How deep are tree roots vs. How deep is your well ?

We are going through a dry spell and I spend a lot of time watering new, smaller trees. It suddenly occured to me that I live in a wonderful part of the world where the (seemingly unending) water table is close by. Last summer my well pump died and I tried to learn all I could from the men who replaced it. My well is 18 feet deep. My nearest neighbor (1/10 mile away) says his is 30 feet deep. How deep are tree roots? OK, I know it depends on what tree. I am concerned about Maple, Birch, E. Beech, Katsura, Tree Liliac, Magnolia, Heptacodium, Pear, Apple, Tulip, Plum, Yellowwood, Amur Cork, Ky. Coffee Tree, etc. Very sandy soil. Seems like once one of my trees reaches a certain height, it probably has its roots down to where there is water = I really do not need to water it, though it would not hurt. I know this may be a simplistic approach, any ideas?

Our well=475 feet.

Once -a long while ago this old fella told me that a large tree can drink 200 gallons day. When he said that, I stopped watering and worrying about trees. I do during times of water stress give the shrubs a drink.

I don't remember how deep ours(but I know it's not deep, we have a very high water table) is but all suggestions say to plant any tree at least 40' feet away from the well

Most trees have the majority of their feeder roots in the top 2' - 4' of soil. These roots can extended out to 2 to 3 times the size of the crown. There are exceptions. Some trees have a persistent tap root(s) so they are able to survive droughts and in very hostile conditions as well. The mesquite is one example of the latter. You need to find out what kind of root system each tree has before you decide they can go without watering. This is especially true if they have received shallow watering their entire lives. You also have to know the soil characteristics where the trees are growing because it also impacts how the roots grow.

Texas went through an exceptional drought last year. There are now millions of dead and dying trees. Even deep rooted trees (Trees large enough to have survived other severe droughts.) have died. Here on our ranch, we have our share of losses, Although the Eastern Red Cedar (A pest in this part of the country.) suffered the most casualties, we lost some deep rooted trees as well including 4 very large and very old live oak trees. There wasn't much we could do to help the trees in our wooded areas or in our pastures, but because we have a well, I was able to water the trees around the house. Some lessons learned: 1) Make a priority list of which trees to try to save., 2) Make a watering ring 2 - 3 times the diameter of the tree crown or use a sprinkler, 3) Water for hours not minutes. I still lost some trees, but I considered myself lucky that I didn't live in the city where water restrictions were put in place very early.

I read that a sycamore can pull upwards of hundreds of gallons a day.
we are on a well -- what we could do to help that tree would be spitting in the wind.

If you have water in the well at 18 feet, there must be more moisture that moves up into the shallower soil too , by capillary action.
My well is 200 some feet, to get a better aquifer- older houses ehee started with shallower wells, say fifty feet or so.. I never water trees. But bettydee's troubles do make one respect the concern.

Thanks. Guess I must have worded my question poorly as most replies are nice and good info but not exactly what I was looking for. One more try: IF the water table is X feet deep, is there a general rule for the height of a tree that has reached it and therefore, does not need me to water it? Say .5X, 1.3X, 3.3X, etc.

Trees grow roots where it is hospitable to grow roots. That (usually) requires gaseous exchange and some level of moisture. Thus, the comments above about roots typically occurring in the top 2 - 4 feet of undisturbed soils. Below that depth (in many soils) the conditions are anaerobic which is not hospitable to most trees' root growth.

Everyone can anecdotally describe situations where tree roots have "gotten into" water lines or sewer lines. This is a misnomer, which I can belabor at length with anyone wishing to e-hear it. Suffice to say, trenching for and the presence of underground utility lines can create hospitable conditions for tree root growth - primarily by loosening and aerating the soil much deeper than adjacent undisturbed soils. Secondarily, old pipes that leak water/sewage can also generate hospitable conditions, with the nutrients and moisture availability added to the loosened soils.

In your case, with ground water levels at 18 feet below the surface - I'd say you may not have any tree roots at that depth taking advantage of moisture if the conditions for tree root growth are inhospitable for them to grow to that depth. I don't know your sandy soils at all, and you haven't mentioned anything else about your climate and hydrology. Sandy soils are quite free-draining and often droughty. I'd suspect that your tree's roots don't venture very deeply, unless there is regular moisture to attain all along the way - AND, that there is the opportunity for gaseous exchange there too.

sallyg's reference to capillary action makes me want to cry. This phenomenon is more likely in soils with finer particles. Sandy soils (and in your instance, likely gravels) won't move the water nearly as high as finer soils like silts and clays - if I remember my chemistry and physics right.

