Plants are adaptable, and lack of a taproot doesn’t seem to be any kind of liability. Most trees don’t even maintain their taproots, at least according to the Morton Arboretum:
“10. Myth: All trees have a taproot.
Fact: Trees that germinate with a taproot eventually lose the taproot as the secondary roots grow and become more dominant. For most trees, the taproots that had initially established themselves are nonexistent when the tree reaches maturity.”
Here in the interior of Alaska, no trees have deep taproots–the ground is too cold. I’ve dug out stumps from sixty foot trees, and never observed roots penetrating much more than two feet. Elsewhere, trees send down “sinker roots” from laterals, which are able to replace any of the defunct taproot’s functions.
If you’re interested in roots, Robert Kourik has a couple of excellent books on the subject:
That’s what I was taught in hort-school and was going to write a comment similar to yours, but when I looked up tap roots and anchorage (I’ve learned to distrust old information after having my own suppositions proven wrong so often) it turns out that tap roots can be very important according to some careful and recent research. I’m thinking that even same species may behave differently in different environments and that tap roots may be abandoned in some conditions and maintained in others- but I’m only a layman. Nevertheless, I know that research in horticulture is often contradictory.
Tap roots is an interesting topic. I only have one good example to refer to and it was a callery root with several varieties grafted onto different limbs. After it was about 5-6 years old the fruit to me tasted sweeter. I eventually topped it at about 10’ and let the limbs extend outward. It grew on out a few years but I did have to keep water sprouts cut out. If you’re willing to prune this can work as a lower growing tree. We moved to another location but I’m convinced it could well outlast me.
When we relocated I dug up several plum, apple, and pear trees. These were mostly planted at the same time with dwarfing interstems in the apple and pear trees. The apples on M111 roots were spreading but were fairly easy to dig up. The Callery roots had already headed for deeper locations and it took a long time to uproot them. Eventually I had to cut some big roots and I was worried that they would die after transplanting. All six of the pear trees survived and look healthy a year after moving them. I’m convinced that the Callery is an awesome root to graft onto but they can grow very high if not checked.
I had to remove a Honey Locust which has a deep tap root. The root system was amazing considering the trunk was only 7 inches. The biggest problem was the huge tap root and the density of the wood. This is what the USDA says about Gleditsia triacanthos.
“Honeylocust is deep rooted with a widely spreading and profusely branched root system and a strong taproot. Deep soils are penetrated as far as 3 to 6 m (10 to 20 ft). The root system is responsive to environmental conditions. For example, in a Missouri study, 4- to 6-year-old saplings on upland clay soil produced root systems that were about twice as long, with laterals covering twice the area, as those of older trees growing in lowland alluvial soil where the water table was higher (7).”
Interesting. It does stand to reason that a taproot furnishes better anchorage, and where soils are leached, enables the tree to access deficient minerals. Whether a tree maintains a taproot seems mostly to be determined by species. Nothing here in Fairbanks grows a deep taproot, and I don’t think I’ve seen roots of any kind three feet down. I’ve also observed what clarkinks did with regard to fruit flavor improving as roots spread enough to gain access to better nutrition.
Referencing alan’s post on Carl Whitcomb, Whitcomb has declared that the tap root is irrelevant. I recommend his book on container plants. Of course he is the big proponent of root-pruning containers (see Root Maker containers). Some nurseries are producing really healthy trees in shallow root training bags. The theory is that finer, shorter roots are better at absorbing water and nutrients. And many sources claim that the soil nearer the surface contains more nutrients than below. I have wondered if these root-pruned trees ever do develop a tap root once planted out.
Yes, I suppose that’s possible too. But my trees’ roots would have to range about a quarter mile to find significant concentrations of water (since they can’t go far downward), so it doesn’t happen here.
Imho from digging out countless live oak seedlings, I always see one deep root, the so-called taproot, and an oval swelling closer to the surface which I surmise acts as a water reservoir for dry periods. Once the taproot hits the water table, then there is no need for the reservoir and it disappears in older saplings. That’s also when it starts forming other roots. Eventually, there will be a number of taproots depending on seasonal fluctuations of the water table and the needs of the tree, in addition to surface roots
IMHO, while anchorage may be a feature, a taproot’s main function is as an energy reserve storage vessel for young trees, allowing it to resprout, repeatedly if necessary, after being graze/browsed off by herbivores.
I have serious doubts about most taproots being able to ‘hit the water table’. Sure, it’s only about 25 ft down to the water level in the shallow well here at our house, next to the pond, but I’ll bet it’s much farther from soil surface to water table on top of some of the hills nearby.
The only nearby recorded site I could find in a USGS search of this area was at Elizabethtown, 120 miles east of me, and historically, the water table there is around 100 ft. I just do not believe that oak, hickory, walnut taproots are going 100 ft… or more… to access water.
There’s nothing magical about a taproot. Mythical, maybe, but not magical.
I agree with you. I think it serves a transient function, similar to the tooth on a chick’s beak. It helps it get out of the egg, but it disappears afterwards.
These points are all very well taken but logic persuades me to disagree partly with some of the ideas. Ever had a septic line filled with roots at 10 feet depth? Have experience with tree roots in sewage pipes because the roots went there looking for nutrients and water. Still you might doubt me but have you ever piled compost in a pile but when you used it by then it was full of tree roots? Again the roots were seeking water and nutrients. Ever been in a cave and seen roots at 20 feet depth? I have seen roots underground in caves in Missouri with the closest trees at the tops of a hollow some 40 feet above. In the same location you can here underground rivers water through sink holes in the ground at the bottom of huge hollows. That’s not to say trees can penetrate bedrock which may be a limiting factor at some locations. Proof of roots nutrient uptake is well noted. That’s not to say the taproot is not also used for resource storage for the tree. Most water I believe comes from the top 10 feet of the ground as most water comes here in the form of rain. I’m not discounting the value of deep roots either as I mentioned my callery made pears in the worst drought of my lifetime. There is still a great deal I don’t understand about roots and their different functions. https://www.nature.com/scitable/knowledge/library/water-uptake-and-transport-in-vascular-plants-103016037/
Are tree roots really so different from our arteries and veins that supply blood throughout the body? Ever damaged roots of a tree by mistake and saw part of the top die? There is a lot that I don’t think we fully understand.