I live in midtown Toronto and have a small, west-facing front lawn about 15 x 25 feet in size. The lawn gets plenty of sun in the afternoons.
The lawn covers an area that used to be an interlocking brick patio, and it seems that the contractors put in the lawn by simply pulling up the bricks, putting down a thin layer of soil, and then laying sod on top. (Digging through a small area of the lawn very quickly reaches gravel / screening.)
For the first couple of years the lawn did okay and was fairly lush. Since then, though, it doesn’t look as healthy, especially when compared to my neighbours’ lawns a short distance away — mine is pale and somewhat ‘thin’ in large areas (there are some patches of more vigorous growth), it goes to seed quite early in the summer, and while weeds are not a big issue, I don’t get good growth of the actual grass — no matter how careful I am about watering.
I am sure that the tiny amount of soil underneath the lawn is a major factor. Grubs (which tend to be an issue in our neighbourhood) may also play a role.
What is the best approach to improving the health of my lawn, given these circumstances — short of digging everything up, putting down a ton of topsoil, and starting again?
Thank you for contacting Toronto Master Gardeners.
There are a several things that you can do to improve your soil and to improve your grass overall that should avoid starting over again. As you have recognized, the most likely cause of your poor grass is an incomplete and deficient soil system. It seems that there was not sufficient soil and organic matter under your sod so that the roots of the grass have had difficulty establishing.
The first step in improving your lawn should be aerating to open the surface of the soil creating space for the penetration of air, water and nutrients. If your lawn has more than 2.5 cm of thatch, de-thatching in spring will also allow more water and nutrients to reach the roots.
Top dressing the lawn with good quality top soil consisting of loam, peat moss and compost will improve your soil conditions. Spread this about ¼ – ½ thick with a rake so that grass is still visible and the surface is even. Over seeding the lawn (ideally in fall, but this can be done in spring as well) will also thicken the grass and prevent weed growth. Cover the seed with a light layer of good quality compost to assist germination and further improve the soil.
Make sure your lawn is mowed correctly with a sharp blade and not too short. Taller (about 3 inches) grass conserves moisture better, improves competition from weeds and reduces the effects of summer droughts. Mowing frequently to cut no more than 1/3 of the length of the shoot is also best. Keep the grass clippings on the lawn to return nutrients to the lawn and act as a natural mulch. Water early in the morning when temperatures are lower reducing evaporation and winds are generally calmer. Deep infrequent watering will encourage more deep-rooted, drought tolerant grass.
Regular fertilizing also provides valuable nutrients to grass. There are many specifically formulated fertilizers for turfgrass and if applied according to the instructions, will promote a thicker, healthier lawn. Landscape Ontario has some very good information on fertilizing that you may want to consult. See:https://landscapeontario.com/how-to-maintain-a-healthy-lawn
White grubs are the larvae of beetles. The most common kind in our area are those of the native June beetle. Grubs feed on the fibrous roots of lawn grass so if you are successful in making your lawn more vigorous it should tolerate more grub feeding than your presently stressed lawn. The beetles prefer to lay their eggs in closely cut lawns so again, mowing height is best kept high. You can hand pick any visible adult beetles. Some beneficial insects like ants prey on June beetle eggs and some parasitic wasps and flies also keep the beetle population down. Starlings and blackbirds also feed on white grubs.
January 27,2021