How many suburban places could have their general appearance improved if the masonry walls flanking the driveway or turn-around, or the walls enclosing the terrace, were converted into wall gardens?
How many hours of strenuous pushing a lawn mower up and down steep slopes could be saved? Were the lawn graded into several levels separated by planted retaining walls?
Such walls are just as helpful and so much more attractive.
As in every form of gardening, there is a right and wrong way to build a walled garden. However, it does take more thought, time, and labor than “to pile stones together.”
The latter haphazard method may suffice to mark the boundary of pasture land, but it needs to furnish better growing conditions for plants.
Here in the eastern states and in other sections where the problem of alternate freezing and thawing exists, it is well to make a solid base — by excavating 2’ feet deep and 2 ½’ to 3’ feet wide along the length of the proposed wall.
Broken pieces of rock, small stones, coarse gravel, and soil fill the excavation to ground level. The earth should be firmly packed — playing the hose on it will force it down among the rocks where it belongs.
The first layer of rocks is placed on this foundation and should reach back into the bank. Next, the soil is pressed in and around the stones to fill all spaces. This is important throughout the wall building, for air pockets mean death to plants.
Setting Up The Rocks
In setting the rocks, be sure they tilt downward at the rear to direct the moisture to the back of the wall, where most of the roots will be located. Also, as the wall gains in height, the face recedes approximately 1” inch to every foot.
Assuming the wall is 4’ feet high, the top row will be 4” inches back from the front of the base. This backward slope is to catch the rainfall needed by the plants.
Most of the plants adapt themselves to wall gardening, like neutral soil. A satisfactory composition consists of one part good loamy soil, one part sand, one part leaf mold, and one part well-rotted cow manure.
And I mean well-rotted; otherwise, air pockets may be created in the rock crevices as it ages and loses bulk.
Some plants, for example, Dianthus, Sedums, and Sempervivums, like leaner, grittier soil so that crevices accommodating them can be filled accordingly.
Other plants may indicate a preference for acidity, and their taste may be gratified by adding acid peat moss or oak leaf mold.
Planting In The First Layer Of Rock
Planting begins with the first layer of “rocks’ covered with about 2” inches of the soil mixture.
The roots, spread out carefully to their fullest extent in a little hollow made by scooping out some of the soil, are then covered with dirt and patted firmly.
The plant’s crown is level with the face of the rock below it, with the roots running to the back of the wall.
The planting continues in this manner until the length of the wall has been completed. Then the second row of rocks is laid on, covered with stones, and the plants set in. The procedure continues until the whole wall is finished.
Field-grown or potted plants may be used, but the latter is more easily bandied, as their root systems are compact.
Another advantage of potted plants is that they can be planted almost any time of the year except in the hot months of July and August.
Planting can even be carried out in those two months if necessary, but neither the plants nor the planter enjoys the operation.
The choice of plant material is determined, to a large extent, by the wall’s exposure— full sun or partial shade — and by the kind of stones with which it is built.
If the wall is constructed of weathered rocks, small plants which peer out of pockets and crevices, with trailers here and there, would be a good selection.
On the other hand, if the stones are more or less ordinary and were used because they were readily obtained for a retaining wall, the logical thing is to conceal them as much as possible with trailing and mat-forming plants.
Desirable Plants For Weathered Rocks
For a sunny wall of weathered rocks. Sempervivums are desirable. The tight mounds of S. arachnoideum, covered with cobwebs of fine white wool, are intriguing.
The rosettes of S. rubicund are a deep red — they lose their ruddiness even in light shade.
The common hen-and-chicken, S. tectorum, is an old standby, and in the form of violaceum, the leaves have a soft pale purple cast in late Winter and early Spring.
Not all Sedums are nuisance plants, as is S. acre. There are well-behaved members of the Stonecrop tribe — some real gems. For example, S. brevifolium has tiny gray-green leaves on tiny, twisting, red stems.
It forms a small mat filled with dainty, little white flowers in July. Another compact species is S. spathulifolium.
Grown in full sun, the gray leaves are reddish. My small plant has yet to bloom — I hope to see its light yellow flowers this June. S. spathulifolium may be grown in sun or light shade, as may S. nevi. I like this last Sedum very much. It is neat, compact, and colorful.
The small mound of gray leaves turns a lovely rose color in the Fall, and the pretty white flowers are produced freely in June and July.
Plants For Established Drywall
Sedum dasyphyllum is another free bloomer. The tight mass of roundish, gray-green leaves is almost completely hidden in the Spring with pale pink stars.
Sedum sieboldi puts on a good show in September and October when its bright pink flowers are in evidence. With a touch of pink, the arching stems of blue-gray leaves fall gracefully out of a cranny in the walled garden.
Both Sedums and Sempervivums are useful in planting established drywall. Being shallow rooted, they can lie tucked more easily into pockets and crevices than can grows with long roots.
For formats of blooms on a sunny wall, try the following:
- Arabis Alpina ‘Flore plena’
- Aubrieta deltoidea ‘Lavender’
- Dianthus deltoides ‘Albus’
- Dianthus gratianopolitanus
- Phlox subulata ‘Britton Pink’
- Phlox Cialis ‘Camlu For’
Either on the sunny side or the shaded side of a walled garden, the Campanulas will give a good account of themselves: carpatica, relatives, latines Garganega, and portenschlagiana.
Summed up, the proper way to build a walled garden is to have rocks, soil, and plants assembled on location before the project gets underway. However, an American Koek Garden Society member once said,
“I probably never would have achieved a walled garden had I waited ’till my husband, garden helper, rocks, soil, and plants all arrived at the scene of operation at the same time.
My friend, husband, and helper took care of the foundation and laid the first row of rocks; then, I covered them with soil and planted them.
The next layer of rocks went when the opportunity presented itself, and I added soil and plants. There were better ways to build this wall, and we did lose a few plants in the process. But the final results are not too bad.”
The results were not “had” at all, but very beautiful. The rocks were gracefully draped with well-flowered Alyssums, Arabis, Saponaria, Dianthus, Phlox, Campanulas, and others too numerous to mention.
The question is sometimes asked: “Can an established drywall be planted?” The answer is in the affirmative.
Planting In Established Drywall
If moist soil is rammed into the rock pockets, tiny pot plants are put in them, and a flat stone is inserted under the collar of each plant to hold it in position.
Planting this way is somewhat awkward, and it is challenging to secure the roots.
The choice of material is more or less limited to plants that can take it, but such a wall can eventually be transformed into a thing of beauty.
Friends of ours succeeded in getting foliage effects in old drywall with ferns, Violas in variety, Dicentras, Aquilegias, Kenilworth ivy, Cymbalaria pilosa, and baby wintercreeper, Euonymus fortunei Minimus.
I cite these two instances all too frequently; people are discouraged from attempting a project when they render the recommended methods and, for one reason or another, cannot adhere to them strictly.
We should heed the advice of professionals and experts and apply them as closely as our particular circumstances permit — in other words, with common sense.
44659 by Dorothy Ebell Hansell