woody – Page 14 – The Garden Professors™

Carrot-top syndrome in white pine

I know a few folks out there are starting to believe that I’m just an apologist for the nursery industry. While it’s true most of the nursery people with whom I work are hard-working folks trying to do their best to run a successful business and produce a quality crop, there are certainly some issues out there and I’ve got my share of pet peeves. One of the things really that chafes my heiney is what I refer to as “Carrot-top” syndrome in eastern white pine (Pinus strobus). White pine is one of the most commonly planted conifers in this part of the world. White pine is native throughout much of the eastern US and is an extremely fast growing tree that makes a good ornamental when planted on the right place with room to grow. It is also widely grown as a Christmas tree in the Upper Midwest as well and therein lies the rub. Many nursery producers also grow Christmas trees and many Christmas tree growers also dig nursery stock. The result? White pines that have been heavily sheared as Christmas trees end up planted as landscape trees. Once in the landscape, the upper portions of the trees will quickly resume rapid growth, with some shoots growing 2’ to 3’ or more per year; while the side shoots that had been repeatedly sheared barely grow at all. After a couple of years the net result is neatly trimmed Christmas tree with a wooly beast growing out of its top. What’s the solution? Ideally producers should identify which portion of their trees will be sold as Christmas trees and which are destined for the landscape trade. Christmas trees can be sheared to meet demands of that market while landscape trees can be pruned much more lightly to maintain a single leader and conical form but keep obvious layers of whorls. The dilemma, of course, is that growers don’t always know which trees will end up and the Christmas tree lot and which will be dug for the nursery trade. The other, more challenging problem is that, given a choice, 99 out of 100 garden consumers will choose the neat-looking Christmas tree for the landscape, unaware of the wooly mess that’s about to be unleashed in their yard. The solution? Education on both sides; making growers aware of the issue and making consumers realize that the only way to have a natural-looking white pine in your yard is to start with a natural-looking white pine.

Heavily sheared pines will retain the outline from from shearing for years while the top rages out of control.

Mysterious tree failure exposed!

end about the tree failure question! Many of you zoned in on an important point visible in the two photos I shared. The tree’s base was obviously quite narrow where the trunk broke, and with the tree’s vase-like architecture this led to breakage. But why was the base so narrow?

Again, several of you thought about root issues, such as a restricted root zone, or possible damage to the lower trunk. Actually, it’s a combination of root and trunk issues, as this last photo shows:

Tree failure 3

What we have is a large circling root (you can see it at the soil surface to the left and right of the trunk) that has girdled the trunk completely and prevented it from growing in diameter. The trunk above this point continued to grow, eventually creating the instability that eventually led to failure.

This tree used to be the focal point of a small urban landscape. It was planted about 15-20 years prior to failure and obviously had poor roots. It irks me that the industry cannot figure out a way to (a) produce trees with decent roots and (b) plant them correctly. No wonder so many ISA-certified arborists are now recommending that people only purchase bare-root trees, so that these heart-breaking scenarios are avoided.

Congratulations to Jimbo in Australia for being the first to identify this particular problem, and honorable mentions to those of you who had logical and realistic diagnoses for tree failure.

(I hate to take pleasure out of the fact that girdling roots are a significant source of tree failure in Australia, but Jeff and Bert give me so much grief about root washing that I was starting to wonder if it was only the Pacific NW that was cursed with this problem. Guess not!)

Mysterious tree failure…

Here is this week’s plant puzzler. This mature tree just fell over one summer day. There had not been any significant wind, the soil was well-irrigated (but not overly wet), there had been no construction work or other root-zone disruption. There were no significant pest or disease problems. I’ve posted two photos from different angles, and will show one more photo on Monday. Why do you think the tree failed?

Seattle Chainsaw Massacre

In the spirit of the season I’m including some photos from our neighbor’s willow tree that failed a few years ago. The failure wasn’t unexpected, given the age of the tree and the lack of crown care it received. What’s truly scary is the “tree service” that came out to deal with the problem. Low bid wins again!

