For Shady Sites-Grasses Or Ground Covers

Perhaps the knottiest problem the lawn-builder has to face is trying to make grass thrive where it just naturally does not want to thrive—in shade. The shaded lawn, if we are to judge by the high percentage of failure, has not yet benefited greatly from modern scientific advances in other phases of turf culture.

Shade is a variable quality. A solid wall or building may throw a shadow into which no sunshine penetrates at any time. If, however, overhead branches do not obscure the sky, the area may seem quite light and airy. This is not enough light to produce a fine turf.

Shade may vary greatly during the day, from hour to hour; an area may have full sun at one time and dense shade another. If the total sunshine is more than two hours during the day, grass will survive. Even filtered, shifting shade, such as comes through the foliage of elms that arch high, or sifts through the fine foliage of a honey locust, will allow grass to grow. The total sunlight falling in flashes through the leaves is enough for growth.

One point that must be checked carefully is the variation in shade from week to week, due to the shifting of the sun's position in the heavens with the change of seasons. It is well enough to check on June twenty-first and find the sunshine period is three hours long, but what will it be in mid-July? Always take the seasonal variation into account in deciding whether a given area is fit for a lawn.

Under the branches of trees (which is what most people mean by shade), three of the four vital elements of growth are wrong for grass. All plants need heat, light, moisture and food. We can dismiss heat as a problem: usually temperatures under trees are adequate for growth. What about the other three?

In The Right Light

Light is the one lack which is all but impossible to make up. Unless we are willing to trim trees high, or even cut them down, not much can be done about light.

As to food and water, deep-rooted trees, such as planes and oaks, are not as greedy as those with shallower root systems such as the white ash and the maple. Nonetheless, any tree removes vast amounts of water from the soil—easily a barrel or two a day for a mature specimen. Since this moisture is removed from below, it is not available to rise to the surface by normal soil capillary action. We can readily see, therefore, that moisture will always be scarce under trees. Even when liberal amounts of fertilizer are used, this does not always make up for a lack of plant food in areas under deep-rooted trees because lack of moisture keeps it from being available. Also, bacterial action is slowed up, and humus is not formed from an overlying layer of leaves. Under shallow-rooted trees, this situation is made even worse by the fact that the trees themselves absorb the available nutrients faster than the grass.

With food, light and moisture all critical factors, the growing of grass under trees is a really knotty problem to solve. Unless water can be supplied (at least enough to keep the grass going through the driest periods), a turf cannot be maintained. Disjointed plants are possible, but they do not run together and form a real sod. The new ureaform fertilizers are excellent if moisture can be supplied, but if the soil is dry, bacteria cannot break them down, and they fail to feed. For this reason, perhaps the best way to feed a shaded lawn is with liquid fertilizers watered through a hose with a siphon device which sucks up a concentrated solution and adds this to the water in the line.

Best Shade Species

The best grasses for shade are Pennlawn Fescue, with Penn State or Illahee Fescues as second choice, and perhaps with a little Merion on the chance that the shade is not so dense that this will fail. Poa trivialis should be included in a shade mixture only if the spot to be seeded is low, moist and rich. I know this is contrary to all recommendations in the literature on lawns, but anyone who has grown Poa trivialis experimentally under controlled conditions knows that it has high moisture and food requirements, which cannot be met under ordinary shade conditions.

If only Velvet Bent were not so costly! This is a grass well adapted to shade, and while it can use more food and water than the fescues, it can also survive without these extras and will do very well. Its color and texture are superior to the fescues.

Where the amount of sunshine will total three hours a day, I strongly urge a trial of Merion Kentucky Bluegrass. This grass will tolerate more shade than is commonly realized. Its one drawback as a shade grass is that, to thrive, it must be well fed. It can get along with less moisture than most grasses.

The soil under trees can be improved, but beware of peat moss under such conditions unless artificial watering is used. Peat moss is very hygroscopic, and will draw moisture to itself at the expense of the surrounding soil. Peat moss can absorb so much water that the rest of the soil mass mixed with it will dry out. Other organic matter is helpful in retaining moisture, but, as always, the problem of keeping it moist must be faced in shade under trees.