May be a good question to ask an agronomist from your part of Wisconsin...

VV - thanks for confirming that, as usual, there are too many variables for there to be a simple, general rule.

(((sneaking out the back door of the room)))

Now, now - I expected to be asked about that only-slightly sarcastic remark.

If you look up capillary action, you'll see one of the examples is a very common occurrence. Crying is assisted by that very phenomenon...

LOL! Too clever for my little brain!!!

Tree roots are in no more than the top four feet of soil. That's well above the level of the water in a typical sanitary well. And wells may be dug into a confined aquifer, not directly fed by surface water above.

Maybe a more pointed question is : How would you know if your trees needed watering? Bettydee- did trees obviously wilt under such drought stress?

I have one tree that started losing leaves that had turned yellow. Looked Fall like in June.

My dogwoods do visibly wilt.

Sallyg,
It's impossible to make blanket statements when dealing with living organisms. There are too many variables and coping mechanisms vary from species to species. It wasn't just the dry soil that was extreme last year. Parts of central Texas had close to 90 (Austin had 90) days of over 100ºF temperature. On quite of few of those days the humidity was down in the single digits. Summer-like weather started early and ended late. When the temperatures weren't over 100ºF, they were pretty close — in the high 90s.

With some trees, it's difficult to tell whether the leaves are wilting or not because the cuticle is so thick. The first visible signs of stress on trees with such thick cuticles was whole branches turning brown. The drought of 2011 officially started the previous October. Trees that require lots of water were among the first to show signs of stress, but eventually all trees showed signs of stress. New growth in many species was sparse last spring. Some trees had the beginnings of whole branches dying that early in 2011. Small trees growing in dense woods were already dead or dying by the time spring arrived.

So, to answer your question — "did trees obviously wilt under such drought stress?". Mesquite trees, even with the deep and massive root systems they have, did show some wilting. They have thin and very feathery leaflets. Wilting in other trees was harder to detect until they showed obvious signs of dying. I mentioned coping mechanisms earlier. Many plants have the amazing ability to go dormant during extreme heat around here. It was one of the reasons we didn't so any spraying last year. It would have been a waste of money. Trees that appeared to have survived last year never came out of winter dormancy.

Millions of trees are dead or dying in Texas as a result of the drought last year. Trees with damaged root systems may not die immediately, but may succumb later to diseases or pests which would normally have little to no effect on healthy trees. Our live oaks will continue to show the effects of the drought by dropping large branches over the next few years.

Bettydee,
I feel bad that I'd been unaware of the extent of the drought. So sorry. It must have been awful. Thanks for the information. I sure hope this year is much better.

http://droughtmonitor.unl.edu/

Most of Texas was a very dark color for a long time. Getting a bit better now but still not right.

I read The Worst Hard Time by Timothy Egan, about the Dust Bowl. Horrible.

Betty,
That was very interesting bit of indormation. Thank you. Maybe this tropical storm in the gulf will help some.

missingrosie,

A very persistent High hanging over Texas is keeping us dry, but it looks like you may be in for some wet weather.

we need it very badly. When I check the storm's path --- NOAA said "west" then later in the day I looked and it looked straight north and perhaps n ne. that was a quick change. My well is very very deep --- but the flow into it is about 2 liters/minute --- not strong---plus we have had a very long lived drought to deal with. It sounds as if Texas has had it worse. I hope that this summer brings a ton of nice soaking rains.
I always can tell when it is really hot because we get that "dog vomit" mold. (I have heard it called that and it sure looks like it but not sure what it is) It is bright yellow and looks like its name...then it goes grey an then a dark dark charcoal/black. If you touch it it poofffff s up in a cloud, rising and spreading through the air very rapidly. It is not supposed to be harmful but I just am not comfortable with the zillions of particles ending up in my face and lungs.

We have lots of that dog vomit slime mold this year...yuck...yeah they say to just leave it alone, it doesn't hurt the plants
We had a t storm roll thru here this morn, shaking the house and serious downpour, and we could use the rain

Last Friday we had strong thunder for at least a half hour, shaking rolling waves. Nary a drop of rain.

Here's a photo of some maple roots which do not go down nearly as far as I would have expected.

Maybe I was thinking about those huge, tall power poles/towers that go across the countryside. Knew someone once who installed them and mentioned that the underground part is at least 1/2 the height of what is above ground. But, again it all depends on what kinda ground you are on.

gas - was thinking about your comment earlier. My yard looks like end October with bright yellow leaves (mostly birch and my precious katsura) on the ground.

http://davesgarden.com/community/forums/t/1269499/