I have a bunch of new trees that I am paying close attention to. They have been in the ground for slightly over a year. The crapes have not grown a whole lot but they look healthy. I just automatically give them a good deep soaking once a week through the hot weather. Last winter I did not water them at all. The little rain we got was enough for them. The two new trees at front are planes. They have grown like wildfire this summer. When the newest leaves at the branch tips droop a little I know it's time to water. They get a good long soak. Well established planes seem to get along on a little water but they look freshest and best in summer with regular deep soakings.

My soil is rocky and sandy. I don't know how deep it is but all my plants seem to perform best with good deep soakings.

I find trees are more 'economical' waterwise than lawns.

That's funny. Last time I was in Winchester, VA it rained so hard that water got into the camper and soaked all the bedding. Couldn't find a place to dry the sheets so had to sleep on wet beds that night. Fun. Such a wonderfully lush and beautiful region. Hard to believe it gets that hot and dry there but I'll take your word for it. Great advice on the watering.

Guess it all depends on your perpestive. Have planted about 130 trees here in 5 years. Impossible to water them all(and expensive). Those I could reach with the hose got watered for 2 years. A few I carried water to. The rest were on their own. Most of these trees were drought resistant native seedling trees raised in 5 gal pots typically planted in winter. At some point for all of them, its pretty much sink or swim. 2 years for me has been the normal cut-off, but OP's point is well taken in that it may take more than that for some trees.

Grandma:

Yes, it can, once in a while, pour down rain here. I seems that different sources have different precipitation statistics. The weather channel website says we get an average of 2.85 inches in July. Most places in the eastern half of the country get over 4 inches, some areas more than 4.5 or 5. So this is a drought area--very often.

I have lived here for 9 years. Most of the time I have been here, I have done most of my watering by carrying gallon jugs to the trees. I would load up about 65 at a time in my suburban, drive near the trees, and then carry. I have planted over 750.

This year I got 650 feet of hose and have done 95% of the watering with that. I have become expert at moving it around with a minimum of effort. As the trees get bigger, they need more water, and carrying jugs just won't do the job any more. I try to give even the smaller trees--less than 4 feet tall-about 8 to 12 gallons--to soak the soil really deep. Larger ones I will leave the hose on to soak for a half hour or more.

Newly planted trees--for the first two years--get water every week--maybe just a couple of gallons (my time is limited, so I ration a bit).

But, eventually, trees will do fine here without any watering from me. I am lucky to have good, deep soils.

--spruce

I'm impressed with your dedication.
I water for the first year and in rare instances will I intervene in the second year but for the most part the trees are on their own. We don't get 100+ degree temps though and our rainfall is probably a good bit higher than there.

Grandma:

Notice my zone and state for this post--Z5 MD. I have timberland up there in the mountains. I have plantd many hundreds of bareroot seedlings there, and never once watered a one. In 1988 we had a historic drought there, and I lost most. But other years I lost zero.

Yes, it all depends on the weather and the usual climate. I posted this topic because I have learned a lot during my process of planting and getting trees estabished here in this relatively dry climate. In a nutshell, I have learned that it can take much longer than I thought, for trees to get established. I have had my county soil survey book for several years, but I had not read it so carefully before this year's drought. The soils here have a rooting zone of 5 feet or more. Yes, it takes time for a tree to get substantial roots down anywhere near that deep. This year, in particular, I have seen dramatic improvement in how some trees have responded to the dry conditions. Those that are suffering badly, I now understand, just need a little more help for a year or two more, or in some cases, a bit longer.

My message is, don't give up!

By the way, your county ASCS, or county ag extension office should have soil survey books for your county. I have 14 acres here, and maybe as many as 6 or 7 soil types. It has really helped me to learn about them and what their capabilities are. What I have read about my soils here tells me that just about any tree that is appropriate for this zone, should, ultimately, do just fine.

--Spruce

It's worth mentioning that the essential non-woody tree roots won't go any deeper than where there is plenty of oxygen available. Not just 'won't', but 'can't'. That's why a vast majority of those roots are found in the upper volume of soil, usually in the to 10 inches or so, give or take depending upon the soil type. Deep soils are a rarity, I believe.

On the other hand, I've done excavations of root systems in the sandy coastal soil of SC. The feeder roots of forest and native trees there are very shallow, too. Probably because of the lack of organic matter in the soil at deep levels. Those huge Live Oaks? They must all have a rule book that dictates that they will grow no roots deeper than 6 inches. Crazy.

That would presumably also be lack of aeration, probably seasonally high water tables. In rainy climates the pancake root system is the norm. Deep penetration is a feature of arid climates.

