Yellow crabapple trees are sturdy trees that once established can thrive with very little attention. They'll be happy even in sub-zero temperatures, but although they need full sun, they won't do well in very hot climates. Yellow crabapple trees are known mostly for their brilliant display of pink blooms every spring, and for the tart little fruits that develop in autumn. Start yellow crabapple trees from cuttings from mid-summer to early fall.
Select a sturdy branch growing from the main stem and cut a long piece with a pair of clean garden shears. The stem should be fairly firm green at the top and firm at the bottom.
Divide the cutting into shorter pieces about 4 to 6 inches long, making the lower cut at a 45-degree angle. This will remind you which part of the stem was the lowest part, nearest the root of the parent plant. Each cutting should be made just below a leaf node, which is where a leaf grows from the stem.
Keep the cuttings cool and damp until you're ready to plant them. Put them in a cooler or in a plastic bag with damp paper towels and keep them in the shade.
Fill a planting tray with a mixture of half potting soil and half perlite. Moisten the potting soil by misting it with a spray bottle until it's damp clear through. Set the trays aside while you prepare the cutting.
Remove the leaves from the lower half of each cutting, and dip the cut ends into rooting hormone. Plant the cuttings in the prepared planting tray to about half of their length. Plant the cutting right side up, with the slanted cut in the soil, and the straight cut above the soil.
Cover the planting tray with a large piece of clear plastic, and put it where the temperature will be constantly between 72 and 76 degrees. Put the tray in indirect light, and check the soil every day. Although the plastic will keep the atmosphere humid, the soil should be misted immediately if it appears to be drying out.
Check in about a month to see if the yellow crabapple cutting has rooted. The easiest way of doing this is to tug gently on the cutting. If you feel a slight resistance, that means roots have been established.
All the cuttings to become gradually accustomed to being in a drier atmosphere. Remove the plastic for a few minutes the first day, gradually adding time for several days before the remove the plastic permanently.
Plant the newly-rooted yellow crabapple cuttings into individual, 3-inch pots. Return them to indirect light and continue to keep the soil moist until spring. When the ground has warmed in the spring, they can be planted outdoors.