtually non-existent.
Most importantly, the underlying rock of much of the Georgia piedmont causes the soil to be acidic. By way of example, a test of the acidity of lawns in Georgia conducted in 1984 found that 30% had a pH of 5.4 or below (strongly acid), 28% were between 5.5 and 5.9 (moderately acid) and only 42% fell in the range of 6.0 and above (slightly acid). Add to this research, which concludes that acid rain has accelerated natural soil acidification, and it is clear that learning about acid loving plants is a smart investment wherever you live.
A few of my favorite acid lovers are profiled in this article. Several of these plants (including Sourwood, Mountain Laurel, Trailing Arbutus, Piedmont Azalea, and Blueberry) fall into the Ericaceae or Heath family, which are the first plants to come to mind as acid lovers.
Sourwood Oxydendrum arboreum
Each year, the GNPS selects one plant native to our state to be honored as plant of the year. In 2004, the membership voted for Sourwood, a small to medium sized tree. Appropriate as a focal point in southern gardens, this tree provides multi-season interest.
After the usual spring show of flowering trees and shrubs, the Sourwood offers its pretty summer blooms – cascades of white bell-shaped flowers. These flowers give the tree one of its many common names, the lily-of-the-valley tree. One of the first trees to begin the fall color show, it continues to offer interest well into the winter. Attractive fruit, which matures during September and October, remain on the tree to disperse seed from the open capsule throughout the winter. Further Sourwood possesses a distinctive bark that is gray, tinged with red, deeply fissured, with narrow, scaly ridges especially at the base.
Though the tree has been known to reach 60 feet, and one rare specimen found in 1982 by the Ohio Forestry Association in Vinton County, Ohio was measured at 75 feet, generally it is much smaller.
Also known as sorrel-tree, sour gum, or elk tree, its flowers are an important source of honey in some areas. Sourwood is among the latest of the flowering shrubs and trees to bloom, and is a great source for honeybees, as most other trees are spring bloomers.
“A slow grower, the Sourwood might not seem a natural choice for homeowners, but the patience it takes to establish this southern classic will be rewarded with a truly distinctive year round beauty in the landscape,” said Mary Tucker, who manages the plant of the year program. Though difficult to transplant, the Sourwood is available from select mail order and online nursery sources, and is native throughout the South, Southeast, Mid-Atlantic and Eastern Mid-West states. It is advertised to be suited for zones 5 to 9.
Oakleaf Hydrangea Hydrangea quercifolia
Selected
as Alabama wildflower in 1999 and the GNPS Plant of the Year in 2000, the Oakleaf Hydrangea is another native for year round enjoyment. Pale gray green leaves emerge in early spring, and are soon followed by large creamy cone shaped flower clusters. As the blossoms age, they shift from light pink through rosy tones to a final tan. These clusters hang onto the plant well into late fall and early winter. The leaves provide interest as well. Large and reminiscent of oak-leaves, these turn to rich reds, purples and burgundies in late fall and often remain on the plant through November and early December. In winter as the blossoms and foliage finally fall, the interesting structure of the branches, accented by colorful exfoliating bark provides a pleasing accent. Unlike Bigleaf hydrangea H. macrophylla these blossoms do not change color based on soil pH.
Planted in moist, well-drained acid soil in part to full shade, these plants are quite drought tolerant once established, and work well in the landscape in the shrub border, as a specimen or massed at the edge of a wooded area. Expect properly sited plants to reach a height and spread of eight feet or more. Especially in warm climates, it is important to ensure plants are shaded from afternoon sun. Native only to a small region of the Southeast, many Oakleaf Hydrangea cultivars are sold as hardy to zone 5. However, Michael A. Dirr, a professor and well known horticultural author from the University of Georgia, tells us you might expect some dieback and winter kill of flower buds with extended temperatures of minus 20 degrees F.
Mountain Laurel Kalmia latifolia
The state flower of both Connecticut (adopted in
1907) and Pennsylvania (adopted 1933), the Mountain Laurel is found throughout Eastern United States, and as an exotic in Quebec and is sold as hardy from zones 4-9. This evergreen shrub can be difficult to transplant. However once established in a proper site with moist well-drained acid soil (4.5 to 5.5 pH) and part shade to full sun (consider a north or east-facing slope, which limits the afternoon sun for southern climates), mature plants can reach five to twelve feet tall with a similar spread. The more recent ‘elf’ variety can be expected to achieve only three feet.
One of the more colorful names for this evergreen shrub is Calico Bush. So named for the pink edged white blossoms produced in terminal clusters four to six inches across, creating an image reminiscent of calico fabrics.
