To help retain soil moisture and to discourage weeds, spread a 2 to 4 inch layer of some organic material on the soil over the root zone of your maple as far out as you are aesthetically willing to go. Chopped leaves, pine needles, wood chips or a commercial bark product will protect the roots and trunk from injury by lawnmower or weed trimmer. Spread the mulch out at least 2 feet from the trunk all around it, but do not pile it up against the trunk. As it gradually decomposes it will improve the soil under the tree, minimizing the need for fertilizer. Renew this mulch when the layer gets thin, particularly in the winter.
The shallow, fibrous roots of maples like moist soil. Water young, newly planted trees well over their first season while they become established. Once established, if maples are growing in good soil, that has sufficient organic matter in it, they will not need special watering when rainfall is normal and regular. They will need supplemental watering only in late fall before the ground freezes for the winter. In periods of severe drought or if they are in poor soil, however, water established trees deeply every week or 10 days. If water restrictions during these periods permit, run a sprinkler or drip system for 20 to 30 minutes each time. Mulch the soil under maple trees well to help absorb run-off and block evaporation of moisture from the soil.
After their first year in place feed young maples annually for 4 or 5 years. In the fall sprinkle all-purpose slow-acting granular fertilizer on the soil under the tree out to 1 or 1 1/2 feet beyond the tips of the branches (the dripline). Use about 1/2 pound of fertilizer for each 1/2 inch diameter of the trunk, measured at its base. Over many years a mulched tree will get nutrients from the decomposition of the mulch over its root zone as well. Eventually annual fertilization will not be necessary. Do not add fertilizer when planting a tree or over its first season.
Maples generally need little pruning, other than to remove root suckers and dead wood or branches that cross each other or grow too low. Since maples bleed when cut, avoid pruning in the spring when the sap is running. Do it in the late summer or fall, or in the late winter when the tree is dormant. This is also a good time to study the architecture of the young tree and correct any flaws such as a double stem. Prune away the weaker stem, or leader, to assure a single strong trunk as it matures. When the tree is fully mature, any serious pruning tasks should be performed by a professional arborist.