Birches require supplemental watering only when they are first planted, in time of drought, or in late fall before the ground freezes for the winter. Well-established river and paper birches can handle drier than average soils for a while. In periods of prolonged drought, however, it is advisable to water them deeply periodically. If water restrictions permit, run a sprinkler for 30 to 40 minutes once a week.
Feed birches once a year in the fall. Sprinkle a granular all-purpose fertilizer on the soil under each tree out to 1 1/2 times the distance from the trunk to the branch tips (drip line). Do not allow the fertilizer to touch the tree trunks. Use 1 cup or so of fertilizer for every inch of trunk diameter. Do not fertilize newly planted trees over their first season.
To retain soil moisture and control weeds around birches, spread a 2 to 4 inch layer of some organic material over the ground underneath them. Chopped leaves, pine needles, wood chips or similar mulch, either by itself or spread over landscape fabric, will protect the tree. Spread the mulch out to 2 feet all around the trunk.
Prune birches in late summer or in winter, because cuts made in the spring tend to "bleed" profusely. Remove dead or diseased wood and branches with weak narrow crotches. Use a pruning saw for branches not easily cut with lopping or pruning shears. To insure the tree's best recovery from pruning, use only sharp tools and don't cut into the dark "eyebrow" on the trunk above the branch, called the branch collar. You may create an attractive multi-stemmed tree by planting three or more trees very close together or by pruning a young tree at ground level, forcing it to sprout several new trunks.
Updated January 16, 2002