Gardening in the Shade
by Tony Avent
Written for The News and Observer, Raleigh NC, May 24, 1997
Shop for shade garden perennials at Plant Delights Nursery
Although I grew up in wooded areas most of my life (not abandoned or anything like those tarzan stories), I have always taken gardening in the shade for granted. My first effort at being a garden owner was in a sunny garden, as was my second. Only after clearing away the dense undergrowth from a lowland area in my second garden did I again have the chance to garden in the shade.
The more of my woodland garden that I cleared, the more time I spent in that area, even to the point of neglecting some of my more sunnier garden spots. It is as though something magical keeps drawing me back to that area. It's been interesting to watch tour groups traverse our garden, and almost subconsciously like the swallows to Capistrano, they immediately migrate through the sunnier parts of the garden to the shady areas.
There are as many theories to explain our love of shade garden as there are people to espouse the theories. Perhaps it is our longing for enclosure that is satisfied with the canopy of a tree, or perhaps it is simply the search for a cooler spot on a hot summer day. Ironically, visitors from countries like England always migrate to the sunnier beds...perhaps tired of their overcast perpetually misty climate. I am always amazed how few shady gardens there are in England.
When we talk about shade, we all have our own ideas about what is shade. I like to begin by explaining that all shade is not created equal. It's sort of like going to the store and asking for white paint. A clerk will quickly respond, "Do you want flat white, glossy white, antique white, eggshell white, clear white, or what?" You see, all shade is not necessarily the same.
I like to define shade by using several categories: morning shade, afternoon shade, light shade, and dense shade. Dense shade is by far the most difficult type of shade in which to garden. If you go out into a stand of old woods, especially old oaks and maples, you are probably experiencing dense shade. By the lack of substantial vegetation on the woodland floor, you can quickly surmise that little grows in dense shade. The problem is that plants need light to photosynthesize and produce food, so only those plants with low metabolism are able to survive.
Light or partial shade is an ideal condition to grow a wide variety of wonderful garden plants. Light shade occurs where there are smattering of large and small trees, where indirect rays of light can filter through the canopy of limbs. This can be artificially accomplished by selective removal of trees in a forested areas, and through removal of many of the lower tree limbs.
Morning and evening shade areas of your garden are those that receive shade during most of the day, but get a few hours of direct sun, either in the morning or evening. This area is reserved for plants that can take direct sun, but don't like our summer heat. Generally, plants that prefer cooler conditions benefit from sun in the morning and afternoon shade during the heat of the day, while plants that love heat benefit from shade in the morning and prefer to bask in the hot afternoon sun.
Other than the age old issue of soil preparation and enough irrigation to account for the tree roots, the recipe for successful shade gardening lies in the correct plant selection.
Plants fail to fall into neat groups, but lets begin with a few choices that would be great for ground covers in the woodland area. There are a variety of choices including acorus, astilbe, asarum, ajuga, antennaria, lysimachia, microbiota, ophiopogon, phlox, saxifraga, and a host of others.
The group of grass like acorus (Acorus gramineus) are 6" tall or less and slowly spreading ground covers that prefer moist sites, even standing water. The evergreen foliage in green, gold, or variegated are the main feature. In the astilbe group, there is only one species that is well adapted to our heat, and that is A. chinensis. A dwarf spreading form Astilbe chinensis pumila is a fabulous ground cover plant for dry shade with its pinkish purple bottle brush like plumes in July. While most astilbes must have lots of moisture to survive in the south, this is the one notable exception.
One of our most popular natives that deserves wider use is our native wild gingers. The hexastylis (recently renamed asarums) have mostly evergreen heart shaped leaves that form attractive clumps often with silver mottled leaves. There is one notable spreader that makes a great groundcover, asarum shuttleworthii Calloway. The quarter size silver and dark green marbled leaves soon make a year round attractive mat in even dense shade.
Ajugas are certainly popular, as they have been for many years. Folks now are opting for many of the more colorful leaf forms, including A. Burgundy Glow and A. Pink Silver (Pink, White, and Purple foliage), A. Silver Beauty (white and grey green foliage), A. Grey Lady (Grey green foliage), and a host of purple foliaged cultivars. Ajuga will thrive in all except the densest shade, but during periods of extended rain like we have experience this summer, may die out in poorly drained soils.
One of my favorite ground covers is the hairy silver grey leaf pussy toes, especially our native Antennaria plantaginea. You will often see this durable ground cover on sunny road cuts, where nothing else will grow. You can also find pussy toes hiding in dense shade underneath giant oaks in the driest of shade. Other available pussy toes include the challenging to grow A. dioica, and the cute A. neglecta from the western US.
A longtime favorite is the wonderful native green and gold. When I once showed this to a friend who was mowing it in his Cary lawn, he was unimpressed. It was only after he transplanted some into the garden that the green felty leaves and bright golden yellow flowers began to show its their true splendor. While most green and gold (Chrysogonum virginianum) is a slow spreader, a new introduction, C. Eco Lacquered Spider has runners so long (to 3'), it could make a wandering jew blush.
A commonly grown groundcover are the group of moneyworts. Lysimachia nummularia if the most common with its rapidly spreading, but easy to remove dime size round leaves holding tight to the ground. I like the golden leaf form, L. nummularia aurea, although the leaves turn green in too much shade. Another choice member of the moneywort family is L. japonica minutissima. This tiny leaf green mound is covered with equally as tiny yellow flowers in spring. This can be used as a moss substitute for those that have trouble establishing moss. All lysimachias prefer slightly moist soils.
I think most folks have tried to plant junipers in the shade, and although the plants take a while to die, there looks are far from appealing. Enter the siberian false juniper, Microbiota decussata. This juniper look alike from Siberia prefers light shade in our area. Just like a ground cover juniper, it can easily spread to 4+ feet in width.
