Your grandpa's belief about how the roots should behave is pretty logical.

Isn't that the same reason why people advise so often to deeply water the trees' soil, let dry, repeat, and thereby avoid frequent shallow watering.

While at most times that logic might be true; just like most everything else in life. I am pretty certain that without much effort there can be found plenty exceptions to the rule.

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I have 7, still living, out of the 9 oaks that I planted in deep silty loam soil, and which are next to an overflow of a pond, drainage ditch. The expanse between the upper banks of the ditch is about 6 feet wide. The banks slant with a little tapering, the ditch depth is 3-4 feet deep.

In the rainy season the bottom of the ditch has flowing water, or the soil in the bottom is at least very wet. The sides of the ditch generally are very dry. During flash thunderstorms which drop a half inch or more water in an hour; the pond overflows into the Northern end of the ditch, at a rate which quickly fills the ditch with rushing and swirling water that most times reaches two thirds of the way up the banks, and in the worst downpour situations water fills the entire ditch especially where at the lower end of the ditch the water comes to the end of the ditch that has an even higher more abruptly straight up bank. This causes the water to suddenly crash and swirl, while gravity pulls on it to make the flow take a 90 degree turn and continue flowing on, into a small, but still relatively big for the area, culvert under the street and out again into a larger and lower elevated pond.

This area is on the west end of the mt property.

the street is an asphalt paved city street running along just on the farthest west side of the ditch.

The lot's rain runoff drainage flows on this grass covere,d previously escavated lot down toward the southwest. The land slopes mostly toward the southwest with less, but still some slight sloping toward due west. That due west location where the lot ends, and is the end near where my one gallon sized potted Scarlet oaks were planted in two double and staggered rows about 10 feet or a little more, away from and along the beginning slope of the eastern bank of the ditch.

The first year I planted the trees, I did not give them supplemental watering. That was back in the fall of 2004. For the first 12 months the rains came in seasonal times, but through the following December, January, and February of 2005 conditions were dry enough to be considered the first months of a major drought period.

In Spring of 2005 the oaks received a few rains, but not enough, and by summer of 2005 we were deep into our drought period. All of 2006 and through February of 2007 the young trees encountered sever drought conditions. Since they were oaks they continued to survive but did not grow much if any. Today the trees are still no taller than 12-14 inches tall. Our recent, overly abundant spring and early summer rains have made them fill out and produce more branching, Still they have not sent up amy fairly tall water trunks.

I would have thought that if your granddad's advice applies, these trees should by now have developed significantly deep roots and be showing at least a foot or so more top growth.

The recently drought period that only ended in February of this year, had been so bad that all over town, great numbers of huge mature, deep rooted oaks, hickories, and other such trees died. My young scarlets hung in there, but never put on much if any top growth, which the, for so long, over dry soil could not have sustained.

I have not dug up any of those trees to observe their root systems, but it is hard to believe that the roots would be abundantly and deeply developed after such drought. I do not see how their small and short canopies could feed and maintain very large of root systems.

Anyway, if your Granddad's advice holds true for these little oak trees, they should end up being some tough trees.

i dont see the logic as anything other than Darwin's SURVIVAL OF THE FITTEST....

those genetically inferior to deal with the drought will die ... those that can handle it, perhaps due to higher root growth will survive..

and there should be no love lost for the weaklings ...

ken

Thanks for the responses. Should have asked in the original post if anyone knows of any studies that have been done. My grandpa, who I referred to, studied botony as part of his PhD, but that was 50+ years ago and he's not aware of any studies.

Understand the weakest died, and the strongest survived. The real question concerns the trees that survived. Do these trees have better or worse root systems than they would have if it would have been a normal precipitation year. I would think someone would have done a study on this. Does anyone know of any such studies or articles comparing precipitation/watering and root development?

John

I don't think roots "search" for water. They will appear to grow towards areas of moisture because they only develop well with sufficient water and are retarded in areas where there isn't. The advice to water deeply to encourage deep roots substantiates that, because those trees who get frequent but shallow waterings develop shallow roots in comparison, since roots will grow best where there is adequate moisture.

Some species have developed whopping extensive root systems to handle droughts over millenia through that Darwinian theory but it's not something I can see plants doing on the short term just to "find" water. They can't make that decision, have no clue that water may be present at a deeper depth and are simply responding to the stimulus already present in the environment IOW root development in the best possible current environment.

Anything occuring to stress a seedling isn't conducive to future growth. Sometimes a tree will grow out of it, sometimes the effects are cumulative and catches up with it, sometimes the consequences are permanent.

The power company felled a huge pine tree on the front of our property they were concerned would fall across power lines. When they got it half down, I inspected the growth rings. It was like a diary of the tree's health. Some rings were quite wide and I expect those were years the tree put on growth spurts in good weather. Mid-way through the core, however, was a series of three or four rings so narrow, they were barely visible. One of these days I'll hit the library's old historic newpapers file and see if there wasn't a three year drought about fifty years ago.

Interesting thread and I'll be curious to see what others think about it. I'm a nurseryman, but not a tree expert by any long shot. So, this is only an opinion on my part.

Drought affects seedlings by killing them. Even in their natural habitats many seedlings die each year from drought (or cold or shading), otherwise far more trees would arise on each site than there was room for. Seedlings that are watered will do better by growing better, as well as actually surviving.

"The universal recommendation for watering landscape plants is, 'Water deep and less often' and 'avoid light shallow watering'. The argument against light shallow watering is that a very shallow root system will result. This does not occur as the root system is very shallow anyway. Watering during a dry period, even if it extends for two or three months, will not alter the normal root growth for the species during the remaining nine or ten months! On the other hand, consider the following situation: normal spring growth occurs, soil moisture slowly decreases and energy in the plant increases as the drought becomes more severe. The soil becomes quite dry and the plant is showing signs of drought stress (wilting, dropping of lower leaves or marginal scorch of leaves). If you water, should you water light and frequently or deep and infrequently? If watering is deep, the sudden availability of water throughout the root zone may increase activity inside the plant and stimulate a flush of growth. If this occurs, new leaves that lose moisture much more quickly will increase the total water need of the plant over the previous level. Since droughts generally occur during periods of high temperature, the problem is compounded. This greater water requirement will continue until new root growth has occurred to increase water absorptive capacity relative to the requirement of the top. This is often when considerable crown dieback occurs while the base of the plant survives.

On the other hand, if the plant is watered lightly and frequently and no new top growth occurs, the plant is provided assistance until additional rains occur, but without increasing the overall water requirement of the plant. If the plant is watered lightly and frequently, then the homeowner leaves on vacation, certainly the plant will suffer. However, the stress will be somewhat less than if the plant was never provided supplemental moisture and much less than if the plant is watered deep and a soft new flush of growth occurs."

--Carl E. Whitcomb, Establishment and Maintenance of Landscape Plants

Here is a link that might be useful: Carl E. Whitcomb

Ok, I finally had some time today to do some of my own research on this subject. From what I found, my grandpa was right. He is in his late 80's but still sharp as a whip. Below are the links and what I found:

http://www.treelink.org/joa/2003/march/03zainudin.pdf

"Unfertilized and water-stressed (F0W1) seedlings recorded the highest root length, indicating that root growth was promoted under limited water-stress treatments. The lowest root length was recorded for unfertilized plants under well-watered conditions (F0W0), indicating that low nutrient availability, coupled with well-watered conditions, depressed root growth .."

http://www.marshalltrees.com/upload/articles_files/art_64attached_file.pdf

"When first exposed to drought, the allocation of food to root growth may increase. This provides more root absorptive area per unit area of foliage and increases the volume of soil colonized."