Over the last few weeks I’ve said a lot of complimentary things about the Minnesota Nursery Industry and how they’re careful to avoid situations where trees are planted too deeply. What I haven’t mentioned is that there is a reason for this. During the 1980s and early ’90s trees were usually planted deeply with lots of soil over the uppermost roots. It was just common practice. Unfortunately this practice led to roots growing across the trees stems and, when those roots cross the stem, the roots always win (as you saw in Linda’s quiz last week)! Many, many trees planted in that era have trunks which enter the ground looking like the picture below. You can clearly see the roots strangling the tree. This photo was actually taken last year on this campus!
This tree is one of the lucky ones. These girdling roots were removed, the layer of soil over the crown was removed, the crown of the tree was inspected, and it was determined that this tree could survive. Many others planted during the 80s and 90s are not so lucky — in fact, many are suffering or dead.
An outcry over the last dozen years or so, mostly from cities (St. Paul and Minneapolis), led to changes in harvest by the nursery industry, and by the landscapers who install the trees. Yesterday I received a plan for planting trees up and down a major highway here in St. Paul to review. The specs were very specific — and similar to the specs that we see now across the Twin Cities and most of Minnesota. Root flare must be at, or even above, the surface of the soil.
I don’t want anyone to get the wrong idea. There are still those who sell nursery stock with the root flare buried deep under soil in the ball, and there are landscapers who dig a hole twice as deep as the depth of the ball before planting, but it’s becoming less and less of an issue as, in general, we seemed to have learned from past mistakes.
I wish west coast growers and retail nurseries would read this. The same issue of Digger magazine (produced by the Oregon Association of Nurseries) that Bert referred to in his post on burlap had some confirming comments from municipal foresters. Here's sample: Dennis Mastlock (Boise) – "We are losing many trees due to girdling roots 10 to 15 years after planting." Mark Snyder (Eugene) – "We've all heard stories about trees we've tried to plant that are found to have roots under several inches of soil, girdling roots, wire baskets within wire baskets within containers, or other problems." George Gonzalez (Los Angeles) – "…for ornamentals, more often than not, we find trees that have been forced to grow "bushy tops" by removing the central leader and pruning up all the limbs below the crown." Nolan Rundquist (Seattle) – "Too often I see structure where the dominant lead originates from a whorl of branches that is a result of topping the young tree to establish a saleable crown." These are the types of problems I've been documenting since we began this blog and I've heard nothing from the industry on adopting a more progressive attitude towards production. Seems as though our part of the country is not yet ready to learn from past mistakes, as bad trees are still produced and we still buy them.
Thanks for posting this one! We're still dealing with buried root flares in seemingly all new B&B trees, and it's really helpful to see the post-planting consequences, and to read them explained so clearly. Makes me want to print out this photo and carry it with me to planting sites, as a cautionary tale.
It seems to me there are many problems associated with the B&B method, girdling being one of the most prominent mentioned here. Do any of the kindly professors here know if the B&B method has any positive correlation with problematic root system formation (such as girdling, j-rooting or root curling), as opposed to other container methods that don't use B&B? The pots we use down under for growing specimens on to more advanced sized, for those that aren't field-planted to grow them on, utelise either aerial root pruning or root-training grooves on the insides of the pots. The main advantages of these methods is that they almost entirely eliminate root curling problems by naturally aerial pruning new root initials that grow beyond the container, or they training all new adventitious roots downwards respectively. The idea is that the roots are kept growing laterally inside the containers, instead of curling around the inside of the containers and leading to a lot the problems we've been discussing on here of late. I wish I had some pictures to send you if what I'm describing makes no sense to anyone!? I'd be interested to here from any of you about these methods, I'm sure you would have to be aware of them. Cheers.
As an interesting aside, here's an interesting methods for planting tube stock that's gaining in popularity down under. The URL has a little link at the bottom to a video of the segment. I was troubled at first, but later blown away by the method. http://www.abc.net.au/gardening/stories/s2655211.htm
When it's done properly B&B is a pretty good technique for growing plants — but it is far from perfect. Ideally plants are transplanted twice, once from a seedbed to a "liner" field, and then again to the B&B field. This transplanting results in sliced roots which will stimulate the growth of new, finer, roots. Less transplanting means less success. The biggest problem with B&B production is that, at final harvest, only about 10 – 20% of the roots are dug up with the ball of soil. Trees will take 2-5 years (depending on the size and type of tree) to regain normal water relations and photosynthetic levels. I have had the opportunity to cut abart many balls — and typically the roots within them are well formed. However, if plants go from a container to the B&B field then problems can occur — J roots often form in containers — when the containers are moved to the B&B field problems may ensue. I am very familiar with the container growing techniques you are referring to — we use something called a "RootTrapper" which has worked extremely well for us. Unfortunately it's also very expensive
Problems like this will probably continue until Landscapers are required to be certified and tested. (Most other contractors are)And also as long as the low bid usually gets the work!!!! It costs to find the root flare in a root ball. Customers cannot get a service they don't pay for (or even know that they need).
Do Landscapers in other parts of the world have regulations that require more certification than here in the USA? Mike
A great question, Mike. Maybe Jimbo in Australia can weigh in. I agree completely with the issue of certification (since I'm a certified arborist myself). But that industry has to want to change…