Watering calculator
The first year decides whether a tree establishes. This turns trunk size, time since planting and the week's rain into gallons and a schedule. Estimates, with the working shown.
How to water a new tree
- Water the root ball, slowly. For the first few months the tree can only drink from the soil it arrived in. Trickle water directly over the ball; a bucket with a small hole, or a hose on a slow drip, works better than a sprinkler.
- Check before you water. Push a finger or a screwdriver four inches into the ball. Wet means skip a day. Container-grown root balls dry out faster than the surrounding soil, so the lawn being damp tells you nothing.
- Mulch wide, not deep. Two to three inches of leaf or wood mulch over the root zone, pulled back from the trunk, halves evaporation.
- Keep the sprinkler off the trunk. Wet bark every morning grows fungus and rot on the lower stem.
- Taper off. Once a tree has been in the ground about a year and a half per inch of caliper, it can usually fend for itself except in drought.
The calculator follows the widely used extension-service guideline of roughly 10 gallons per inch of trunk caliper per week for a newly planted tree, credits rain over the root zone, and takes its watering frequency and establishment time from University of Minnesota Extension guidance. It is a starting point, not a prescription; sandy soil needs more frequent, smaller drinks, and heavy clay needs fewer, slower ones. Planting mistakes that no amount of water fixes are in Ten planting mistakes that quietly kill trees.