Another favorite ground cover for woodland garden, from the deepest shade to the edges of the sunny garden are the mondo grasses or ophiopogons. These tough as nails evergreen ground covers now come in a variety of colors and sizes from black leaves, O. planiscapus Arabicus to dwarf O. japonicus Gyoku Ryu, to a nearly a dozen variegated cultivars. Although slow to initially spread, given about three years, they make a mat impenetrable to all but the most invasive of weeds.
Another favorite of mine is our native woodland phlox, P. divaricata (aka Wild Phlox). In the spring, the evergreen ground hugging mat is topped with 12" spikes of intensely fragrant blue flowers. I like to interplant this ground cover with other plants of interest during the summer season.
There are a couple of commonly grown greenhouse hanging basket plants that also make great woodland ground covers, strawberry begonia (Saxifraga stolonifera) and piggyback plant (Tolmiea menziesii). Both of these hardy groundcovers can tolerate dense shade and make nice mats of interesting foliage. The strawberry begonia also comes in a maroon foliage and green foliage forms.
One of the most under used and unique shade loving ground covers are the group of selaginellas. They are close relatives of another well know Christmas decoration, running cedar (Lycopodium sp.). The flat blue green foliage of S. uncinata (Peacock Moss) is one of my favorites, along with the upright foliage of S. involvens. Both selaginellas prefer moist shade.
There are a variety of shade loving plants that make great accent plants or specimens in the garden. One of the best known is the group of hellebores. These European natives for large evergreen clumps to 1-2' tall x 1-2' wide. The most popular is the lenten rose (H. hybridus or H. orientalis). These reseeding clumpers offer a dazzling array of winter flowers in colors of pink, white, yellow, red, and purple. H. foetidus, unlike the lenten rose grows its green finger like foliage on a 2' stalk. The green bell like flowers, borne by the hundreds adorn the plant during the dead of winter. The other popular hellebore is the Christmas Rose, with it's late winter 1-2" flowers of clear white.
Another plant that has enjoyed a recent resurgence is the coral bells (heuchera). Thanks to the incorporation of our native H. americana into the west coast breeding programs, we can now color up our light shade gardens with wonderful foliage such as Heuchera Chocolate Ruffles, Ruby Ruffles, Velvet Knight, and Persian Carpet. Heucheras are short lived plants and do best if divided every 2-3 years.
Where would we be without another woodland great, the bleeding hearts. Most folks grow one of two bleeding hearts, the spring bloomer with the 3' arching spikes of pink heart shaped flowers that goes summer dormant (Dicentra spectabilis), or the spring and summer blooming types (D. formosa and D. exima) that rest their sprays of pink flowers on very cutleaf ferny foliage.
A close relative to the bleeding hearts are corydalis...pronounced cO-rid'-ilis. The foliage appears quite similar, although the flowers are in entirely different color including white, tan, yellow, and blue. Many of the corydalis are spring bloomers including C. lutea (yellow) and C. Blue Panda (blue). Others such as C. ochroleuca bloom during the summer (white).
A couple of woodland plants that everyone tries to grow, but usually fail are bergenias and ligularias. The problem is our summer heat that often make molten piles of foliage from many northern favorites. The trick is to find the right species or varieties for our area. For bergenias, the only species that is reliable in our area is B.ciliata (hairy bergenia). For ligularias, the only sure success in our climate is Ligularia tussilaginea. L. tussilaginea comes in solid green leaves, yellow spotted leaves, and a crested green leaf.
I guess the plant that takes the most shade is a Japanese plant called rohdea or sacred lily. In Japan, rohdeas are collectors plants, with each different variation increasing the value of the plant, often into the thousands of dollars each. All of the rohdeas available in this country are the solid green leaf R. japonica. Rohdeas have been often described as an evergreen hosta.
For a taller plant for the woodland, don't forget the group of solomon's seal that include the genera of polygonatum, disporum, and smilacina. These arching perennials have predominately white bell shaped flowers in early spring.
You have no doubt noticed that most of the woodland perennials flower in the spring. This is an evolutionary adaptation that was derived by the lack of leaves on deciduous trees in the spring. Plants that grew underneath the large deciduous trees found that they had to grow and flower while the leaves were absent and light was abundant. Once the trees leaf out and the amount of light diminishes, about all you will get is foliage.
There is one exception, and that is our native black eyed susans. Both Rudbeckia fulgida sulivantii Goldsturm and R. triloba flower prolifically in light shade. These are wonderful plants to help give color in the summer shade garden.
If you desire more of a tropical feel, then a couple of shade dwellers may help your garden achieve that Florida look. Both the needle palm (Raphidiophyllum hystirix) and the scrub palm (Sabal minor) would perform well in local woodlands. Also, a deep south favorite, the cast iron plant (Aspidistra elatior) is a southern specialty for very deeply shaded gardens.
Other woodland favorites include goatsbeard (Aruncus dioicus), columbines (Aquilegia sp.), sweet woodruff (Asperula odorata), hardy orchids (Bletilla striata and Calanthe sp.), northern sea oats (Chasmanthium latifolium), robbs spurge (Euphorbia robbiae), wintergreen (Gaultheria procumbens), dead nettle (Lamium maculatum), (both the native and asian mayapple (Podophyllum peltatum and emodi), lungworts (Pulmonaria sp.), foam flower (Tiarella cordifolia), spiderworts (Tradescantia sp.), toad lilies (Tricyrtis sp.), and of course hosta.
You have probably been wondering how I could omit hostas in an article about shade gardening, but that's only because they have their own article.