Monday, July 18, 2011

Canandaigua City Tree Talk with Arborist Chris Dorn

Saturday, July 16, 2011: Sunny and pleasant morning

Attending: Bill Bross, Jack Clawson, Dave Connelly, Tom & Kathy Crocker, Caroline, Robert, Philo & Charles Gray, John Hyde, Dick Kent, Leona Lauster, Robert & Annette Leopard, Laura, Ron, Bethan & Thomas Ouimette, Dave Poteet, and Paul Reed.

Several Botanical members gathered to check out the dandelion leaved sundrop moon flowers before beginning our tour with Chris Dorn. (

Chris Dorn is the Canandaigua City Arborist who studied at Cobleskill and Cornell. Chris shared a great wealth of information and I will attempt to impart a fraction of his knowledge here. (Please feel free to make corrections or additions via comments or email and I will add them to our Canandaigua Botanical Society minutes.)

Being on Charlotte Street we learned about the Platanus acerifolia (sycamore with maple like leaves). London Plane is a hybrid of Platanus orientalis (oriental plane) and Platanus occidentalis (American sycamore). Several years ago Chris used an air chisel to find out where the roots of the London Planes were. They are under the right of ways, the sidewalk and driveways but not under the deep hard compact of the road. American Sycamore has more white than green on the base bark. The seed pods are the best way to differentiate the two. The tips of the individual seeds in the seed pods have different shapes. Often the London Plane has multiple seed pods (two together) where the American Sycamore has only single pods. There are two American Sycamores in the city – one near Gibson Street Park (Park Circle and Park Stree) and the other near Buffalo at Main. Although London Plane trees are strong urban trees they are not a choice tree in Canandaigua because of Antracnose (a fungal disease). The London Plane trees of Charlotte (80 to 105 years old) are in senescence (nearing end or winter of life). They may live another 5 to 50 years.

Chris explained that trees are essentially huge living pumps. Exhaust, salt slush and cinders hinder the healthy life of a tree. The number one cause of death to a tree is mower damage. The city of Canandaigua uses Glyphosate (Round up) to trim grass around the trees. Chris cautions that it is NOT okay to use Glyphosate around young trees with green bark. The city of Canandaigua no longer sprays trees (contaminants reach other places besides the trees) or uses injections (the tops of trees are often not reached by injections).

Oak Leaf Hydrangia

Proper planting, hydrating, and pruning are the best ways to maintain healthy trees. All city trees are planted by hand. This saves from having to call before they dig.

Chris spoke about brace roots and girdling roots. Brace roots extend down and out of the base of the trunk of a tree into the ground. Girdling roots cross over the trunk of a tree instead of growing down and should be removed since they can choke trees. Maples are famous for girdling roots causing sidewalk heaving.

brace root and girdling root

Mulching trees – Visible tree bark helps protect the tree from the elements. The “bark” underground has the purpose of taking in nutrients. Generally trees have feeding roots 12 inches deep. In forests there is a layer of leaves above a layer of last year’s composted leaves all over a thick bed of rich organic soil. Mulch can help to keep the roots cooler and keeps moisture from evaporating away from the tree roots. Mulch should not be any deeper than 2 inches and should not be right up against the visible bark of the tree. Volcano-ing mulch around the base of a tree is essentially like tying a strangling wire around it. Colored mulches should not be used since the color from the mulch seeps out of the mulch and into the food source for the tree. Red mulch makes the soil too acidic and black makes it to basic.

Chris spoke about Box Elder (true maple tree), sugar maples (sharp pointy buds) and Norway maples (flat rounded buds), and Crimson king trees. For true tree identification you need to look at the buds of a tree (11 months) as opposed to the leaves (9 months). The buds carry the genetic characteristics determining each branch of the tree.

A question was asked about Emerald Ash Borer. The EAB has been spotted in Chili and Rochester. It’s only a matter of time before it comes to Canandaigua. The expense of injections is too high to consider on city trees. Ash trees are very porous and a dead ash won’t stand much more than a year. A maple can stand dead up to 20 years.

Chris talked about his consideration in purchasing trees and explained that the city may own the right of way (area between the road and sidewalk) but that the utilities are in control of the space above the right of way. This often means that a tree which grows higher than 15 or 20 feet could be destroyed by utility lines (or access of lines). Chris spoke about the “worth” of a tree and what goes into his calculations. Damage to the root system of a tree can be just as harmful (if not more so) than damage done to the visible tree. Construction takes a toll on trees.

Chris has lists of acceptable and unacceptable city trees. As a rule a street will not have more than 70% of any one tree. The trees that rank highest on work orders are Locust and Norway maples (Norway Maples are on the invasive list, with roots – often girdling with no brace roots); followed by Horse chestnut and silver maple (which tend to be brittle in high winds and ice storms). Fruit trees and oak trees are often “too messy” to be desirable in front of city resident’s homes. Linden (basswood) trees often attract bees and aphids and are therefore undesirable as city trees. Red Oak and Beech trees have especially sensitive (ground level?) root systems and it is vital that the ground within the drip line of these trees is not upset (making them destine for trouble as street trees). Tulip and Ginko trees are two favorite varieties. There is caution to purchasing only male Ginko trees as the female Ginkos drop seed which smell like dead fish.

benign growth and scarring from damage

heaving from water damage and fire blight

When Chris came to Canandaigua there were about 500 vacant tree sites in the city. There are now only 100 vacant spots and trees are always replaced when one is removed.

Chris discussed pruning a tree for growth. A young tree should be left alone for three years – especially low branches. He showed us an example of how a cut should be made 1/16 of an inch from the collar of a branch and cautions never touching the collar itself. Chris mentioned trimming out crossed branches and dead branches. Several members expressed an interest in a future Botanical event focusing on tree pruning. Chris offered to present a pruning program and could use several city trees as examples.

Add ImageBack to the barn for Chris Dorn's book of tree specimens and refreshments.

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