Here, roots go deeper than I thought. I dug a lot of holes for locust posts--usually to 32 inches or more. Down at that level, the soil seems like clay, but it is a heavy soil with a fairly high percentage of clay. As deep as I went, when I picked up a clod from that depth and carefully broke it apart, I could see there were a fair number of roots in it. I assume from the orchard grass that covered the field, and which in the worst droughts, always finds enough moisture to stay alive, and to keep a few blades green in each clump. The soil survey book says that the rooting zone in that soil is 60 inches or more, so I was only halfway down through the "usable" soil.

But in addition, moisture can rise up into the soil from the substratum, if that is not bedrock and the soil has the right texture/structure.

Anyway, healthy trees in the woodlands around here don't die in the worst of droughts. I would like to know how deep some roots go. I once talked to Professor Edwin
White, Dean of Research of the Department of Environmental Science and Forestry at SUNY Syracuse about Norway spruce and its tolerance for droughts. He said that Norway spruce very efficiently fills up the entire rooting zone of whatever soil it is growing in. I doubt that NS is unique in that regard, but in the drought of 1988 in Western MD, Norway spruce fared as well or better than most trees. I read somewhere that trees sometimes can send roots down below the usual rooting zone of soils into the "substratum."

--spruce

Last night I dug about 8 inches into the soil three feet away from the trunk of one of my year-in-the-ground planes in order to plant a currant bush. I didn't find any roots. This tree is about 20 feet tall. I can only guess that my deep watering regimen has encouraged the roots to go deep.

Trees have different kinds of root growth/structure. It may be a little like the crowns of trees--if you look in specific places for a branch, you may find just air--there are spaces between. To some extent the same is true of roots. But, according to what Professor White told me, over time Norway spruce will fairly well fill up the available soil.

There are also large roots, and there are small roots. When I was digging the post holes and found the grass roots deep down, I wouldnt have noticed them if I had not broken the clods apart carefully and looked closely.

The careful kind of research they have done at SUNY Syracuse is impressive. Have you ever seen how when they do archeological digs they take off each little layer of soil very, very carefully and screen everything, etc., etc. Well, when the researchers at SUNY Syracuse did their rooting study of Norway spruce, they did something similar. They would cut the tree down, cut off the stump, and then go down carefully, layer by layer and track the growth of each and every root. What I say is WOW! I would love to see the results of studies like that for different species of trees growing in different kinds of soils. For Norway spruce, they did this for a number of trees growing in different soils. I am not sure what from those studies has been published.

At the time they did a number of other Norway spruce studies, one of which was a study of the growth of lots of trees by doing careful slice-by-slice dissection--so carefully, that they could track every time the leader was killed by a weevil, etc., etc.

--spruce

Trees only a year in the ground are not going to have roots three feet away from the trunk unless original rootballs nearly that big. And if not rooting out vigorously, due to common impairments like amended planting hole backfill, poor condition of stock at planting time, deformed (bound, circling, kinked) roots or dramatic textural differences between soil inside rootball and that outside of it roots may have made minimal progress into new planting site.

The common configuration in moist climates is a pancake of fine roots just below the soil surface and making up the majority of root mass, with a smaller volume of deeper growing anchorage roots penetrating more deeply. These deeper roots may have a partly necrotic appearance, like the rootstock of bracken ferns, due presumably to the comparatively airless conditions.

Deep watering does not cause the surface roots to change their depth, these always grow near the top of the soil profile, where the air is and the litter layer is (often mulch in cultivated settings). Flood-and-drought irrigation regimes may serve only to subject plantings to repeated stress episodes, soil around surface roots becoming dry and then perhaps sodden and airless in recurring waves.

I thought when you saw a lot of growth on the top (new branches, increasing height and trunk girth) the same was happening underground.

However it works my trees are happy, growing vigorously and looking better than most in the area. Definitely not stressed.

When I set up my small house trailer at my timberland, I dug the footers myself by hand. Code said I had to have the primary four dug to no less than 36 inches and they had to be 36 inches square. This is a bit more digging than one might think.

Where I dug there had been red pines growing. I had a good chance to observe the "sinker roots." I have seen that term used in technical descriptions of tree roots. Red pine has particularly pronounced or very strong sinker root growth. Other trees, not so much, some maybe not at all.

Anyway, these roots did not always go down near the stumps, but a good distance from the tree they would start straight down from lateral roots that were not that far below the surface. They would just go straight down--and I mean straight down, plumb. I dug down down to about 38 inches or so--I went a little deeper than the specifications because I didn't want to take any chances of the inspector saying I had not done them right. Well at 38 inches these sinker roots were still fairly thick and were still plunging straight down.

I have not dug down under norway spruce--I wonder if they have some similar kinds of root structure. Anyway, the red pine fared no better than Norway spruce in the terrible drought that hit that area in 1988.

--spruce