Nature’s Curse

A dry shade garden. What could be worse? No sun. No moisture. You can’t have a cut flower garden, nor a woodland garden. The one wants sun, the other moisture. So is there hope for the gardener cursed with dry shade? Fortunately, the answer is a resounding yes, and this discussion will focus on those shrubs and perennials that actually thrive in dry shade. But it must be stressed that even these tough plants need regular water until they get established.

Although Ash Wednesday marks the beginning of Lent, a period of sadness for Christians, it also signals one of nature’s most welcome events, the flowering of the Lenten Rose or Helleborus (hardy in USDA Zones 6-9). Rising from clumps of evergreen leaves, these blossoms come in a rainbow of colors, a palette that is rapidly expanding as hybridizers rush to satisfy a surging demand. Hellebores owe their popularity not only to their early display, but also to their love of shade and dry soil. Once they have settled in they will self sow, or for more control increase your stock by dividing older plants in late fall or winter. And for those gardeners battling browsing deer, take heart; hellebores contain poisonous alkaloids, a highly effective deer deterrent.

A couple of months after the hellebores have bloomed, the vivid pink and purple flowers of Geranium macrorrhizum emerge, brightening a shady spot or lighting up the shadow cast by a rock wall. Commonly known as Bigroot Geranium for its thick rhizomes that spread vigorously, this sturdy groundcover can tolerate the hot humid summers of the South (hardy in USDA Zones 3-8); their fat roots store enough water to keep the plant vibrant. The flowers, beloved by butterflies, fade in late spring, and that’s the time to give your geranium a haircut. As the summer days grow shorter, the geranium’s spicy scented leaves turn multiple shades of orange and red and lasting well into winter.

Blooming at about the same time another dry shade lover, Bergenia cordifolia also spreads by rhizomes although at a much slower rate than the geranium.
A handsome groundcover, Pig Squeak, so dubbed by the sound made when two leaves are rubbed together, sports tiny showy pink flowers in spring standing tall above glossy green leathery leaves that turn purplish bronze in the fall (USDA Zones 3-8).

Often mistaken for orchids the dainty nodding flowers of Epimediums, the final flowering perennial group chosen for a dry shady area, actually belong to the Barberry family.
Flowering in early spring epimedium blossoms span a vast spectrum of colors including all shades of pink and purple, yellow, orange, red or white, and the leaves are just as varied, purple, green, bronze; only your taste limits your choice. Hardy in USDA Zones 5-9 these Asian natives may be grown as groundcovers or as specimen plants, they may be deciduous or evergreen; again the choice is yours. For more information on this remarkable genus see the blog post These Leaves Shine in the Shade.

For a more casual look consider planting the weeping willow of grasses, Carex, a grass look-alike that actually is a sedge.
With over 1500 species in the family the gardener can choose a blue carex, or a green one with ivory stripes, solid green, or green with white margins – the choice is almost limitless. And the uses of this elegant plant are equally varied; plant it to soften a wall, serve as a point of focus, or control soil erosion on a dry shady slope. Holding its color through winter in the warmer climes (it is hardy from USDA Zones 5-9) its strappy leaves turn bronze the farther north you garden. But no matter how it ages through the seasons, the interesting texture of a carex always enlivens a winter garden.

Lovers of dry shade are not limited to perennials; many shrubs prefer those conditions as well, and Kerria japonica is one of the most colorful.
Bursting with vibrant yellow blossoms in early spring long before its puckered green leaves emerge, this graceful specimen is named for an 18th century head gardener at Kew Gardens. A mature Kerria can grow to be 6 feet by 6 feet, but if that size threatens to eat up your garden, whack it back to the desired size right after flowering. Even in winter this beauty continues to delight the eye; bare of leaves its vivid green branches stand out, especially in a garden smothered in snow (hardy in USDA Zones 4-9).

Another colorful shrub that flourishes in dry shade is the Missouri native Physocarpus or Nine Bark, named for its exfoliating bark that peels away in strips.

Blooming in May a little later than the Kerria the pinkish white clusters of flowers are a knockout against the purple leaves of the cultivar ‘Diablo’. For a brighter variety chose ‘Amber Jubilee’ whose orange, yellow and gold leaves will cheer up any dreary spot. Hardy from USDA Zones 3-7 the deciduous Nine Bark tops out at about 6 feet, but if you want to contain it prune it after it has flowered.

No discussion of shrubs that flourish in dry shade would be complete without mentioning the Boxwood family. Everyone knows English boxwood; it’s the most popular landscape shrub in the country, but it does have its drawbacks, slow growth rate and foul odor among them, so this discussion will focus on its lesser known cousin, Buxus microphylla var. sinica or Korean Boxwood.
Not as formal as English boxwood, it is evergreen (USDA Zones 4-9), a big selling point, although in the colder climates it tends to turn bronze and should be protected from winter winds. Search for the cultivar ‘Wintergreen’ if you want a tough shrub that holds on to its green color through the winter. At maturity a Korean boxwood will not get much taller than 4 feet, and although it blooms, the highly scented flowers are sparse and insignificant.

