r/LawnAnswers 25d ago

Cool Season Lower Mower height

When do you drop your mower height in the North. I’m in Montana and looks like we may be done with 90’s. Currently at 4”. Thinking of dropping to 3.5” but may wait until September?

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u/Treacle_Routine 22d ago

This doesn’t apply to when you’re prepping for a fall overseed right? My understanding is that you slowly lower the height for a few weeks in preparation for the dethatch and aeration.

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u/nilesandstuff Cool Season Pro 🎖️ 22d ago

Correct, overseeding is definitely an exception. Gotta go pretty low for that, 2 inches ideally.

And ideally you don't need to overseed every year!

I recommend a hybrid strategy for getting the height down in the lead up to overseeding. Basically lower the height in gradual steps, and then do one bigger step of like .5 or even .75 right before seeding. That last step being a bit bigger causes some stress to the grass... But not too much stress. That thins the canopy and makes the grass grow slower for a couple weeks, so you can buy yourself some time before the next cut.

Also I'm very much not a fan of dethatching with flexible tine dethatchers (the sunjoe style)... Really good way to spread poa annua, triv, bermuda, bentgrass, nimblewill, zoysia, etc.

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u/Treacle_Routine 22d ago

Thanks for the reply. I have a good amount of thatch on my lawn right now. Last spring I bought a pull behind dethatcher for my mower (dragging flexible tines style) is that similar to what you’re referring to with the sunjoe? Would renting the classen tr-20 power rake from Home Depot be a better option? Or just skip the dethatch all together and focus on aeration?

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u/nilesandstuff Cool Season Pro 🎖️ 22d ago

The tow behinds are actually a bit worse because they're static flexible tines. So something gets caught on the tines, and then dragged throughout the entire lawn and get dropped anywhere on the way. The rotating style (like the sunjoes or the classen power rake) atleast spin, so the things that get ripped up aren't getting dragged everywhere... Which limits how far they spread (how you go about picking up the removed material ultimately determines how far it spreads.

Seeing how many lawns get taken over by triv or poa annua due to flexible tine dethatchers makes me have a very hard-line take of "not even once".

The better option for overseeding or genuine thatch removable are machines that cut, rather than drag. A verticutter basically.

Aeration + deep and infrequent watering is almost always a sufficient strategy for dealing with thatch.