Mountain Laurel is extremely toxic in all its parts to humans and livestock and other animals. In fact, one study suggests that when eaten by Canadian pheasants the poison is communicated to those who feed on the birds.
On rescues, a common companion plant is Trailing Arbutus Epigaea repens. This plant is a rare evergreen groundcover blossoming in late winter with pale pink flowers. Both plants can be finicky to transplant from the wild. For the Trailing Arbutus that I recently acquired from a rescue, I was advised to add ground up ferrous sulfate tablets (1-2 per eight inch planting) to the soil to increase acidity.
Piedmont Azalea Rhododendron canescens
In 1979, the native azalea was chosen as Georgia's state wildflower, and many species and varieties are found across Georgia. In fact, there are some thirteen species of deciduous azaleas native to the state. Additionally, due to overlap of distribution and blooming season, we see many interspecific hybrids along with introgression (when a hybrid back breeds with one parent species only resulting in plants that generally look like one species but have some genes of the other). This can make species identification a significant challenge.
While the Great Rhododendron Rhododendron maximum, also profiled in this issue, is native to Georgia, I want to talk about one of our most stunning natives – Piedmont Azalea Rhododendron canescens. The earliest blooming of the native azaleas (March and April), this deciduous shrub is well known for its vivid display of pink or white, fragrant clustered blooms.
Selected by the GNPS as our 2001 plant of the year, is also sometimes misnamed as Wild Honeysuckle, but our Piedmont Azalea has little in common with the West Coast native. You may also find this plant listed as the Florida Pinxter Azalea, and though typically considered a southern species, it is hardy enough to see wider landscape use. Commonly available from native plant nurseries, this prominent plant is often rejected by others in the belief that gardeners will not purchase deciduous azaleas.
Piedmont Azalea makes a spectacular spring show since the flowers open before the leaves have expanded. A mature plant can be expected to grow to ten feet and more with an upright habit. Rich, moist acid soil in light shade, but receiving some direct sun, or high filtered shade, as found under tall trees or at the forest edge and on stream banks, form an ideal environment.
When attempting to rescue these plants, it is important to know that the root system is not deep, but includes many far-reaching lateral runners. Saving as many of these runners as possible is critical to success. Also, local experts recommend soaking the plants overnight in a tub of water to counteract shock, and reducing the foliage by one third prior to transplanting. This can be done by clipping every third leaf in the cluster, or by removing the tips of all leaves – a daunting process with larger plants. Typically, the smaller the plant the easier it will be to dig and transplant.
Low Bush Blueberry Vaccinium pallidum
Also known Hillside Blueberry, a synonym for this deciduous shrub is Vaccinium vacillans. One of the identifying characteristics of this plant is the pale backside of the leaf. It is present throughout the Eastern and North Central United States and Ontario, and the fruit provides a valuable food source for many small birds and mammals. Though the berries are sweet and can be used in pies and jellies, it ripens over a long period of time, causing collection in quantity to be difficult. Native Americans dried the berries and pounded them together with strips of venison to season their pemmican.
I rescued a number of these plants from a site in Snellville, GA, which is being developed. Like the Piedmont Azalea, this low growing shrub exhibits many longer runner roots, and it is helpful to preserve as much of this root system as possible. Despite care in collection and the overnight soaking method mentioned above, by day two I was doubtful that any would survive. However, following advice to prune the plants hard, they all re-sprouted and are shaped up as healthy specimens.
The site of this rescue included a dry sandy hill that was covered in the one to two foot tall plants under high dappled shade. For the home landscape, ensure well-drained acid soil – down to 4.5 pH – and at least partial sun.
Pretty bell shaped green-cream to pinkish flowers appear in early spring. I dug the plants mentioned above in the first week of April and the colony had nearly finished blooming. Around the same time, an important pollinator in our region, the Southeastern blueberry bee, starts flying. Elaine Nash, an active member of the botany community in Georgia, tells me that this bee “pollinates 100 % of Carolina Jessamine and a wide variety of other native plants. Since the drastic decline of honeybees, those plants in my yard that bloomed before the earliest blueberries, like Japanese Pieris, don't get pollinated.”
Fruit follows the flowers in June and July. Though many will argue that the wild berry is superior in flavor to cultivars, many different species of low bush blueberry are available for purchase from nurseries. While this specific species may be difficult to find, hybrids abound and researchers have found some success breeding early fruiting varieties for commercial use.
