Tree of the Month

American Elm • Ulmus americana

American Elm, Ulmus americana; by Lesley Bruce SmithIt seems a fitting photograph of this month’s highlighted tree to be taken on a late winter day.  The embattled American Elm (Ulmus americana) was one of America’s best loved and most widely planted species.  Foot traffic, pollution, concrete and even nearby building construction could not knock out this rugged urban champion that can handle all kinds of human abuse. Unfortunately, what we humans failed to do directly, a little beetle from Holland managed with little difficulty.  That is why so many cities were denuded of their urban forests when hit by the fungal organism of Dutch Elm Disease. The beetle arrived in a shipment of furniture from Dutch country which was transferred from ship to train in New York and traveled west.  We can trace the spread of the disease (which is not a problem for the European Elms who co-evolved with the fungus) all along the iron rails across America.  It was transmitted on the the tiny feet of the beetles that escaped the train all along the route.  However, in spite of all the struggles we have endured with this species, it is not hard to see why it is a favorite, with its spectacular cathedral like arching branch structure that so elegantly graced many American boulevards in the last century.  

The American Elm is a native of North America, as her name suggests.  The bark tissue was used in combination with the Slippery Elm (Ulmus rubra) by the Cayuga aboriginal peoples in the child birthing process to prevent inflammation and soothe torn membranous tissue.  

The lesson this month’s tree has for us is that species diversification in our urban forests is a must, yet  it is a lesson slowly learned as we continue to plant too many of the same species, creating the set up for another catastrophic loss.  For Elm lovers in the present, much research has been done in cultivating disease resistant varieties of American Elm, many of which were created right here in Illinois at the Morton Arboretum by Dr. George Ware.

read more in Arboretum America by Diana Beresford-Kroeger

Does the snow harm my trees?

Being a “wet blanket” is a good thing.

Backyard Wisdom by Gilbert A Smith 

ISA Certified Master Arborist

Snow cover early in the winter is very good for your trees and shrubs.  It acts as a wet blanket for your trees, insulating the soil from freezing, while slowly melting and watering roots. This allows a whole riot of activities that are essential to tree health.  If we don’t have snow cover, it’s even more important to leave the natural leaf litter beneath the tree canopy, because leaf mulch, like the snow is an insulating blanket that keeps the soil warm and biologically active. (click here to see Mulching Abstract)

So what is going on beneath the snow white cover?  You’ll be shocked to know that there is a mating dance happening between tree roots and fungi in the soil.  The fungi need sugar for food to survive and the trees have those sugars stored in the roots.  The Fungi have nutrients that the trees need, like nitrogen, phosphorus, potassium and other micronutrients.

Those tricky tree roots actually lure the fungus by secreting a sugar rich syrup like perfume that attracts the fungus.  “Come and get me fungus!”  The fungus falls head over heals for the tree root and penetrates and infects the root cells.  Then the fungus wraps its arms, called fungal hyphae, all around the root.  The two actually begin to grow together so closely that you can’t tell where the tree root begins and the fungal hyphae end.  That’s why we call it mycorrhizae.  mykos=fungus  riza=roots.  Literally fungus-roots. Naturally, when Arborsmith fertilizes your trees we use beneficial Mycorrhizal fungi.

The tree allows the fungus to have some of its sugar in exchange for nitrogen, phosphorus and potassium which are essential to tree growth.  Another benefit of the association is that the fungal hyphae greatly extend the surface area of the root, making it much more effective at harvesting nutrients and water.  The root is so pleased with this new source of minerals that it doesn’t need to grow as long, allowing the fungus to branch out and harvest for it.  That smart tree root has given up just a little sugar, gained the nutrients it needed, got access to more water and saved energy in the exchange by not having to extend itself out so far.

Not far under the snow there are also a whole host of soil microbes, bacteria, virus, fungus, wiggly worms, and bugs that you can’t see that are digesting the leaves and twigs on the forest floor, living, dying and creating food for the spring growth spurt.   Things are never as quiet as you might think under the snow in your back yard.  

In February the sap begins to rise and guess what that means?

Stay tuned for Maple sugaring time. 

How do you tell if a tree or shrub branch is alive or dead in the snow and cold of winter?

Mother Nature's Moment

by Lesley Bruce Smith ISA Certified Arborist

Wintering Beech Tree by: Lesley Bruce SmithThis is a question we are so often asked this time of year. It is really quite easy and I have created a very short (less than two minute) video explaining the secret on how we tell the living from the dead.  It is all about little observations that most folks overlook and understanding how trees grow...easy peasy!

Click here to find out how!