Do you mean how much water a tree TRANSPIRES (takes up and evaporates) or how much it keeps inside the tree body?

There is soooo much information about this on the internet that I hesitate to link you to even one resource. Perhaps if you let us know the purpose of your question, we could be of more assistance.

What kind of tree?

Dan

in the linked post .. don said: I'm planning to do a workshop in April on growing hostas in woodland landscapes and ways to deal with root competition.

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i am certain this post is consistent with such ...

i presume he is going to link how much water a tree takes up.. with the ability to garden under said tree ...

i was once told that a willow can take up 80 gallons of water a day ... and i seem to recall being mocked on said recollection .. lol ...

so ... what trees need copious amounts of water to the detriment of the plants under them ...

ken

Here is a link that might be useful: link

There are so many variables involved as to be virtually unanswerable :-) If the concern is competition from the tree roots with regards to underplanting with other, smaller plants (i.e., hostas), then it is safe to assume that regular irrigation of some sort will be required to satisfy the smaller plants' water requirements.

Suffice it to say that water consumption of larger, well-established trees is often far more than one would think :-) A mature, large Doug fir can consume upto 800 gallons a day if available but will subsist on far less as necessary (Peter Rennie, RPF Consulting Forester and Arborist). And that is often the case -- many trees will 'get by' with far less water than optimal conditions would provide.

Yes, Ken is right. I would like to give my "students" an idea of how much water is taken up through the root system of a large tree in regard to growing hostas and other flowers in a wooded landscape. This is the information I've found:

The amount of water needed by trees varies with the species, the size of the tree, the air temperature, humidity, light levels, soil type, and wind movement over the leaves. (The same is true with flowers and perennials.)

A large oak tree can draw up to 50 or more gallons of water per day. Some trees use 15 gallons of water per hour on a hot day, and some can draw as much as 150-200 gallons of water on a hot day! (WikiAnswers.com; GoogleAnswers.com) Times that by how many trees you have!

- High demand
Elm
Oak
Poplar
Willow
Silver Maple
Manitoba Maple

- Moderate demand
Cherry
Ash
Hawthorn
Hornbeam
Other maples (Sugar, Red)
Mountain Ash

- Low demand
Beech
Birch
Mulberry
Cedar
Fir
Pine
Spruce

A mature tree can use a lot of water in the growing season, but uses very little when leaves fall in the winter.

What happens when trees and other plants become water deficient???

Over an extended period, plants can become water deficient (drought). They respond by wilting, leaves yellowing, dropping leaves, slowing growth, developing modified leaves, increasing the production of absorbing roo...and eventually, death!

Important to water these areas OFTEN. The rule of thumb: "WATER, WATER, AND WATER!" Broadcast water, don't spot water!

Soil types- clay vs. sand. Because clay soils have a much slower infiltration rate than sandy soils, water needs to be applied slowly over long periods of time. At the same time, clay soils have a greater water-holding capacity than sandy soils.

Trees, plants and hostas in "heat islands" such as driveways and parking lots are particularly prone to water stress.

Mature trees which are native to a region shouldn't need any watering. If that is true, how long does it take to establish a tree suited to your climate and region if it is planted from a nursery?

Here is a slightly different perspective. If the issue is growing hostas, or really, most other plants, under a tree, my guess is that the nature of the trees root system is bigger part of the equation than how much water different trees use.

Trees that have a large number of shallow feeder roots are more difficult to grow things under than what are often referred to as deeper rooted trees.

I don't profess to be very knowledgeable on that question. You can probably find more folks who have info on that question in some of the flower gardening forums. I have a block locust that has a lot of roots near the surface in one of my beds. I seem to recall Norway maples have a bad reputation in regard to that attribute.

Flowers and decorative plants like hostas are almost assuredly going to need more frequent shallow waterings while trees will do better with deeper less frequent ones. Which ones can better coexist with the kinds of frequent waterings undergrowth plants want is kind of the question, I think.

I just got further down the board and see Don has already "been there and done that" regarding my idea. Sometimes it pays to read first and talk second. ;)