My husband is going back and forth about mulching these leaves; he’s worried about it killing the grass we spent growing this summer. Is that a thing?
I’ll let you know next spring. I mulched down about 4-5 times that amount in half the square footage in the past month. 
Pretty sure my neighbors think I’m nuts. Well, I’ll show them when all my grass is dead and I don’t have to mow no more.
Edit: you’re likely fine. Give her 2-4 laps to really dice 'em up. You’ll see it all settle down below the blades of grass.
@Luca
We just fixed our grass back here this summer, so I understand his concern but… we grew it ourselves and still have the seed, so… we can grow it back next summer if things go bad.
Jules said:
@Luca
We just fixed our grass back here this summer, so I understand his concern but… we grew it ourselves and still have the seed, so… we can grow it back next summer if things go bad.
If your dog is like mine, you’ll be overseeding every year anyways from wear and tear. I’d definitely mulch it.
@Avery
He’s the reason we finally started working on the yard. When we moved in, the sod that was laid had never taken, and chunks would come up whenever we raked. Then our dog thought it was his official job to remove the rest of it…
Nope, that’s not even that much. Don’t know why he thinks mulching leaves would kill the grass; it won’t.
Jai said:
Nope, that’s not even that much. Don’t know why he thinks mulching leaves would kill the grass; it won’t.
I think he was trying to think of any excuse to NOT try it. His actual question was, “but aren’t there certain leaves that we SHOULDN’T mulch?”
@Jules
Nope, they all decompose anyway; mulching just makes it happen faster, which in turn provides useful nutrients to the soil.
Jai said:
@Jules
Nope, they all decompose anyway; mulching just makes it happen faster, which in turn provides useful nutrients to the soil.
Won’t the grass get smothered and die if you DON’T mulch?
@Jules
No bad leaves for a lawn. Run over them twice in a crossing pattern to more finely chop them up.
It’s a heck of a lot easier than bagging them and emptying the bagged every couple of passes because it’s full of leaves so fast.
@Jules
The thing I learned this year is to let them sit for a few weeks.
Currently, they are as big as they’ll ever be. Once they shrivel up and dry out, they will crunch and break up. Two to three passes and they will disappear in the grass.
Mulching leaves into the lawn is tremendously beneficial for several reasons:
- provides organic matter to the soil (good for nutrient and moisture retention, alleviates compaction, and improves drainage in the long term)
- provides the lawn with many nutrients that are difficult and expensive to supply otherwise… Particularly, but not limited to, all of the micronutrients. (Trees are just way better at taking up nutrients than grasses are)
- is an incredibly effective form of pre-emergent weed control… Extremely effective for preventing broadleaf weeds and can even prevent/reduce future poa annua and crabgrass.
According to MSU, up to 6 inches of leaves can be mulched into a lawn at one time. That number partially depends on your mower performance… But even in the worst-case scenarios, it might just mean going over the leaves multiple times. (Still quicker than raking or bagging)
Tips for mulching leaves effectively:
- go into fall at a high mowing height… It’s too late to change that now, but it helps.
- use an actual mulching blade (most new push mowers come equipped with mulching blades. Mulching blades are the ones with the curved cutting edge and the blade has curved surfaces on top to generate uplift)
- plug the side discharge chute. Push mowers usually have a flap that’s easily closed. Riding mowers often require a separate accessory to plug the chute.
- don’t let the leaves pile up. Most of the time, weekly will be enough, but if you have windy days, you might need to get out there an extra time or more.
- do it when the leaves are mostly dry. It can actually help if they’re a LITTLE wet… But dry is certainly better than too wet.
- Yes, you can safely mulch pine needles and walnut leaves. It’s a myth that pine needles acidify soil. There’s insufficient proof that juglone from walnut trees is actually allelopathic… Regardless, spread out over a lawn, that wouldn’t be a concern.
- if you notice clumps of matted leaves… Knock them loose. I usually just kick them, but a rake or blower works too.
The classic argument against mulching is “they’ll smother the grass”… Simply put, if you smother the grass, you’re doing it wrong (especially that last step)… Unless you’ve got a lot of poa trivialis or poa annua… Mulching leaves can actually smother those… In which case, that’s usually a good thing… But even then, they’ll still fill back in next year.
Note: Don’t mulch leaves if you plan on dormant seeding… The weed prevention thing I mentioned above also PROBABLY applies to ungerminated grass seed… Probably. Inconsistent data on that one.
No, at my old house I had 7 trees, on a corner lot where everyone’s leaves blew into my yard and had a fenced-in backyard so my yard would be covered with 2-3’ of leaves. I mulched once a week up to and into December. Might take a couple times each mow, but that’s definitely not too much.
You may have to do three or four passes but that’s not a huge yard. Done properly, it shouldn’t take more than 90-ish minutes.
Speed isn’t your friend in the sense that if you try and run through it, it’ll mulch less with each pass. Like good BBQ, low and slow is way more effective.
And not low like “scalp-the-grass” low, just take your time. Casually walking through three passes will accomplish more than running through five.
What about these leaves? Can I mulch these leaves?
What about those leaves? Can I mulch those leaves?
As long as you shred it to small enough pieces (<dime size) and can still see grass blades sticking up, you should be good.
MIL’s house has a strip of land of just woods, and they pour leaves onto her lawn. Her record for bagging is 80 bags, and I was able to mulch the entirety of her half-acre lot. Get to work!
I believe Cornell did a study on mulching leaves. They found it to not be detrimental to the lawn to mulch leaves into it. They also found it isn’t as beneficial as once believed. I’ll see if I can find that study.
@Blair
It’s not the study I read, but still holds true:
Mulching leaves is actually beneficial for your lawn. While it might take a few passes in different directions to fully break them down, it is a great alternative to bagging. Mulching clears leaves that would otherwise smother your grass and turns them into fine, dust-like particles packed with nitrogen. This provides a natural boost your grass will thrive on.