Nothing's prettier than a smooth, freshly mowed green lawn. But many lawns develop a strange white cast within days of being mowed. This sometimes is due to dull mower blades. To keep your lawn looking green, sharpen mower blades with a hand file and an oilstone. The sharper the blade, the greener and more even your lawn will be. Be careful not to bend the blade while sharpening. If the cutting surfaces get out of line, you can tear grass tips when mowing and cause the white-cast problem. Remember: when you sharpen up, the grass is always greener on your side of the street. And that's the On The House tip for today.