There's nothing prettier than a smooth, freshly mowed green lawn. Unfortunately, many develop a strange white cast a day or two after mowing. So what's the deal here? Fungus, frost, aliens? It just might be a dull lawnmower blade that rips off grass tips instead of neatly cutting. Within hours the torn tips begin drying out and turning gray, and before you know it, your green lawn looks white. Here's a tip that'll keep your lawn looking green and clean all summer long. All you need to sharpen a mower blade is a simple hand file and an oilstone. The sharper the blade, the greener and more even your lawn will be. But be careful not to bend the blade while sharpening. If the two cutting surfaces are out of line, you can still tear your grass when mowing. So remember, when you sharpen up, the grass is always greener on the "under" side. Indeed. And that's the On The House tip for today.