I know it's days to weeks before we'll be able to see our entire lawns, but if you need to renovate the lawn you have, now is the time to plan.
The vast majority of lawn problems are due to poor soil preparation - insufficient topsoil or organic matter, poor grading or persistent perennial weeds. The importance of proper site and soil preparation cannot be overemphasized. The benefits include water conservation and lower maintenance inputs - including your time - during the lifetime of the lawn.
If your lawn is in poor condition or you decide to use a more drought-tolerant species, you must first remove the existing lawn. There are several methods.
1. Cut the sod to a depth of five centimetres (two inches) with a mechanical sod cutter or a sharp spade, remove it and either compost it or use it elsewhere. The finished grade will be reduced by several centimetres (a few inches).
2. Turning the sod upside down in place retains organic matter but is labour intensive. It takes several weeks to kill the sod and there is no assurance that it will be fully effective. Subsequent weeding will be necessary as well as breaking up and incorporating the now dead sod into the topsoil.
3. Repeated rototilling for a growing season retains the old sod as organic matter but takes time. It also breaks down soil structure and encourages the loss of organic matter.
4. Solarization involves mowing the lawn and then watering it deeply to encourage fast, succulent growth. Moist soil also conducts and retains heat better than dry. Cover the area with black plastic, anchoring it tightly against the soil and leave it in place until the grass is dead, three to six weeks during the heat of the summer.
5. You can also use broad spectrum herbicides like glyphosate to kill the lawn. If you have perennials weeds, you may have to reapply at least once two weeks after the initial application for a complete kill.
The size and shape of your lawn depends on household use. Observe your family at play and leisure over several weeks during the summer to determine this. Also consider the shape of your irrigation delivery pattern (current or planned irrigation system) and shape your lawn to coincide with this pattern. Outline the shape of your proposed lawn with a garden hose, set up the sprinkler, and modify the shape of the lawn until it coincides with the delivery pattern.
The lawn itself need not be entirely square or circular. Adjacent flower and shrub beds can soften the geometry. Lawns adjacent to reflective aluminum siding, white stucco or cement are particularly susceptible to drought stress caused by reflected heat and light. These are better planted with drought-tolerant ground covers.
If the site has had recent construction, remove rather than bury all building materials. This avoids problems such as poor water percolation, toxicity to plants, sinking and settling of the soil and disturbance of the final grade.
Weeds rob lawns of moisture and nutrients, shade and crowd out lawn grass and may harbour diseases and insects. If re-establishing a lawn in a previously weed infested area, if removing the old sod, water well and wait for weed seeds and rhizomes to sprout. Kill using solarization, tillage or herbicide while still small. Purchased topsoil should be screened to remove rhizomes of quack grass and other perennial weeds.
Remove and stockpile existing topsoil prior to establishing the grade. On the subsoil layer, create a two degree grade (approximately one inch drop over a run of 30 inches) away from buildings, driveways, sidewalks and patios so that excess rain or irrigation water flows away from foundations and walkways. After grading, spread a minimum of 15 cenitmetres (six inches) of topsoil containing at least five per cent organic matter. More is always better.
If sod is to be installed, the final grade with topsoil should be two centimtres (3/4 inch) lower than adjacent hard surfaces so the sod will be level with sidewalks and driveways. If seeding, final grade should be about a half centimetre below hard surfaces.
Steep slopes are difficult surfaces to establish and maintain a lawn on. Better to terrace slopes and plant with drought-tolerant ground cover material. Virginia creeper is amazingly effective.
- Sara Williams is the author of the new and revised Creating the Prairie Xeriscape, Coteau Books, available at most book stores and garden centres. This column is provided courtesy of the Saskatchewan Perennial Society (www.saskperennial.ca; email: [email protected]).