(And yes, I’ll post a puzzler as well. Two for one today!)

Here’s the willow after the crown collapsed

Rickety ladder + chainsaw = suspense!

Standing in the collapsed crown – no rope or other safety equipment

Look Ma! One hand!!!

And best (worst?) of all, the remaining trunk was just left in place. It quickly resprouted and now resembles Cousin Itt from The Addams Family.

The Flap Over Burlap

This month’s issue of the Oregon Association of Nursery’s Digger magazine includes the second part of a two-part article on urban foresters’ perspectives on nursery stock. It was interesting to note that some urban foresters felt they were in a quandary because their specs require removal of burlap from B&B trees, yet many nurseries will void their warranty if burlap is removed from the root ball.

Removing burlap from B&B trees is a practice that is widely recommended, yet there is little, if any, data to support it. The logic, of course, is that burlap will prevent root egress into the surrounding soil after planting. But is this really the case? We conducted a study a couple of years ago using 3” caliper B&B green and white ash trees as part of a trial on the movement of a systemic insecticide (imidacloprid) for treatment for emerald Ash Borer. Since we were using radioactive carbon-14 as a tracer, safety regulation required us to keep the trees contained. The trees were dug with a 36” tree spade and placed in burlap-lined wire baskets by a local nursery (Discount Trees. Inc.) using their standard procedures. For the study we placed the root balls in large orchard boxes backfilled with top soil. We removed all ropes and the top of the burlap. The trees were used for a study that lasted two growing seasons. At the end of the second season we conducted whole tree harvests on a sub-sample of the trees. My vision for the root system harvest was that we would simply chain up the baskets and pop the trees out of the boxes; the burlap would help contain the roots, right? Wrong. Separating the root balls from the boxes became a major ordeal that involved a whole lotta shakin’ with the front-end loader. Once the root balls were finally extracted it was obvious that the burlap provided little resistance to root egress into the surrounding soil.

My former grad student, Grant Jones. “He said it would come out easier than that…”

Mike Kuhns at Utah State University conducted a trial several years ago (J. Arbor. 23:1-7) in which he observed a similar phenomenon. Mike compared root egress of B&B maples with burlap removed versus a single or double layer of burlap by calculating a RTRATIO which was based on the amount of the total root system weight that was found outside the original root ball. There was no difference in the RTRATIO between trees with single burlap and trees without burlap at any date during the 2-year study. Double burlap decreased RTRATIO initially but there was no difference by the end of the study. Annela et al. (Arb. & Urb. For. 34:200-203) compared various growth parameters of baldcypress, plane tree, and freemani maples transplanted bare-root or B&B with only the top of the burlap removed. After two years the only statistically significant difference was an increase in shoot growth for the B&B maples.

So what does it all mean? My personal opinion is that when it comes to establishing trees in the landscape we spend way too much time worrying about trivial matters like this. (Digging a planting hole 3X the width of the root ball and amending backfill are others but we’ll save those for another post). Matching species to site, quality planting stock, and proper after transplant care – especially mulching and irrigation – are way more important but still neglected. If we plant quality plants in the right place and take care of them properly the first two years after planting we would eliminate 80%+ of the transplant issues I see. Burlap or no is a tempest in teapot.

Building a better tree? Not in the long run!

One of the landscape tree production practices that drives me absolutely nuts is heading back trees in the nursery to create “columnar” specimens. It’s easy to find examples of these in Washington state nurseries, like the pathetic oak shown below:

Aesthetics aside, let’s focus on how the tree responds to heading back. The removal of the dominant leader encourages lateral branches below to become more upright; from these laterals, a new leader is selected. This new upright growth habit is highly prized by many landscape architects and urban planners, as such trees fit more neatly into small urban spaces without interfering with vehicle and pedestrian traffic. Sure, it works great for a few years.

