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An important practice in toxin-free (and other) turf care is to only mow with sharp blades. So how often do I have to sharpen the blades?

I'm sure that it will depend on conditions, but is there some general guideline? Is it based on area mowed? Hours mowed? After so many months?

And are there industry standards that professionals follow?

5

Depends on the mower you're using - if its just an ordinary electric hover mower with a rotary blade, or a non hover with a rotor blade, you just buy a new blade when its blunt or damaged, unless you want to put it in for a service every year, when they might do it if it needs it. If you can find someone to sharpen it, or you can do it yourself, fine, but in the UK, unless you sharpen it yourself, you won't find anyone to do it - replacement rotary blades for a flymo, for instance, are around a tenner, or £10, so not expensive, and I've only had to buy 2 blades in 30 years, mostly because they were either bent or badly chipped.

If you've got a cylinder mower, specially if its got an engine rather than being electric, its usual to have those serviced yearly by a lawn mower servicing company. The service may, or may not, include sharpening blades, that's something you'd have to ask them about. Most professional gardeners with large petrol mowers are quite capable of keeping their mowers functioning well, but not always including sharpening - if the mower is heavily used, it will be put it in for a full service yearly as a minimum. Groundkeepers are probably even more rigorous and are often capable of stripping down and replacing parts on their mowers, as well as sharpening.

As for how you know when the blades need sharpening, its impossible to predict - there's a big difference between a mower being used every day for 4 or 7 hours, and one that's only used once or twice a week. Damage may occur to the blades from stones or other objects hidden within the grass, and may cause the blades to be warped, chipped or simply blunt in parts.

If you're cutting grass all day long with a petrol cylinder mower, it'll likely need sharpening in spring and probably mid season. Otherwise, the easiest way to tell is by looking at the grass after you've finished - if the cut is uneven, then the blades need attention. If you're using a cylinder mower of any sort, inspect the top part of the cut grass - if it looks cleanly cut, then the blades are sharp, but if the ends look a bit chewed or tatty, then the blades need attention. This doesn't apply with rotary blades - they don't make a clean cut in the same way.

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    Buy a new one every year? When you can sharpen them in less than ten minutes? Wow, that's not normal around here... – J. Musser Jul 9 '15 at 22:57
  • @J. Musser That's not what I've said - I said buy a new ROTARY blade 'when its blunt or damaged' not every year - I've only ever bought two replacement blades in 30 years, so I think you've misunderstood. Blades are only about a tenner - easier to replace because its impossible to find anyone who'll sharpen them here in the UK if you can't do it yourself. So I think you're not really grasping what I'm saying... – Bamboo Jul 10 '15 at 11:39
  • @J.Musser - if you've misunderstood, then others might, so I've edited my answer to cover for that. – Bamboo Jul 10 '15 at 11:45
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    All good, Bamboo! As you've said before, lawns in the US are usually bigger than those in the UK. I have about 2 acres of lawn here at my spread, and I usually have to sharpen every couple months. Also partly due to running over all the sticks and stuff that fall from the trees. Not that it matters... – J. Musser Jul 10 '15 at 22:17
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It depends on a lot of factors but for rotary mowers, every 20 to 25 hours is a good interval to sharpen your blades. For some people that means once a year, for others twice a year. For commercial landscapers it's once or more a week.

You can also just look at the blades of grass the next day or so after mowing. If the tips have a large (1/4" or so) ragged and brown looking area instead of just a small line of brown then it's past the time to sharpen your blades. Dull blades leave cuts that don't heal as quickly, are easier to be affected by disease and require more water than lawns mowed with a sharp blade.

I keep 2 blades for my mower so I can swap them out and sharpen at my convenience. When I started sharpening my mower blades twice a year it seemed to make a big difference. The sharpening before summer seems like a good idea. Learning how to sharpen your mower blade isn't hard nor is it time consuming. There are tools available that can make it easier and faster too. Though mower blades aren't that expensive I find it more convenient to sharpen than to purchase a new one.

I have some more info on my site in the articles Time to Change Your Mower Blade and Mowing Tips for a Healthy Lawn if you're interested.

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Great answer, Bamboo. The old but best-to-cut-grass-with reel mower is easy to keep the blades sharp with a file or stone. Rotary blades need to be removed to sharpen correctly. At the very least make SURE THE SPARK PLUG IS DISENGAGED before messing with that blade!!! Rotary blades DO need to be sharpened regularly and I've gone and purchased extra blades for all rotary mowers. I take 2 or 3 in to the lawn equipment service store to have them professionally sharpened so all I have to do is change out the blade once per month or as soon as you see the grass tips getting ratty. This rattiness causes a 'dusty' look to ones lawn and could cause vulnerability to disease. If you know how to sharpen knives, pruners, hedge shears then great. DIY. Otherwise, they are not that expensive to keep extras professionally sharpened so change your blades out as often as you want! Don't forget to wipe with alcohol especially if you are doing maintenance on more than just your lawn! KEEP YOUR GRASS NO SHORTER THAN 3"!!! (if you have blue grass/fescue type lawn) Mow every day if you want but no less than once per week!

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    It was my understanding that reel mowers are really only useful for cutting/maintaining turf at shorter lengths. This would make them less appropriate for toxin-free turf management, which calls for cutting turf to 3" or more. – That Idiot Jul 10 '15 at 14:39
  • I have a reel mower and never use any "product" on my lawn. The two are by no means incompatible. I have an acre and a half and the reel mower is not motorized. – Kate Gregory Jul 11 '15 at 14:46
  • The reel mower is the best, especially if it isn't motorized. Not only do you save by not hiring gardeners, you save by not needing a therapist or even a personal trainer or gym! I've used them of course but not much. If you are unable to raise your reel mower so that you are able to brush the tips and leave a minimum of 3"...I'd get another that CAN be adjustable. Golf course lawns are not what you want for residential! A lot of golf courses use Poa annua, a short rooted, light green native grass that you DON'T want in your homes' lawns! – stormy Jul 11 '15 at 18:49
  • Kate! What a perfect workout! But are you telling me that you DON'T fertilize? At any rate you should try Dr. Earth's Lawn Fertilizer!! It is worth every penny!! It is very 'organic' and more importantly 'extended release'...This is the only lawn fertilizer that made enuf of an impression on me so that I actually remember its name!! And I am very familiar with lawn maintenance!! Are you able to maintain 3"??? – stormy Jul 11 '15 at 18:54
  • I am unable to remain quiet about the use of the word 'toxin'. Too broad of a label. Us humans are bags of chemicals: The food we eat are chemicals, the nutrients plants need are chemicals. All chemicals are not poisonous to all forms of life. No matter if synthetic or nature-made, chemicals are reduced to their molecular makeup and are neither 'good' nor 'bad'. There are GREAT 'products' out there, not many! We need to know/understand chemistry so we can lobby to get rid of or never use stuff on our lawns/gardens that IS truly contraindicated! I totally understand what you are meaning!! – stormy Jul 11 '15 at 19:06

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