Trunk size + age + season
Watering calculator
How many gallons, how often — based on trunk size, how long the tree has been in the ground, and the current stretch of Kansas weather. Stops both underwatering and drowning in clay.
“Water it well” is the least useful instruction in gardening, because it means a bucket to one person and a sprinkler left on overnight to another. The care hub publishes an actual figure instead — gallons per inch of trunk diameter — and this works that figure out for your tree, shows the multiplication rather than hiding it, and pairs it with the interval that goes with the tree’s age.
Weather changes how often, not how much. There is no hidden factor here that scales a published number up because it is hot: a tree that is thirsty needs a full soak, and a tree that is not needs nothing. Under restrictions the question stops being how much and becomes which trees, which the care hub answers by what cannot be replaced.
There is no soil dropdown, deliberately. Kansas clay does not change the number of gallons a tree needs — it changes how slowly you have to pour them and how long they then sit in the root zone. The site’s own answer to soil is a physical measurement rather than a menu: push a long screwdriver into the ground after you water and see how far it goes. That test is in the results, and it is worth more than any of the arithmetic above it.
The failure mode here is excess
Measure straight across the trunk, or wrap a tape around it and divide that figure by 3.14. An estimate to the nearest inch is enough.
Enter a trunk diameter, pick the stage, and say what the weather is doing.
Our tools provide general education based on your answers. They are not a diagnosis, a safety inspection, or professional advice.
Honest boundaries
What this cannot tell you
This is one published rule, multiplied by a trunk diameter and paired with an interval. It is a good default and a poor substitute for looking at the soil.
Whether the soil is actually dry right now
This is the question the whole thing turns on, and a calculator cannot answer it. Dig down four to six inches at the drip line before you water. Soil that is still damp down there means the tree is not thirsty, whatever the weather has been doing — and watering it anyway is how roots suffocate in Kansas clay.
What your particular soil does with the water
Tight clay, builder's fill, a low spot that holds water, or a thin soil over limestone all change how long the same number of gallons takes to reach the roots, and how long it then sits there. The care hub publishes no soil multiplier and this tool invents none. The screwdriver test is what accounts for your soil: it measures the result rather than predicting it.
How much rain you actually got
A storm that reads as an inch on the forecast can arrive as run-off on compacted ground and reach almost nothing. A rain gauge in the yard, and a hole dug at the drip line afterwards, both beat an assumption.
What your irrigation system is already doing
Lawn irrigation runs on a schedule built for turf — frequent, shallow, and aimed at the top few inches. It rarely reaches tree roots and can easily keep the root zone permanently damp. A tree inside an irrigated lawn is often getting the wrong watering rather than none.
How thirsty this particular species is
Drought tolerance varies enormously across the Kansas library — some of these trees ride out a normal dry spell once established and others struggle without help. The figures here are the general rule for a tree of this size and age. The species profiles carry the species-level answer.
Whether water is the problem at all
A pale or thinning crown has several possible causes that look alike from the ground, and two of the most common in Kansas are high-pH soil locking up iron, and roots damaged by something that happened years ago. Watering a tree that is not short of water fixes nothing and can make things worse.
Treat the gallons as a target for a soak you have already decided the tree needs, never as a schedule to keep regardless. The number that decides whether to water at all is the one you get by digging a small hole at the drip line, and the number that decides whether it worked is how far a screwdriver goes in afterwards. Both of those beat this calculator, and both are free.
Keep going
The guides behind these numbers
Every figure here is read straight out of the care hub's watering section, and the pages below carry the reasoning this tool only applies.
- Tree care basicsThe watering section these figures come from, in full — plus mulch, pruning, and root protection.
- Month-by-month calendarWhat each Kansas month asks for, including the stretches where watering matters most.
- Yellow leavesWhere too much water and too little water end up looking identical, and how to tell them apart.
- Brown, crisp leaf edgesWhat genuine drought stress looks like on a leaf, and what it looks like when it is something else.
- Kansas species directoryFilter by drought tolerance to see which trees actually need this and which ride out a dry spell.
- Planting guidesGetting a tree into Kansas clay so that the first three summers of watering are not wasted.
Kansas Tree Guide is an independent educational resource. Nothing on this site replaces an on-site assessment by a qualified arborist or tree-care professional. Last reviewed August 2026.