Now let’s look at these trees a decade or two later. Branches grow in diameter as well as length. All of these acutely angled branches begin to grow into each other, creating bark inclusions:

What effect do bark inclusions have on the trees? These fused branches are not strongly connected; in fact, they are likely points of branch failure. As these branches become larger and heavier, they can create hazard situations if they are near people or property. What’s happening here in Washington, and probably elsewhere, is that arborists must be hired to prune out some of these branches to reduce the risk of failure and injury.

This…most definitely will lead to this…eventually

I can’t understand why this practice is perceived as “building a better tree.” To me, it looks like creating a maintenance and liability problem down the road.

EverGreen or EverYellow?

In last week’s post I mentioned that many tree problems can be difficult to diagnose and require a thorough inspection and site analysis to get to the root of the problem. In contrast, a recent issue that has generated a lot of calls is easy to explain and is not a cause for major concern. Many homeowners and others are alarmed that needles on their white pines are turning bright yellow.

“Is my pine dying?”

The key in assessing this situation is looking at which needles are turning color. Except for southern pines, most conifers produce only one, single flush of new needles each spring. Because of this, we can work our way down a shoot and tell when each group of needles was formed. The outermost needles were formed in the current year, needles in the next internode were formed the year before, needles formed in the next internode were formed the year before that, and so on. Most evergreen conifers keep their needles for 3-6 years and then the needles senesce and fall off. The longest-lived needles, perhaps not surprisingly belong to bristlecone pines, which are also the longest living trees on earth. Bristlecone pines, the oldest of which is over 4,500 years old, have needles that persist for 13 to 17 years. But I digress, back to the white pine. White pine needles last 2 or 3 years. Each fall, many of the previous year’s needles turn yellow and senesce. Since the needles often turn bright yellow and almost half the needles on the tree are affected it can certainly grab attention. As long as only older needles are turning, the process is natural and there’s no need for concern. On the other hand, if this year’s needles are dropping that’s another issue and warrant further investigation.

White pines don’t keep their needles very long. As long as this year’s needles aren’t senescing, the tree should be OK.

Pining to learn more about conifers? The Gymnosperm database http://www.conifers.org/ is an awesome and authoritative site that has information on just about every conifer known to science.

The Heartbreak of Plagiotropism…

…Otherwise known as “splayage”. When vegetatively propagating some species of woody plants, care should be taken when selecting where to take a cutting (piece of stem) to root. Propagation from terminal cuttings (pointy end up) usually results in orthotropism or a vertical growth habit. Cuttings from extremely lateral branches (those that grow parallel to the ground) can, in a few species, result in a spreading growth habit or plagiotropism.

This is not always undesirable – some species are purposefully propagated this way to maintain the prostrate habit that particular cultivar is known for. I’ve propagated lots of Buddleia over the years and don’t recall having this happen. Jeff, you were “Mr. Buddleia”* back in our days at UGA…please weigh in on this!

Floppulence
Buddleia davidii ‘Santana’, author’s garden.

Said plant was purchased from a little Mom & Pop greenhouse as a 4.5” pot with a 6” tall rooted cutting, and it went into our garden in May. It is now lolling all over its neighbors like a drunken sailor. What looks like a vertical piece in the back is simply propped up by the Canna. No big deal, just a good teaching moment.

‘Santana’ is a bit slower-growing than most cultivars of Buddleia, yet is in great demand due to the wacky variegated foliage. My guess? This is the result of repeated acts of propagation via lateral branches…cuttings of cuttings of cuttings. Not to mention the fact that it’s patented, so this guy may not only be floppy, but illegal (!). One of the purported upsides of the plant patenting process is to control the quantity and quality of propagation through licensing. But that’s another post topic for the future.

