fresh start
The vacuum of bare ground that surrounds a new house presents an exciting, if daunting, challenge. Define your spaces, love your soil, and dig in!
‘Paprika’
Plumbago
The soil in this magnificent Sandia foothills setting was a carefully preserved and relatively deep layer of decomposed granite, the perfect material for growing a wide variety of plants.
This article first appeared in Spring 2008 Su Casa
Ah, spring! A time of new beginnings, green shoots pushing up through a blanket of mulch, and buds bursting open as your new house stands triumphant on a denuded construction site. That last image, pristine new home surrounded by scattered clumps of stucco on hard-packed soil, gray waste streams of cement washed from wheelbarrows, and a general air of devastation is nightmarishly surreal, a landscape by Salvador Dali. Repairing the environmental damage done to the land before it can be replanted adds to the cost of landscaping, and if simply covered with landscape fabric and a few inches of rock, the degradation persists indefinitely.
You can’t ignore this nightmare on Elm Street (or in any neighborhood where new homes are being built or remodeled) as it threatens new plants and existing trees. The two greatest post-construction conundrums are compaction and pollutants. Of the two, compaction is often harder to undo. Large lots might have an extensive area intended to be left as undisturbed open space surrounding the building footprint. A succession of weighty vehicles driving over the soil during the months of construction does major damage. Uncontrolled vehicle access compacts the soil, altering its permeability and tightly compressing individual soil particles into an airless dead zone. Our native soils lack the organic matter that characterizes topsoil in wetter climates, so they may seem barren, but even desert soils teem with life. These living soils support healthy plants; they also cleanse and absorb rainwater, reducing erosion and flooding if the oxygen isn’t crushed out of them under the tires of heavy equipment. Mechanically ripping up the compacted soil after all the construction is finished is only marginally effective.
If construction ends when nighttime temperatures regularly fall below freezing, you can slowly soak the compacted areas so water percolates as deeply as possible. Repeated freezing and thawing will aerate the soil, restoring the soil structure somewhat before planting in spring. A much better strategy is preventing as much damage as possible before construction begins. Define the building envelope—the footprint of the buildings and a workspace around the perimeter—then fence the spaces where vehicles will be allowed, restricting traffic to the driveway and parking areas that will serve as permanent access. Limit heavy compaction to areas where it will do less harm and minimize damage to the soil. Preserve desirable native plants on new construction sites and existing shade trees during renovations of older homes.
The more space you leave undisturbed around plants, the better. Mature trees have roots that extend well beyond their canopies and serve two functions. The oldest woody roots are structural, allow large trees to defy gravity, and buttress them in the wind. The smaller roots farthest from the trunk absorb water and nutrients to fuel growth. Cut the structural roots, and trees become unstable; cut or smother the finer, farther-flung roots, and trees slowly decline, becoming more prone to further damage by insects and disease. The larger the tree on a construction site, the more of a magnet it will be as a shady parking place. Repeatedly driving over the roots compacts the soil, killing the roots, and weakening the tree. The older and larger the tree, the less likely it is to recover. A few hundred dollars invested in fencing can save thousands of dollars in landscaping. When healthy mature trees are lost, years of growth, their cooling shade, and the very character of the place are sacrificed.
On custom home sites, the first step in grading for construction should be skimming the top six inches of soil within the building envelope and stockpiling it to use as backfill or topdressing for the new landscaping. Any trees and larger brush cleared for building might be shredded and held as mulch for new planting. If the site is rocky, store boulders and smaller rocky rubble for reuse. Use boulders to create beds, build retaining walls, and accent plant groupings. Arrange the smaller rock rubble in dry streambeds to carry storm runoff away from the house into planted areas. Reusing materials on-site saves on dump fees and limits the fossil fuels used to haul materials. Redistributing the reserved topsoil, which contains the seeds of wildflowers and grasses native to the site, maintains a continuum and begins a garden that resonates as authentic. A garden at home with itself has strength and serenity absent in landscapes that lack a sense of place.
The other construction hazards to the future garden are pollutants. If solvents have been dumped onto the ground instead of being disposed of properly, the affected soil has been rendered toxic waste. It may be necessary to remove the contaminated soil as deeply as the solvent has seeped into it. By far the most common pollutants are the highly alkaline cement, stucco, and gypsum waste products of construction that litter building sites like confetti on New Year’s Eve. If not removed, they leach into the soil and become toxic to plants. Our soils are already high in pH. Although many native and xeric plants actually prefer naturally sweet soils to the more acidic humus-rich soils of moist climates, the extreme alkalinity of construction debris skews soil chemistry, making some essential nutrients unavailable and killing the soil microorganisms that somehow managed to survive the other perils of construction. Careful cleanup is necessary: remove all the dissolved cement trails and dust residue from torn bags and spills; pick up all stucco debris from large clods to small crumbs; dispose of pieces of drywall—anything that could significantly boost the soil pH. The gypsum recycled from pulverized drywall can be used to buffer sodium in heavy clay soils, but that is a condition peculiar to areas with very shallow ground water that salt up through capillary action or old agricultural land where mismanaged flood irrigation and extensive use of chemical fertilizers have destroyed the soil’s vitality. Unless you already have such sodic soil, avoid creating problems by removing as much alkaline construction debris as possible before planting.
As a designer, I relish the blank slate of a new construction site for the many opportunities it offers, but I’ve seen the blank looks in the eyes of new homeowners facing that vacuum of bare ground—too many possibilities can be daunting. To make sense of the expanse, start defining space with garden walls, fences, and other means of enclosure. Courtyard walls are often part of the house plans but are not built until the main construction is well under way. Take time to plot the proposed walls out on the ground, and spend some time in the spaces to see if they feel right for the uses intended. You can make any adjustments needed before the footings are poured without having much impact on the budget. Once you have those boundaries defined, move on to the pathways, patios, and other paved spaces, planning for them to drain off into planted areas during heavy rains. After traffic patterns are established, locate places where trees should be providing shade and using runoff from roofs and paving. This makes even a large plot a series of more manageable garden rooms. You can then frame your views within each space, considering how the light works through them from morning through midday to sunset, and imagine how they might be planted for color through the seasons, what density and layers of planting different spaces might need, and how transitions might be made from one area to another. When you’ve reached this stage of thinking, you are well beyond the surreal construction site and are closing in on a garden that might even impress Monet.
A widely acknowledged expert and author on regionally appropriate gardening, Judith Phillips has designed more than 900 residential gardens, collaborates on design teams for public landscape projects, and teaches a native and xeric plant class at the University of New Mexico.
A widely acknowledged expert and author on regionally appropriate gardening, Judith Phillips has designed more than 900 residential gardens, collaborates on design teams for public landscape projects, and teaches a native and xeric plant class at the University of New Mexico.