Callaway Ginger Hexastylis shuttleworthii var. harperii
Hank Bruno, Trails Manager at Callaway Gardens tells us that “Callaway Ginger Hexastylis shuttleworthii var. harperii was brought to the gardens by Fred Galle, Director of Horticulture, in 1965. It was among plants rescued from the estate of plant collector J.G.C. Bloodworth in Decatur, GA when that property was subdivided and developed. There was no record of the original location of the parent plant. Recognized as different from the species, Galle propagated and shared it with gardeners and nurserymen. It became known as Callaway ginger and is now widely cultivated. In 1987 botanist L.L. Gaddy assigned the varietal name harperii to this distinctly mottled ginger in honor of its original discoverer Roland Harper.” Though identified as Hexastylis here, you will often find the plant identified as Asarum shuttleworthii callaway.
Though the species is common in the mountains of the Carolinas and down through Georgia and Alabama, and forms an attractive evergreen groundcover, the harperii variety is rare in its range, and has suffered from habitat loss due to draining or filling of wetlands for development. The variety is shorter than other gingers – just three inches tall – which makes it easier to see the late spring flowers which are typically hidden under the leaves. These flowers are bell shaped with a purplish cast and appear in May. A relatively slow grower, it will take ten years to achieve a three foot wide patch, but the wait is worthwhile. The half dollar sized leaves with their dark green background and dramatic silver venation make a striking addition between rocks or among small ferns in a woodland garden. Hardy in zones 5-9, Callaway needs shade, good soil, and constant moisture. Too much sun may cause slight burning of the plant. Often found in acidic soils near Mountain Laurel, Rhododendrons and other acid loving plants, gingers are easy to identify by the strong ginger sent produced when the leaves are crushed. While the root can be used as a substitute for culinary ginger Zingiber officinale, the slow growing nature of the plant makes it impractical for this purpose.
Pink Lady’s Slipper Cypripedium acaule
The Pink Lady’s Slipper is a dramatic
native orchid also known as Moccasin Flower, and found in acid woods, often near pines. Preferring full shade to partial sun with moist soil, Theresa Schrum, Vice President of the Georgia Native Plant Society told me she “once had a soil sample tested from a lady slipper site and the pH came back at 4.5! That's pretty acidic and this site was full of lady slippers that were spreading until the bulldozers got them.”
This is the only Lady's Slipper with basal leaves only. The flowers are irregular in shape, and of course, they are pink. Blooms first appear in mid spring and continue into late spring. The 'moccasin' and 'slipper' in the common names reflect the Indian and white settlers view of what the flower looked like. The flower is cleft in the middle, and has the unmistakable slipper, or moccasin shape to it.
This cleft is actually an entrance for insects, which acts as a one-way door. Inside the flower, small hairs "direct" the insect (usually bees) where to go, and some never do make it out. If they do manage to follow the hairs properly they are sent through a very narrow passage, which forces the bee or whatever bug it may be to be coated in pollen.
Though sometimes hard to find, the Pink Lady’s Slipper is available from specialty mail-order sources or through authorized native plant rescue programs for use in the landscape. Here in Georgia where the plant is protected, we need a special permit to rescue the plants.
A good deal of debate has arisen around methods for digging this plant in rescue situations. According to our own David Mellard, PhD, “When rescuing C. acaule, the one thing you should do is leave your shovel at home. Like the spokes of a wheel, the roots of C. acaule grow horizontally in the decaying pine duff microclimate.” As for creating the proper environment to receive these plants, “probably the most important thing is plant the roots horizontally on the surface, covering with compost, and most importantly watering them with vinegar (2 oz/gallon) throughout the growing season.”
The Pink Lady’s Slipper can be found in the foothills and mountains of Alabama, Georgia, South Carolina, adjacent Tennessee, and North Carolina, north and west to Alberta. Though protected in many states, it appears secure in most of Canada. In 1991, the state of New Hampshire adopted this stunning orchid as the state wildflower, where it is quite populous. Though it is not protected there, a persistent myth that it is has most likely contributed to the security of the population.
Conclusion
I hope that something in one or more of these descriptions has sparked your interest to learn more about the acid loving plants of Georgia. Though none of these plants will be appropriate for all regions of North America, plant communities do not recognize the boundaries established by governments. And a plant native to the Southeastern portion of the United States is likely to be a better choice for your garden, and the environment, than an exotic import that may escape cultivation and become a pest. Encourage nurserymen to take a new look at some old friends.
Where do they grow in the wild?
The big challenge was to select plant material that visually supported the architecture of the house and made the transition to the woodland. A few fast growing tall trees were needed in addition to understory trees, and shrubs. Because we have very few native evergreens suited to this elevation, Cynthia selected natives from elsewhere in the Southeast that she felt could adapt and thrive. For example, Bald Cypress Taxodium distichum is a highly adaptable, fast growing tree reaching to 70 feet with a narrow pyramidal habit. Even without a lawn, areas for relaxing should be included. Think about how the scene will evolve as the landscape matures to ensure trees and shrubs won’t block the view.
