It's OK to break the one-third rule when you have a reason to do so, and you have a reason to do so. If you can give the little guys another week to root safely, do it.

Now if the old lawn is overshadowing the new sprouts to the point that it's laying over and starting to mat down, then I'd go ahead and mow. Mowing it will do less damage than the shadowing out will do. Otherwise, let it go.

Fall growth cycles are much slower than spring, so you may want to take a look at it in August. If it still seems sparse, overseed at that point. Fall overseeding tends to go much better and have much better survival rates.

For those of you living in SoCal, there is another place called Ontario. It gets cold there and they have different grasses. But Southern Ontario is not very specific. To me that means "south of Detroit." Can you please name the nearest big place to you?

Jumping right to the question, you can let the grass grow and grow and grow while the new seedlings come in. When you bring it back down from, say, 9 inches high, first use a string trimmer to take only a little off the top. Then a few days later, do that again and take a little lower. Keep doing that until it's 5 inches tall. Then you can mow it back to 4 inches with your lawn mower set to the highest setting. That should be your mowing height for the summer.

You learned a lot, I'm sure, from aerating, top dressing, and reseeding. Your location give you a benefit of being able to seed almost any time of year. Us southerners (USA) have to watch the heat. We cannot seed with good results in the spring.

Also you do not need to aerate or top dress. Of the two, top dressing is the biggest mistake. Grass seed grows at the top surface of the soil. It does not have to be buried under soil, straw, or anything else. All it needs is good contact with the soil. Further, adding top soil will absolutely change your drainage every time you do it. Worst case is you build a dam that prevents runoff from the house from draining away and it flows into the basement. I have pictures of top dressing gone wild - 10-12 inches high. You can aerate if you want, but it doesn't need to be done. Mother Nature does not aerate when She seeds grasses. She walks cattle and other grazing and browsing animals over it to press the seed into the soil.

Here are the basics of lawn care.

Watering: Deep and infrequent. Deep means 2.5 cm every time. Infrequent depends on the temperature. Search this forum for more.

Mowing: Mulch mow at the mower's highest setting every week

Fertilizer: First fertilizer of the year is Victoria Day, then Labour Day, then Rememberance Day.

thank you! we're just north of Toronto. good idea about trimming vs mowing.