Nothing is more frustrating to a gardener than watching a newly installed tree or shrub slowly die. In performing “post mortem” analyses on failed landscape plantings, I’ve identified four common errors that can be easily avoided:
- inadequate root preparation
- improper soil preparation
- planting below grade
- inadequate aftercare
This blog entry will be dedicated to the first point – but before I do so, we need to understand how nursery plant production has changed over the last several decades.
A brief history of propagation
Many years ago the only way to obtain young trees and shrubs was as bare-root plants. Plants were field grown, then dug up during dormancy for storage and shipping. Bare-root trees and shrubs are usually only available during a narrow window of time, but in general these plants are healthy and structurally sound. Most importantly for our discussion, growers can see the woody root system of bare-root plants and cull those that are not well formed.
The development of containerized production methods meant that plants could be grown and sold year around. When plants are grown in a production greenhouse, they are generally started in small liner pots and gradually moved through a succession of increasingly larger pots. Ideally this is done before roots become potbound, or the roots are corrected when “potted up” (moved to a larger container). What we found, unfortunately, in a study of nursery plant quality, is that root systems are often ignored in an effort to produce large quantities of plants quickly and cheaply. It is not considered to be cost effective to examine and correct root flaws during potting up, so the entire root mass is moved into the new container. Structural root flaws are not self-correcting and will become more severe the longer they are ignored.
Based on our study, as well as evidence collected by numerous researchers and arborists, it is apparent that poor root quality is a significant problem in containerized and balled-and-burlapped trees and shrubs, at least in this part of the country. Therefore, we need to correct root flaws before installing woody plants into the landscape.
A quick intro to correcting poor root systems
Balled-and-burlapped plants have a clay rootball; despite its appearance, it is fairly easy to remove the clay simply by removing the burlap and twine and soaking the entire rootball in water. You can facilitate the process using your fingers to work out the clay, or use a gentle stream of water (Figure 1).
Once the clay is removed the root system can be evaluated. If you find woody roots that are circling, girdling, or in general not growing horizontally and away from the trunk (Figure 2), they should be pruned (Figure 3). You want to develop an evenly distributed structural root system.
Figures 2 and 3 – before and after
The pictures in this post are from my own Cercis tree, which I planted in April of 2004. This is not a great time for planting, since Seattle has notoriously dry summers. Nevertheless, that’s when I planted and as you can see from Figure 3, I had to remove close to 70% of the root system. I mudded it in well (which eliminated the need for staking), mulched, and kept the root zone well rooted. It sat for about 3 months and did nothing (Figure 4), except of course the flowers died quickly!. In July it leafed out (Figure 5), and 3 years later had doubled in size (Figure 6). It is now close to 15 feet tall and is in excellent health. Given its initial root system, it’s doubtful it would have done this well without intervention.
Figure 4 – April 04 Figure 5 – July 04 Figure 6 – July 07
(I have performed radical surgery on hundreds of tree and shrub root systems and have only lost one small shrub, whose root system is in Figures 7-8. Kind of tough to prune something as fatally flawed as this.)
9 thoughts on “Health care reform (of trees)”
I am a garden writer and do a weekly column in the Detroit News called Yardening. A yardener is a non-gardening homeowner. My readers would not follow your appropriate instructions. We need to simplify for the yardener.
Jeff, the simplest fix is to have people buy bare-root trees and shrubs (as they used to decades before). And most yardeners will not like this advice (though it's certainly the cheapest way to create a landscape). I know it's more work at the outset to bare root and correct woody roots, but the long term benefits (less water, less fertilizer, fewer pesticides, greater survival) more than offset the initial time and effort.
"Slow food" has managed to sell itself as a preferable means of cooking/dining. Somehow we need to make "slow gardening" just as appealing.
I believe that an earlier post addressed the difficulty in bare rooting larger size B&B trees, and of course with container grown trees it is nearly impossible to get to the bones of the root system.
In my thirty plus years in the industry I would hazard to guess that the other causes are far more responsible for tree death than improper root systems, though there is no doubt that it is a problem. At the root of the problem with many homeowner planted trees is the axiom "dig a hundred dollar hole for a two dollar tree" which has resulted in over digging and killing far too many trees.
On a different note, I am new to your blog, but very much impressed with the practical approach. Landscape professionals will often accuse academics of impractical advice because of their lack of "real" experience. I am happy to see information that is quite useful.
Dave, I'm glad you've found the blog (thank goodness for Garden Rant!). I would agree that there may be several reasons for tree failure (including improper soil amendment and poor installation techiques). But in our part of the country the problem of poor root systems is by far the single largest issue for tree mortality that I've seen in my 10 years of post mortem analysis. The photos I posted are the rule, rather than the exception, for nearly every tree or shrub I've planted in the last several years. Additionally, we did a study on 200 or so mugo pines and Japanese maples. Of the mugo pines, nearly 100% were judged as having fatally flawed root systems (i.e. those that would kill the tree within 10 years). The maples weren't much better. Mass production methods are creating these root systems and if the industry doesn't address it, then consumers have to. I'm hoping Jim Flott (the former city arborist for the City of Spokane) will also post, as he's been doing this for many years and can address the practical issues of bare rooting large trees.
Yowser! That's some root mass on the last little plant! Here in Massachusetts root issues are a huge deal. The Mass. Arborists' Association just had a workshop on bare-rooting trees with air tools and by hand, and Matt Foti, one of the demonstrating arborists showed a number of root balls that are typical of what comes onto the market in balled-and-burlapped form. (To see photos, look at this link:http://takingplaceinthetrees.net/2009/09/16/elm-bank-workshop5-root-forensics/)
Bare-root planting is a great way to go; we have a scarcity of nurseries here that will supply plants bare-root, though. Root-washing, or bare-rooting with an air tool, can work well, but on a site where lots of plants are needed, and quickly, bare-root plants from a nursery would be the simplest route to take, if they were more available.
Deb, in a perverse way I'm glad root issues are a problem in Massachutsetts. I seem to be fighting an uphill battle, as apparently some other parts of the country don't see the problems you and I do. Why there is such a geographic discrepancy in root quality is a mystery. Or perhaps it IS a problem, but no one's looking into the root balls as closely?
Beats me. Arborists here know about the problem of buried root balls, and lament it, and some landscape architects are aware of it — but lots of contractors have no idea about it, and they're the ones who would ideally be doing the remediation (unless, in some future paradise, remediation becomes unnecessary). Contractors are trying to get their plantings done quickly, to keep costs down and profits up, and having to attend carefully isn't a happy prospect. A contractor working on a tiny planting yesterday told me that he didn't know how he could check all the root balls, remove wire baskets and burlap, and fix depth problems on a job of any size — it takes too much time to be profitable. I guess the trick is to keep looking, and documenting, and then writing and lobbying the various professional organizations to urge/make changes in industry practices.