As of 2010 there are over 20 apple rootstock varieties available. The various apple rootstocks determine not only the size of the tree, but also the fruit-bearing characteristics. Propagation of apple rootstocks is carried out by taking hardwood cuttings from the original rootstock of a particular tree. This process is called clonal propagation. Only by clonal propagation can a true offspring from a parent rootstock be grafted to different above-root apple tree cuttings in order to propagate versatile apple tree varieties. Spring is the best time to take hardwood cuttings from a parent tree, just before bud swell.
Mix equal parts of peat moss and sand into the 6-inch pot with lower drainage holes. Fill the pot to within 1 inch of the top rim.
Pour 1 qt. of water into the soil mixture. This may take some time as the water must soak into the soil medium and not overflow the rim. Allow excess water to drain from the pot's lower drain holes.
Select hardwood stems that are growing from below the graft point on the parent tree. Only small limbs that grow from below the graft point will be a true offspring from the parent tree rootstock.
Cut five stems 6 to 8 inches long as the buds begin to swell in early spring. Remove all buds from the lower 2 inches of the cutting.
Dip the cut end into the rooting hormone powder. Cover the lower 2 to 3 inches in the white substance.
Place the cuttings, evenly spaced, into the soil medium of the 6-inch pot to a depth of 3 inches.
Cut the bottom inch from the 2-liter soda bottle. Keep the upper cap in place. Fit the bottle inside the perimeter of the 6-inch pot. This acts like a mini-greenhouse to retain moisture.
Set the pot in a well-lit area out of direct sunlight. Direct sunlight will overheat and dry out the soil medium. Do not touch for three weeks.
Lift the soda bottle from the pot after three weeks. The buds should now have fully opened into green leaves. Test the soil for moisture by inserting your finger an inch into the soil medium. If dry, add 1 cup of water. Replace soda bottle. Check the soil moisture weekly and add 1 cup of water if it dries out.
Check for rooting conditions after six weeks from initial planting. Pull gently on one of the cuttings. If resistance is felt, roots are growing. Remove the soda bottle. Keep the cuttings moist. Keep in a well-lit area, and out of direct sunlight.
Plant individual cuttings into the permanent orchard area the following spring. Allow cuttings to reach a full two-year growth before grafting onto upper tree rootstock.