If it’s fragrance you’re after one of the most outstanding choices is Sweet Box or Sarcococca ruscifolia (USDA Zones 7-9). In late winter tiny white flowers peek out from glossy green leaves and fill the air with a sweet vanilla scent, and after the flowers have died bright red berries take their place. Plant this shrub where both the fragrance and the winter display will be fully appreciated, by an entrance door or flanking a walkway. Be sure to give enough space for your Sweet Box; when it is fully grown it will be about 3 feet wide by 5 feet tall. If you absolutely have no room for another shrub no matter how outstanding consider planting the groundcover variety S. hookeriana var. humilis.
A native of the Himalayas this variety of sarcococca grows only 1 to 2 feet tall and differs from its taller brethren only in berry color; it produces black fruit rather than red.

The final shrub selection for a shady dry area is Nandina domestica, Heavenly Bamboo, so named because it was often cultivated by monks in their temple gardens.
Grown in USDA Zones 6-9 it is evergreen in all but the coldest climates, but even there it will drop only a few leaves in winter. Come spring the lacy green foliage breaks out followed by bunches of tiny white flowers, but many gardeners prize it most for its fall color, a rich deep burgundy, and its clusters of drooping red berries. For the best fall color, try to give it some sun and for the best berry show plant several nandinas together. However, if you garden in the southeast and are concerned about its invasive habit select one of the cultivars that produces little or no fruit; ‘Fire Power’ and ‘Gulf Stream’ are two good selections. The foliage of ‘Fire Power’ emerges a bright lime green in spring and turns fire engine red in the fall. ‘Gulf Stream’, one of the bushiest and most compact of the nandinas, sports bronze leaves with orange tints throughout the growing season.

So as this discussion illustrates, by choosing plants wisely and watering them well early on a gardener can break nature’s curse and bring life and light to the most inhospitable of sites, a dry and shady garden.

Shrub and Perennial Plant Resources

Bluestone Perennials
www.bluestoneperennials.com

Nature Hills
www.naturehills.com

Lazy S’S Farm
www.lazyssfarm.com

Monrovia
www.monrovia.com

Photo Credits

1. Hellebores – CC BY-SA 3.0
2. Geranium macrorrhizum – Hardyplants
3. Bergenia cordifolia – Christain Hummert
4. Epimedium – Peter Coxhead
5. Carex halleriana – CC BY-SA 3.0
6. Kerria japonica – Jeffdelonge
7. Physocarpus – Jean-Pol GRANDMONT
8. Buxus microphylla var. sinica – Sten Porse
9 Sarcococca hookeriana var. humilis – CC BY-SA 3.0
10. Nandina domestica – Public Domain

Nasty Plants

Most gardeners have heard the story of the evil kudzu, the “Vine that Ate the South”. Originally introduced as an ornamental plant at the Philadelphia Continental Exposition in 1876 it remained benign until the mid 1930’s when it was planted extensively by mid-western farmers to control soil erosion caused by dust storms. Soon kudzu turned into a plague rather than a cure, swallowing up native plants, abandoned houses, broken down cars, telephone poles, in short, anything standing still. Most invasive plants are not quite as aggressive, and some can even serve useful purposes, but it pays to know which plants are likely to give a gardener a bad rep and a hard time. Here are a few of the worst culprits.

One of the top offenders is Euonymus alatus, Winged Euonymus or Burning Bush whose invading range extends from New England through the mid-west.

Brought into the United States in 1860 as a decorative shrub and prized for its brilliant fall foliage and corky stems, the fruit is much beloved by birds who then distribute the seeds far and wide. Once Burning Bush gets established it snuffs out all native plants in the vicinity so just be aware that if you decide to plant a Burning Bush, your neighbors a couple of miles away might be less than thrilled with your decision.

1860 also saw the introduction into the US of another ornamental shrub, Japanese Barberry, Berberus thunbergii (what were the Victorians thinking?).
Highly valued as a hedge it is easily shaped, has rich winter color, produces vibrant red berries and is deer resistant (deer have no taste for the thorns). As with Burning Bush birds disseminate the seeds of the red berries, and once they take root in woods and meadows they grow rapidly, forming dense thickets and smothering native plants. As if that was not curse enough, barberries harbor swarms of black-legged ticks, carriers of Lyme disease among other scourges. Difficult to eradicate with no known predators, the only way to control the spread of barberry is to dig it, burn it or zap it with Roundup. Because of its invasive habit many states have banned the sale or trade of Japanese Barberry.

Then there is a whole family of aggressive invaders, the Bamboos of which Phyllostachy aurea or Golden Bamboo is the black sheep.

A fast growing screening plant that quickly produces an impenetrable forest of slender stalks, bamboo falls into two categories – it can be either clumping or running. Although few nurseries sell the running variety because it literally runs amok, even clumping bamboo requires restraint, demanding either annual root pruning or enclosing the roots with a 30inch deep plastic barrier. Yet taking these precautions does not guarantee that it will behave – bamboo has been known to spring up 50 feet away from the mother plant and even jump driveways. Astonishingly one homeowner reported that bamboo shoots sprouted through his basement floor, not a dirt floor, a cement floor. The only sure fire way to keep it under control is to plant it in a container and treat it as a handsome specimen.

