The success of apple grafting depends first on working with vigorous scions--cuttings taken from apples of the desired cultivar and put in cold storage until needed. Healthy apple scions store as long as three months at the right temperature and moisture level. Any variations from that critical balance of temperature and humidity could cause freeze damage, dehydration or infection with mold.
Collect apple scions in late winter when trees are still fully dormant. Best weather conditions include temperatures slightly above freezing, after several days of below-freezing conditions.
Clean pruning tools thoroughly by rinsing in a bucket of water containing 1 tbsp. chlorox per gallon of clean water. Rinse tools before and after collecting wood from any individual tree. Unsterilized tools spread infections through the orchard and may pass fungi or bacteria to the scions.
Choose healthy shoots from outer and upper branches or sucker shoots growing from above the graft junction on the apple tree's trunk. Scion wood should be last year's growth--the newest wood on the tree. Cut shoots from 1/4 inch to 3/8 inch in diameter, clipping the wood off at the branch collar, the swelling at the junction with the main branch.
Divide scion stock into sections short enough to fit into large ziptop plastic bags. Gather a small bundle of scions in one hand and wrap the ends of the cuttings in a damp paper towel. Roll the bundled scions in a sheet of newspaper and place the entire bundle in a ziptop bag. Seal the bag.
Refrigerate the sealed bags at just above 32 degrees Fahrenheit until needed for grafting. Storing in the freezer compartment could kill the scions. Storing in the same refrigerator as fruit and vegetables could abort the buds on the scions, ruining any chances of successful grafting. Higher temperatures reduce the useful lifetime of the scions.