Trace a fruit tree’s overnight growth warning
One missed night delays a harvest. Start with the tree named in the morning warning and inspect the eight tiles touching its trunk before moving the sapling.
Clear the complete ring around the trunk
Walk a square around the young tree, including the four diagonal corners. Look behind the leaves for weeds, fallen seeds, machines, torches, flooring or a new patch of tilled soil. Clear obstructions without swinging an axe or hoe at the trunk itself. Keep neighbouring soil untilled during growth. If several trees share the same species, inspect each one: the species in the message does not identify a particular tree.
Distinguish a spacing problem from a missed growing night
Fruit trees need two tiles between trunks so their surrounding rings do not overlap. The game normally rejects an invalid planting position immediately. If the sapling was accepted and a warning arrived later, check what changed around it. In a greenhouse, use the perimeter area for fruit trees; fixed greenhouse decorations have exceptions, but a sprinkler or other object you placed yourself can still interfere with a growing tree.
Read the first harvest correctly
Allow 28 unobstructed growing nights. Watering the trunk does not speed this up, and Tree Fertilizer is for wild trees. Outdoors a mature tree also needs its fruiting season; a spring-planted apple tree can be mature well before fall and still be bare. In the greenhouse a mature tree can fruit year-round. Pick at least every third day if you want to avoid filling all three fruit spaces.