*Not to be mistaken for the pageant winner “Miss Buddleia”

Support your local arborist

A couple of weeks ago I was interviewed for the local paper about this year’s fall color. It’s pretty standard fare around these parts; newspapers, AAA, and so on want to know if we’re going to have good fall color, will it be early, will it last long. I mentioned to the reporter that we’re seeing a lot of early fall color in the maples around mid-Michigan, in contrast to the northern part of the state, which appears to be running a little late. The question of course, is why. I noted even though this summer was relatively cool, trees have been stressed the past several years and some pests, such as clearwing borers, that might not normally be major problems may be taking advantage of the situation. After the article appeared in the Lansing paper, it was picked up by the Chicago Tribune and USA Today (must’ve been a slow news day). Since then my volume of “What’s wrong with my tree?”calls and e-mails has skyrocketed. Depending on how busy I am I usually make an effort try to respond to homeowner calls. A few issues, such as tar spot on maple, can be diagnosed sight unseen; “My maple has little black blotches on the leaves that look like tar spots”. Most serious tree problems, however, require a site inspection in order to fully evaluate and diagnose the problem.

If callers and e-mailers really want to get to the bottom of their tree problems I usually tell them to contact a professional, certified arborist in their area. The International Society of Arboriculture (ISA) provides training and certification for professional arborists. In order to be certified, arborists must meet certification standards and take continuing training to maintain their certification. Being an arborist is a tough job. And the business of being an arborist is made tougher by the low barriers to entry. Anyone can buy a chainsaw, slap a magnetic sign on the side a pickup, and advertise himself or herself as a tree service. Quality, professional arborists have to pay for training, insurance, bonding, up to date equipment, and proper safety gear for all employees. It’s not a very level playing field. But for the client that is looking to save the oak tree that Grandpa planted when he moved into the house after the war, the knowledge and expertise of a professional is far preferable to the chainsaw of Joe’s Fly-by-night tree service.

To find a professional arborist in your area look in the Yellow pages under Tree Services and look for arborists that are ISA certified and insured. Also the ISA has a search feature on it’s website that enables homeowners to find an arborist based on their zip code.

Baring it all, again.

Earlier in this blog we had a rather robust discussion about the merits of transplanting trees bare-root. Bare-root transplanting has had a renaissance in arboricultural circles, based in large part on the work of Dr. Nina Bassuk and her colleagues at the Urban Horticulture Institute at Cornell.

As our bloggers noted, transplanting trees bare-root has advantages over balled and burlap trees (larger portion of the root system stays with the tree) and over container-grown trees (more natural root system development). One disadvantage of bare-root trees is the need to protect roots from desiccation during storage and handling. Also, some trees respond better to bare-root treatment than others. Nevertheless, I think we will continue to see increased interest in bare-root planting. One notable trend is planting relatively large-caliper (4” and larger) trees bare-root. This phenomenon has coincided with the development of the air spade, a tool which produces powerful a jet of air that allows arborists or nursery workers to carefully excavate an entire root system with minimal disturbance. Unlike digging a tree with a traditional tree spade, the air spade allows nursery workers to maintain virtually the entire root system when lifting a tree. Last week, my esteemed colleague, Dr. Tom Fernandez, and his Nursery Management class at MSU worked with Paul Swartz, MSU campus arborist, to lift a 10” caliper weeping white pine from our campus nursery. Members of the class took turns using the air spade to excavate the entire root system of the pine. Since the class is divided into lab sections that meet throughout the week the process was spread over several days. After each lab period exposed roots were covered with wet burlap to prevent drying. By the end of the week the tree was ready for lifting and was transported via flatbed truck to its new home at the front entrance to the MSU Horticulture Teaching and Research Center. Paul Swartz reports that he has successfully used the air spade to move several large specimens on campus and the technique is especially useful for moving trees from tight spots that can’t be reached with a mechanical spade. As more and more arborists acquire air spades look for this technique to become more common.

NOTE: Photos courtesey of Dr. Tom Fernandez.

The air spade uses a stream of compressed air to excavate roots.

Note the extent of the root system. A 90″ mechanical spade would have missed at least half the roots of the tree.

Once the roots are excavated the tree is ready for lifting.

The pine resting comfortably at its new home.