Quercus rubra root development

[Branching out]

Hi everyone,
I’m new to this forum but have been reading as much as I could these past few weeks since I discovered this forum and have recently gotten back into trying my hand at bonsai. In addition to starting with some younger plants that I recently purchased, I bought some Northern red oak acorns that I’m currently stratifying. I live in central Indiana and our winters can get pretty brutal and I wanted to make sure I had only a few non- cold hardy to my location- trees. I know that it will take quite some time for them to develop into any workable specimen(s) but I also wanted to get some experience working with some material on the cheap. Getting to the point, I’ve been trying to find any techniques for developing the root system of Northern red oak seedlings in the hopes that I can speed up the root development/make the root system more fibrous from the onset. I came across this “discussion” and wanted your opinions on the feasibility of this technique. Link here In short, is it a good idea or should I just try to grow out a bunch of red oaks, eventually prune their tap roots and hope for the best and keep what survives? Thanks in advance for your help and I’m looking forward to learning from all of you! - Jon

 

[Forsoothe!]

Or, sow in a shallow pot and the tap will go sideways.

 

[Branching out]

Or, sow in a shallow pot and the tap will go sideways.

Thank you for your quick response! This might be a silly question, but would you consider a shallow pot to have a depth of 2-3” or more shallow than that? Also, If I sow in a shallow pot, would I still eventually need to prune the tap root to increase the fibrous roots? Thanks again for your help

 

[Forsoothe!]

You choose how deep you want it to grow and supply a vessel that deep and make up the necessary volume by having a wider diameter. You can also offset this shallow vessel's propensity to dry out too fast by sinking it in a wider, deeper 2nd vessel.

 

[Shibui]

A sideways tap root is still just a sideways tap root. It may eventually end up as a bend in the trunk but do you really need a right angle as the first bend?
I don't grow Q. rubra but they should react like most other oaks: Initial very strong, unbranched 'tap' root. Later as the trunk develops the roots will usually start to produce lateral roots which are the tree's surface feeder roots. With the oaks I've grown from seed I germinate the acorns in a bag or shallow tray. As the new roots emerge I pinch out the tip of the initial root when they are quite young - between 1/2" and 2" and then plant in a pot. Mostly the upward shoot has not even emerged by that stage. Removing the tip of the root causes the seedling to produce a bunch of replacements just near the cut end which will give you quite good lateral roots far earlier than is natural for oaks.
When you have established lateral roots there's no need for shallow pots, boards, etc as those roots will stay as laterals. The few that head down naturally can just be pruned off during scheduled root pruning.

'tap' root can be pruned later after the tree is established but oaks I've worked with do not really like that and can sulk for a year or 2 after or even die. Early root pinching does not seem to affect them in the same way.
Shallow trays seem to be the lazy or uninformed way to produce lateral roots. Better results from proper, well timed root pruning and trees develop far better in deeper pots or in the ground.

As always, everyone will have their own favorite method, often without ever having tried alternatives. It is entirely up to you what you try.

 

[Zach Smith]

Grow the seedlings in pots for the first year. In the second year, pull from the pots, cut off the tap, then plant either in the ground or a prepared raised growing bed. Doing this will build heft in the trunk. Don't spend a lot of time worrying about creating a fibrous root system in advance of building a trunk; that can come later when you lift the large tree with its good-sized lateral roots. In fact, focusing on building fibrous roots from the get-go will almost ensure your trunks remain small forever. I'm assuming you want decent-sized trunks, and the only way to get that is to give the trees room to grow now. You'll be able to build a fibrous root system in two or three years once you have the trunk built.

 

[Branching out]

Thank you Zach, Shibui and Forsoothe! for your responses! I have a lot of acorns stratifying and will likely try each of these techniques. Last night I came across a scientific journal article from a researcher at Penn State that did research on this topic about 30 years ago. They looked at cutting the taproot after stratification (it was around 0.5-2” at the time if I remember their description right) the lateral roots or pruning both and found that pruning either root type improved the number of fibrous roots without increasing leaf size but if both types of root were pruned on the same plant then trunk diameter and leaf size increased significantly. Here is the link if you want to take a look at their data! Red oak root journal article