A sharp pair of hand pruners makes cleaner cuts that heal more efficiently, resulting in a healthier plant better able to fight disease, insect infestation, and natural stresses with strength and vigor.
The best way to sharpen pruners is with diamond files. Files are easier to use than whetstones, even for a novice. You’ll need three levels of coarseness (known as grits): coarse, fine, and extra-fine. The files are inexpensive and will last longer than your pruners. Well-used but well-maintained pruners should only need sharpening every six weeks. For gardeners who spend barely four hours a week pruning, one good sharpening a year may be adequate. It takes only about 10 minutes to sharpen hand pruners in relatively good condition. The more regularly you maintain your pruners, the faster the sharpening chore goes. And keep in mind that learning how to sharpen hand pruners is not rocket science. It just takes a little patience and practice.
Kitchen scouring pad
Soap and warm water
Clean rag and towel
#3 (semi-coarse) steel wool
#0 (fine) steel wool
Diamond files ( coarse, fine, and extra-fine)
A dry or silicone-based lubricant
Twigs for testing your progress
Start with a Good Cleaning
If the cutting surface is grimy, it will pass roughly over the hook and not cut cleanly, even if the blade is sharp.
Clean with a scouring pad and a little warm, soapy water, scrub off all the sap, dried plant bits, and other gunk, and wipe the blades dry.
Use the coarse steel wool to remove rust and any tough matter that remains. Then move on to the finer steel wool to restore the sheen of the metal.
Get the Angle and Motion Right
Begin with the coarsest file and progress to the finest for the best edge. Before you use any of the files, pat them with a moist cloth. The water will keep the file from clogging with the tiny bits of metal you’ll be removing from the blade.
Start with the coarse file, holding it at the same angle as the beveled cutting edge (usually between 10 degrees and 20 degrees). Starting at the inside of the blade, use moderate pressure and draw the file toward the tip in a curved motion that follows the shape of the blade. This motion is easy, safe, and sharpens the entire blade evenly. For well-maintained pruners, 10 to 20 draws with the diamond sharpener is usually sufficient, but poorly maintained pruners may need about 40 to 50 passes.
Switch to finer grits to further sharpen the beveled edge. Use the fine file first, followed by the extra-fine, using the same number of passes with each as you used with the coarse file.
Finish by removing burrs by running the extra-fine file over the back side of the blade a few times.
Finish with Lubricant
After you're satisfied with the sharpness of the blade, apply a dry or silicone-based lubricant to repel water and to hinder rust and oxidation. Once a year, apply a product made for lubricating bicycle chains. Intermittently throughout the year, lightly coat the blades with olive oil, which keeps dirt and other materials from harming the pruners without drying or becoming sticky -- and it’s a natural product.