Crab apples are typically ready to pick in late summer to early fall, usually from August through October depending on the climate and region. The best time to harvest is when the stems start to dry out, indicating maturity. Ripe crab apples will yield slightly to gentle pressure without being too soft or mushy. They also usually develop a consistent color, and may emit a pleasant aroma. Crab apples can continue to ripen off the tree if picked slightly early. Peak ripeness timing can vary, so checking the local variety and the fruit weekly during the season is advisable.