Invasive plants are not just limited to woody shrubs; some flowering perennials have made the hit list as well. The top contender for Evil Perennial of the Century is Purple Loosestrife or Lythrum salicaria, a stately plant with magenta flowers that often is spotted in wide swathes along the nation’s highways causing the occupants of passing cars to ooh and ah.
Perhaps they would hold their applause if they realized they were celebrating a plant that the World Conservation Union has labeled one of the world’s 100 worst invasive species. Yet despite condemnation by guardians of the environment, Purple Loosestrife still is widely available commercially; only a few states have banned its sale. Thought to have been brought to this country in a ship’s ballast, this self-sowing devil thrives in sunny wetlands, and its only known predator is a European beetle that feeds exclusively on the leaves. In an attempt to control the spread of Purple Loosestrife, many states have instituted programs to release these beetles into the wild, programs that have proved fairly successful thus far.

Another invasive species often sighted and sited beside roadways is the charming Ox-eye Daisy, Leucanthemum vulgare, whose bright white petals and golden yellow centers liven up long stretches of highway.

Often confused with its taller sister, Shasta Daisy (Leucanthemum x superbum) which is not invasive, the Ox-eye daisy can produce up to 26,000 seeds per plant, seeds so sturdy that even when buried they may remain viable for more than 25 years. Resistant to many herbicides, the most effective control is to dig the plant and destroy it, and for those gardeners thinking of planting a wildflower mixture, check the contents of the seed packet; often Ox-eye Daisy seeds are included.

An aggressive groundcover, Creeping Jenny or Moneywort thrives in sunny moist locations. Named for a Macedonian king Lysimachia nummularia spreads rapidly, its brutish behavior snuffing out lesser plants in its path. In spite of its reputation as a brute, Creeping Jenny serves as a colorful groundcover with its bright yellow flowers and penny-shaped chartreuse leaves; just be sure to keep an eye on it lest it breach its boundaries.

In spite of its popularity and widespread availability, the groundcover Vinca minor, or Myrtle is on many states’ list of nasty plants.

Introduced in the 1700’s for its medicinal properties, it quickly gained widespread adoption as an ornamental low growing plant – evergreen, easy to grow even in deep shade, and best of all, producing delicate blue flowers in early spring. An ideal groundcover one would think except for one drawback; it roots from the tips of runners forming a dense mat that smothers any plant in its way. Caution is advised when planting a vinca minor bed; it may branch out, spreading its long arms into unwanted places, the middle of your lawn, for instance. Since its waxy leaves repel most herbicides the only sure fire way to eradicate errant plants is to pull them up.

In addition to woody shrubs and perennial plants, two aggressive vines are renown for taking over their neighborhoods. The first, Lonicera maackii, Amur Honeysuckle was initially valued for its fragrant creamy white flowers, black berries and rapid growth,
but later reviled for its invading and marauding habit; many states have banned the sale and distribution of this honeysuckle. Brought to this country in the mid 19th century as an ornamental plant it turned out to be just as nasty as Japanese Barberry and Burning Bush two plants that arrived on these shores at about the same time. As is the case with many invasive plants, birds feasting on the berries can be blamed for the spread of honeysuckles, and with no known natural predators the only control methods are digging, burning or spraying with a glyphosate such as Roundup.

The final nasty plant selection Hedera Helix or English Ivy has been in this country since colonial days brought by the early settlers to add a touch of home to their gardens.
Growing in partial to full shade it makes an ideal woodland groundcover, but it also can morph into a vine, scrambling up tree trunks, blocking the sun and causing the decline and death of its host. In spite of its thuggish behavior many have been awed by the beauty of ivy-covered facades of many buildings on old college campuses (it is reputed that’s how the Ivy League schools got the moniker), but beauty is in the eye of the beholder; just ask any owner of a brick house who has footed the repair bill for the havoc wrecked by the tenacious tendrils of English Ivy.

This discussion only touched on the worst of the invasive plants; the list is extensive with new varieties added yearly – similar to the endangered species list, they both are expanding but one is threatened and the other is threatening. Just as gardeners check the sun and soil requirements before planting any new specimen, so too should they check the growth habit in case they inadvertently create a monster.

For More Information:

www.invasivespeciesinfo.gov

www.invasive.org

www.invasiveplantatlas.org

Photo Credits:

Euonymus alatus – Chris Borton CC BY-SA 3.0
Berberis thunbergii – Sage Ross
Phyllostachys aurea – Kurt Stuber
Lythrum salicaria – Saffron Blaze CC BY-SA 3.0
Leucanthemum vulgare – Derek Ramsey
Lysimachia nummularia – CC BY-SA 3.0
Vinca minor – Ryan Kaldori
Lonicera maackii – Wouter Hagens
Hedera helix – H. Zell