I would question your assumption about the tap root. On what basis do you believe it makes any significant change to not damage the tap root? Nurseries routinely prune tap roots and mainstream woody plant physiology describe tap roots as juvenile root structures, i.e. the plant gets rid of it anyway as it grows out lateral shoots. I know a lot of specialist plant sources on the internet say all kinds of things about how fragile tap roots are and pawpaw communities seem to be part of that myth making. I just haven’t seen the evidence and it doesn’t fit well with existing science. Bottom line for me is don’t worry about tap roots.
What you do want to avoid is root girdling and direct seeding avoids that. There are other ways to avoid that, e.g. large containers as my examples above and regular root pruning if you grow in pots several years.
Well, admittedly, it is not from looking a research papers. It is more based on what I have heard from other “experts” who might very well be repeating bad information. I could definitely be wrong about it. However, in my own practice, I do still prefer to move away from common nursery methods, such as potting, repotting, and transplanting, which for me intuitively do cause stress for a plant. I totally get that for adaptive practices these methods might help us move in the directions we seek, though.
Me too, although for different reasons. Container-based growing needs much more energy and carries lots of risk for root girdling, which causes many trees to prematurely die.
As for root pruning: Ironically, you find much less of that among container-based nurseries than bare-root-based nurseries. We don’t have to read the scientific papers, because hortonomy professors like Linda Chalker-Scott from WSU does the reading and reviewing for us. It’s the main thing she does: Sifting through the literature and dispelling gardening myths. And even makes recommendations based on that plant physiology. Here’s one on the myth of fragile roots: https://s3.wp.wsu.edu/uploads/sites/403/2015/03/fragile-roots.pdf
thank you malte , very interesting document.
confirms what I also learned in a recent MOOK on trees : that when de trees are young, they have ample capacity to regrow roots, even tap root if needed.
That ability to regrow roots extend into adult or adolescent life. Woody plants react very similar to pruning of roots as they do with pruning of branches. It stimulates vigorous new growth.
so then similarly, you need to be carefull with old trees , not to cut too harshly at the risk of triggering an undesired reaction.
Example, some recommend not to cut more than 1/3 of the total volume of aerial material a given year. I would assume the same applies for roots ? (not to cut more than 1/3 of the roots at a time…)
Exactly. The larger the wound, the harder the plant will struggle to compartmentalize it and the higher chance for infections. But in early stages, dysfunctional root patterns are much more important to prune away than leaving them to develop into possible root girdlings.
I think it depends on the tree species. Oak, for example can survive tap root pruning but this is not conducive to long term stability and survival. Trees can look like they are doing fine, to us humans, until one day they tip over. Then you see that the roots were in bad shape even though above ground it looked OK. I see this happen often with landscape trees. Then they just get replaced with another, which suffers the same fate a few years later.
I think it’s best to seed a tree in place, for long term survival. However I concede that sometimes it’s more practical from a human standpoint to start the tree in a container in a more controlled environment. Either way, it’s very natural for tree seedlings to have a low survival rate. I always try to plant as many as i can for this reason.
How did it tap root pruning affect the trees you describe here? Landscape trees fail for a number of reasons that are independent of tap roots. One of the primary causes are root girdling. Another one is not bare-rooting trees and allowing a root-bound container tree to continue circling in the same place. Those kind of trees tip over one day. Both of these happen regularly, are independent of tap root development and the cause is easy to see after failure. Do you know of studies that describe failure due to tap root pruning?
I do not know of academic studies on this topic, although I would be interested to read them. This is for me more a matter of personal experience. I acknowledge that such experience is anecdotal and also that tree survival is something that involves a multitude of factors, some of which may not always be obvious to a human observer.
I know that in the mail-order nursery trade, vendors often extol the virtues of root pruning. However, for me such trees have seldom prospered. My success with container grown trees has been much higher ( I agree that pot-circling or rootbound roots are detrimental. However I tease them apart, not cut them.)
My experience is limited but it does include hundreds of trees over decades. My experiences lead me to conclude the following. All else being equal, a tree that grows from seed that germinated right where the tree grows is the strongest tree. Next, a healthy (not rootbound) container-grown seedling or sapling. Least viable: pruned bare root trees and large root balled trees. Not to say they cannot prosper; they can and especially species that are very resilient to disturbance.
But since tree planting and care is for me a lot of effort, my order of priority is as i described. I certainly will and do plant pruned bare root trees. Someone gave me a couple dozen bare root hazelnut and wild plum saplings this spring and i planted them all. I’m not going to look a gift horse in the mouth. But my propagation efforts with these species are focused on seeds planted in place and in containers.
Yes we used these type of pots in the nursery where i worked some years ago. They are useful and efficient of space. I’m a cheapskate though. I tend to use repurposed containers and leaky buckets that i get for free.
yes this version made in france has been improved with the grooves and the grid from an international model.
Indeed these pots are very expensive, but as I do not like waste I make recovery after the planting yards of gardeners in the city where I work. Nice lots of 100/200 free pots.
They are of very good quality because I have some since 5 years and they are not broken.
on an oak tree that sprouts from a seed, sometimes the tip of the root pivot necrosis during stratification.
You can cut just above even if there is no secondary root yet, and the pivot always redoes a termination without any problems.
I once asked professor Linda Chalker-Scott, who’s done extensive reviewing of the scientific literature on root girdling, on these kinds of pots (and air-pots and so on). And the answer I got, to my disappointment, was that they don’t work. The fact is that when a root hits a barrier, it will try to grow in a different direction. That might be downwards, but it might also be a U-turn, which is the beginning of root girdling. These kinds of pots unfortunately do not have science to back them up. The documentation for the producers’ claims usually come from experiments made by the producers themselves (not peer-reviewed). It’s a bummer. The saying still holds here: “A pot is a pot”
I personally like square pots for different reasons. They save space. The higher they are, the more growing space per square meter too.
Just the added grid in the background is a big improvement… the roots arrive there and are put in place with full of root bud waiting.
Never turn around or knot… of course you must use them for 1 to 2 years… not leave 20 years in.
Even if they are not perfect for the tree it’s the best solution available. I find this better than the soil culture where the main root becomes priority without making branches of roots which is annoying in the case of a transplant. This remark is related to the fact that our land here is heavy clay… in a sandy soil root divisions would be more numerous