Ground Covers

For some reason, some American gardeners look upon ground covers as a sneaking subterfuge to get away from caring for a lawn. They seem to feel it isn't quite cricket to quit trying to grow grass where grass won't grow. In my town there is even an ordinance which prohibits the planting of anything other than grass on parkways. This was probably intended to stop the planting of tall shrubs and sight-obscuring hedges, but has been interpreted so as to prohibit even a ground-hugging euonymus from "profaning" this strip of earth.

As a result, many town streets are lined with mile after mile of turf in poor condition, with decent grass to be seen only in new sections without trees, or where Dutch elm disease has killed out a few sun-stealing street trees.

This reluctant attitude toward ground covers is at odds with the facts. A well-groomed planting of low ground covers is often more interesting than the most perfect lawn, and usually attracts more attention. I know this from personal observation.

Between my sidewalk and house is as fine a stretch of four-year-old Merion lawn as can be found anywhere. On the south side of the drive a giant white ash shades an area so thoroughly that, in theory, grass should not be able to grow. The area never receives direct sunshine; it gets only the little that trickles through the foliage of the tree. In spite of the lack of ample sunlight, and in spite of the high rate of consumption of food and water by hungry tree roots, I have managed to establish, at a heavy expenditure of time, labor and water, a perfect stretch of Penn State Fescue. But just behind this is a planting of a unique ground cover for our part of the United States—a bank of the hardy Baltic variety of English ivy. While my Baltic Ivy is especially lush and dark green, the fescue lawn is a real tour de force which would be noteworthy anywhere. In spite of its rarity in such a location, I have never had one person comment on its perfect texture and rich color. Yet everyone exclaims over the Baltic Ivy ground cover as though it were a gem of rarest cut.

When you consider that my home has been visited by the editors of practically every important garden magazine in the country, and that trained horticulturists from the United States and Europe have commented on this ivy planting, obviously a ground cover is valued as something more than a second-rate substitute for a lawn. Indeed, it is a superior way to develop shaded areas, and one that beautifully solves some very difficult problems.

List Of Good Ones

Most of our troubles with shaded areas would vanish if we would consider ground covers not as a substitute for turf but as improvements on the best grass one can grow under trees. Nor need we confine our thoughts to shade: most of these plants are equally valuable for that sloping area where a terrace would be out of place or too costly to construct. Soil too rocky or shallow for grass would be lovely with a cover of wild thyme, fragrant in the sun. The possibilities are endless, limited only by the imagination of the gardener. Here are a few suggestions (including some for sunny spots also):

Basket of Gold, Gold Tuft (Alyssum saxatile compactum): A blaze of golden yellow for a short time in spring, this perennial— the rest of the year—offers good but uninteresting foliage for sunny slopes.

Bearberry (Arctostapkylos uva-ursi): One of the few ground covers that will grow on practically pure sand. Requires acid soil. Accepts sun or shade. It has small, thick green leaves.

Carpet Bugle (Ajuga reptans): A wonderful ground cover in shade, with clear blue flowers on short stems; dark green oval leaves. The variety, atropurpurea, is a maroon-to-purple-leaved plant that forms gorgeous mats of color in light shade. At the Stribling Arboretum in Golden Gate Park, San Francisco, this bugle beats many rare plants for the attention it attracts. There is a variegated variety of Ajuga reptans—bronze, yellow and green—that is striking: it should be wonderful when available at a lower price so it can be used as a mass ground cover.

Creeping St. John's-wort (Hypericum repens): A 3-inch-tall gem with golden flowers. Marvelous in full sun.

English Ivy (Hedera helix): If this can be kept out of the winter sun, it is magnificent. The variety Baltica, Baltic Ivy is as hardy as a white oak. Both are easily propagated by cuttings.

Geneva Bugle (Adjuga genevensis): The true species of this is too vigorous and tall (about 14 inches) for most places. It needs some moisture, but grows well in shade. (See Carpet Bugle.)

