Despite having fertilized my back lawn and overseeded over the past few years and aerated and watered, the individual blades of grass seems to be getting thinner and more wispy, There is a large honey locust in the yard, Any idea what is gong on? The ground seems to be getting harder although there is not much foot traffic . ..sorry your site would not accept my photo
Trust you are well
Sorry to hear the results – you seem to be doing the right things
Generally thin or under performing grass is caused by one or more of the following:
fertilization, compacted soil, shade/sunlight, diseases/insects and moving/watering
There are a several things that you can do to improve your soil and to improve your grass. As you have recognized, the most likely cause of your poor grass is an incomplete and deficient soil system. It seems that there is not sufficient soil and organic matter under your sod (it being hard) 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 turf grass 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.
However, it may in fact be an issue with your honey locust tree. It may be shading the grass, contributing to insects, taking the water and nutrients from the soil, etc….and ultimately out competing the grass. Here is some information on honey locust. Does the tree appear to be healthy/sick?
Ultimately you may need to decide what you value more: the honey locust and the pleasure and shade it gives or a lush lawn. If the honey locust wins out, then either continue with a less lush lawn or consider alternatives, from shade loving plants and grasses to alternative ground covers to drought tolerant plants/varieties. See for example:
The Toronto Master Gardeners also has a number of Gardening Guides:
Good luck with your decision and enjoy!