Grass growth has slowed
Situation: I had my driveway regraded and repaved. As a result, I needed to regrade(myself) the edge of the lawn that parallels the driveway so that it isnt a cliff, but more of a slope. I did so, successfully. Instead of filling in the huge gap(and somewhat deep gap ranging from 6 inches to probably 8 inches) with the dirt that I just removed, I replaced it with pure topsoil. I figured if I were to go grass there easily, topsoil has more nutrients than the dirt that wsa there. Long story short, imagine a pot with about 6-8 inches of topsoil and grass growing.
So I planted new seed about 5-6 weeks ago. It has grown in beautifully, around 3 inches in height, give or take a half centimeter. My water regimen has been once in the morning and once in the evening and it has worked.
Question 1: The growth has all but stopped at around 3 inches. I was waiting for it to get to about 3.75 inches or 4 inches and mow it back down to 3, but it hasnt grown much in the last 2-3 weeks. Why? Nothing has changed with the water regimen. We have had a chilly spell the last week or two, temperatures gone from mid 70s or 80s, to 60s or even 50s. Why has the growth all but stopped? And how can I resume?
Question 2: Since the grass is growing on pure top soil and not natural earth, is it sturdy? Will it be sturdy enough to eventually withstand the stress of a lawn mower, and people walking on it? I know to gradually ease up on the watering, so the roots dig deeper into the soil, but will the TOPS SOIL become hardened and naturally blend in with the rest of the DIRT around it? I question this because I noticed that some animal, probably deer, kicked up a hole of top soil killing some of the grass...when I investigated, the top soil was VERY loose. I am questioning the sturdyness of the topsoil, and how the new grass will eventually respond to normal wear and tear of foot traffic and lawn mower. If I stopped watering completely, eventually, will it harden on its own?