Goutweed or Miterwort {Aegopodium podograria): This gets a little weedy at times but can be kept down if you mow it with a sickle once or twice a year. Both green-leaved and variegated varieties are available. It grows in dry soil in sun or shade.

Japanese Spurge (Pachysandra terminalis): To many people this is the ground cover. It is certainly vigorous and shade tolerant. I find its olive-green leaves a drawback, but if that color suits you, there is nothing better.

Lily-of-the-Valley (Convallaria majalis): This ground cover is almost indestructible. While it will flower better if given extra moisture, it tolerates drought to an amazing degree. If it were not so common, it would be more highly prized.

Max Graf Rose (Rosa rugosa variety): A creeping Rugosa Rose that forms sturdy mats of flower-laden stems in full sun. One landscape architect specified half a million plants of this rose on a highway job: the order was never filled because there weren't that many plants to be had. There should be enough available for your sunny slope, however.

Moneywort (Lysimachia nummularia): Does well in sun or shade, but requires moisture. Bright yellow flowers. Makes a solid cover under good conditions.

Periwinkle (Vinca minor): I use this common name rather than its other cognomen, grave myrtle, which does not do it justice. It is one of the best of all ground covers for shade, with bright, clean foliage and blue flowers. Bowles variety flowers more freely, with larger individual blooms.

Poscharsky Bell flower (Campanula poscharskyana): Why a plant as fine as this should have to bear a name as ugly as this is difficult to say. It is a gem: perfect billows of lovely blue flowers on 4-inch plants in full sun. Blooms from June to frost.

Prostrate Junipers (Juniperus species): Every nurseryman can supply at least two or three forms of creeping junipers; they are among the finest of all ground covers for full sun or light shade.

Ratstripper or Canby Pachistima (Pachistima canbyi): If this had a decent common name, it would surely be a commonly used ground cover, for it is like a tiny holly plant with 1-inch leaves that turn lovely bron2y green in fall. Needs some shade and an acid soil. Grows to about 10 inches, spreading by underground shoots.

Sedum Species: Most of the creeping forms of Sedum can be used as ground covers but they must have sun. Some are quite invasive.

Strawberries (Fragraria species): The woods strawberries are excellent in light shade. For a real treat, get seed of the variety Baron Solemacher, the true Alpine berry, which will grow and fruit in shade. Delectable fruit.

Sweet Alyssum (Alyssum maritima): This annual is cited only because it can often solve the problem of the sunny site that needs something which stays low and has good flowers. The low plants are covered with fragrant white compound heads of bloom.

Winter Creeper (Euonymus radicans): It is perhaps the most useful of all evergreen ground covers. The variety Colorata has leaves with beautiful maroon-colored backs. The variety Minimus is also a beauty that grows very slowly and should not be expected to cover large areas.

Home Propagation

One drawback to a wider use of ground covers is their cost per square foot. But, with a little care to details, a plant or two can be purchased and propagated by cuttings or divisions. A bed of sand or vermiculite, protected from direct sun by lath or burlap shade, will enable the home gardener to make at least 100 new ivy plants in a year from one original pot plant. Some plants, like lily-of-the-valley, can be increased by simply dividing the clumps.

Feeding Ground Covers

All of these ground covers except Bearberry will grow better if given some good mixed fertilizer once a year, preferably in spring before growth starts. Feeding may cause some species to grow taller than wanted, in which case simply reduce fertilizing. Shade-tolerant plants are tougher than they look, and will survive on a semi-starvation diet.

Chips Off The Chapter

1. Shade can be the homeowner's friend or enemy, depending on how he reacts to it in the landscape. Shade can be cast by buildings and by trees; the latter is the more difficult because trees also rob the soil of moisture and nutrients.
2. Certain grasses grow well in shade; proper selection and maintenance are essential.
3. In many cases the most practical and decorative solution for shaded sites will be found among the numerous creeping or low-growing hardy plants that are roughly lumped under the heading, ground covers. Some of these plants have evergreen foliage, and quite a few provide highly ornamental flowers in season.

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