A practical guide to help you identify, evaluate and fix disturbed landscapes
Sometimes you can’t avoid it. As I write this, I’m reeling from the damage that the roofers did to my driveway, either from the truck that off-loaded the new shingles or the dumpster that was the repository for the old ones. The same happens to residential lawns, campus grounds and office parks during a big construction project.
Instead of worrying, put the energy to good use by planning a logical step-by-step recovery process. In most cases, the process is similar to a solid landscape design with more emphasis placed on evaluation and growing conditions.
First, resist the urge to start pulling out damaged plants and replacing them with new ones. Instead, step back and revisit the goals for the landscape. This is necessary and not a step backwards; it will pay off in the long run. In other words, it’s essential that you have a clear picture of the intent of the site. This requires putting together program statements.
Obviously, trying to re-establish turfgrass was not the best choice after new sidewalks were installed here. A better plan would be to restore the soil and plant hardy shrubs and groundcovers to discourage foot traffic.
For example, a program statement for a passageway from one building on a campus to another might be: “establish a durable surface with desirable, multi-season appeal and that facilitates human movement throughout.” This is a good foundation and allows for the consideration of changes, and provides parameters so you can measure the success of the renovation. Depending on the extent of the project, you may wish to involve stakeholders through interviews and group discussions.
Carefully evaluate the site
At this point in the recovery, especially if others have provided input, there’s a tendency to start mentioning specific plant materials for the site. However, that comes later in the process.
First, start determining what exactly took place and investigate the following:
- Was there soil compaction? If so, how severe was it? Landscape plants grow poorly in badly compacted soil that resists infiltration of water and nutrients.
- Have trees on the site experienced root loss? Root loss greatly decreases the uptake of water and nutrients, and creates openings in root tissue for decay organisms to enter and begin softening wood.
- How much soil has been deposited over the roots of trees, turfgrass and ornamentals?
- Has the topsoil on the site been removed or covered with subsoil? Replacing topsoil or covering it with subsoil decreases infiltration and nutrient availability for the replacement of plant materials.
Since most construction damage issues deal with a worsening of the soil, start with soil tests. Sketch on paper or paint on the ground where construction damage took place. Next, pull soil samples in the unaffected area, perhaps 4 or 5 feet from the damaged area and a few in the transitional space between the two areas. Take samples where you expect the roots of the new or existing plants to be. In most cases, 3 to 5 inches for turfgrass, 4 to 8 inches for perennials/ground covers and 2 feet for trees and shrubs. If in doubt, contact the soil-testing laboratory for specific instructions.
It’s inevitable that landscapes will suffer substantial damage during major construction problems. Note the wounds to the tree. Your first step in repairing the damage is to revisit the goals for the landscape and develop a step-by-step restoration plan.
PHOTOS COURTESY OF JOHN FECH, UNIVERSITY OF NEBRASKA.
Construction damaged sites tend to have deficiencies in soil organic matter content, aeration, fertility and drainage. Desirable ranges for these are 3 to 5 percent organic matter, 25 to 40 PPM of phosphorous and 150 to 200 PPM of potassium. Depending on the soil type, percentage of clay/sand/silt and the pH, these numbers can be adjusted upwards or downwards slightly. Consult with the soil-testing laboratory if the report indicates data outside of the desirable ranges. The same is true for pH. Most turfs and ornamental plants grow best in neutral to slightly acid soils, with exceptions for acid-loving plants and ones that prefer basic soils.
Gathering information via the soil test report is one thing, fixing it is another. If a soil test report indicates a deficiency in one or more areas, modification and replacement are options. The more extreme the shortcoming, the more likely that replacement is called for. If there’s doubt regarding replacement, incorporating high-quality compost is a good first step. Neutral, high-organic matter compost will help solve several problems including poor infiltration, water holding capacity and nutrient deficiency. Mix it with the existing poor soil rather than merely placing it on top to avoid creating layers of soil with different characteristics. When this occurs, water will percolate readily to the interface of the two layers and stop moving downwards, causing a perched water table, which is a highly undesirable outcome.
Once the soils have been taken care of, the tendency is strong to start replanting. While it’s tempting, resist this urge; it’s not time to plant.
Instead, proceed with your site inventory and analysis. This will be invaluable to you in coming up with new designs or getting the renovation process off to the proper start. Inventory is a simple documentation of the state of the current conditions, and the analysis is a set of value judgments pertaining to the worth and need for action on behalf of each landscape element.
Construction damage to the roots of trees or valuable ornamentals often doesn’t manifest itself until later.
For example, you would note a silver maple tree with root damage in the inventory, while observations regarding overall tree health, specific nutrient deficiencies and possible pest problems would round out the initial consideration.
While few of us can draw finished architectural renderings, everyone can draw circles and ovals to create simple bubble diagrams to identify hardscapes, trees, shrubs and masses of plant material. There’s much value in identifying where the turf, ground covers, trees and shrubs will be as a first step in choosing replacement plants.
When looking at the possibilities, consider what could be in addition to what was. For example, simple sidewalk arrangements could be configured to permit better landscape growth following construction. Match the bubble diagrams to the program statements or goals for the landscape.
Once the soil replacement/modification has been done, existing vegetation is a consideration. In some cases plants may have been removed and stored/stockpiled in a temporary nursery location before the soil was worked. Before they are reinstalled, check the irrigation system for leaks, coverage, distribution uniformity and overall efficiency. Chances are good that changes from turf to ground covers or vice-versa have created the need for a retrofit in terms of spray heads, run times and other equipment. Once the irrigation system has been revamped, stockpiled plants can be replanted, which will lower recovery costs.
Construction jobs often require moving lots of dirt. Topsoil and dirt are not the same thing. Topsoil is valuable. Work with builders to save it if you can.
Now it’s time to choose replacement plants. Using the bubble diagrams as a guide, consider the height and spread, color, bloom sequence, disease resistance and other features of the many plant options. As you wade through the choices, use right plant, right place (RPRP) as a guiding principle.
RPRP is not a simple matter; more than 20 different aspects should be considered. They include (among others) shade adaptability, drought tolerance, leaf color in summer, leaf color in fall, texture, flood tolerance and stem characteristics.
In restoring most construction-damaged residential properties you generally just need to put together a simple plan to guide you in the re-establishment of turfgrass, trees and beds.
After plants are installed and the project is a growing season down the road, evaluate the success of the renovation and revisit your goals, program statements, performance of the irrigation system, rate of growth, disease/insect/weed incidence and overall success of the recovery effort.
John C. Fech is a horticulturist, certified arborist and extension educator at the University of Nebraska.