When in its native environment the ash is host to over 100 of insects, which is one reason the tree is considered magical and is the model of the iconic tree of life imagery. Not all of the insects the European ash plays host to are beneficial. Like most members of the genus Fraxinus, in most of North America the European ash is ravaged by the Emerald ash borer. If you live in the narrow hardiness range that the European ash thrives in, and are up to a gardening challenge, maintaining this giant in your landscape might be exactly the mythic quest that you’ve been looking for. Keeping the European ash tree pest free is impossible without being proactive because of the Emerald ash borer. It is not a matter of if your tree gets infested. It is a matter of when.
Soil
Luckily soil is not an issue with the European ash. It is relatively adaptable and can handle a variety of soil conditions.
Water
Water the European ash two to three inches when young. Regular watering is not needed when the tree matures unless there is a dry season or especially dry weather.
Temperature and Humidity
The European ash is native to the cool somewhat damp climates of northern and central Europe. It does not react well to changes away from this temperature range. In North America, the tree has done well in British Columbia and the Pacific Northwest.
Pruning
Pruning is synonymous with ash trees. The European Ash can grow 12 to 18 inches a year. During the second or third winter, after the leaves fall, you will want to do your first pruning to establish a central leader, or singular trunk, and prune out any crossing branches. Always use sharp tools that are sterilized with alcohol to avoid spreading disease. While pruning be sure to look for dead or dying branches and remove them, taking note if there seems to be an excessive amount, this which can signal a more serious issue. Always remember, with Ash tree waste to check if you are under quarantine before you dispose of anything you prune. You can call your local DEP or extension agency for clarification.
Emerald Ash Borer
The biggest concern for all trees in the genus Fraxinus since 2002 is the Emerald Ash Borer. The insect has caused the deaths of over 17 million trees at a cost of 10.7 billion dollars. In areas where the EAB has spread, your tree will eventually be infested. If you are cautious and keep ahead of an infestation and treat your tree before damage is too severe, you may be able to save or prolong the life of the tree. Look for the common symptoms of an infestation which are: canopy thinning and crown dieback, random leafy growth from stress, woodpecker damage, D- shaped exit holes, S- shaped galleries or grooves, and splitting bark. When all these are present it is time to consider treating your ash tree. A good indicator of whether the tree can be saved is if one third of the tree is damaged, Then, it is a better idea to remove the tree for safety and cost reasons. If the tree is not yet that to that point of damage, and it is smaller than 20 inches in diameter, you can treat it yourself with pesticides. If it is larger than that, or if you are in doubt, hire an arborist who is a licensed applicator.
Diseases Other Than Emerald Ash Borer
The most serious disease you need to contend with is Ash Dieback. Ash Yellows, which is caused by a virus that damages the trees vascular system. Experts believe the cause of the virus is insects but do not know much more than that. The symptoms to look for are slow twig growth and rapid die back. Leaves on infected trees are frequently smaller, thinner and lighter green than usual, branches might produce tufts of leaves called a witches’ broom. There is no cure for Ash Yellows so the treatment is the removal of the tree to avoid further spread.
Cultivars
If looking to plant a European ash cultivars are much more desirable than the common form and also more available in the nursery trade. Some examples are:
Fraxinus excelsior ‘Aurea Pendula’
Weeping form of the European ash with striking gold stems and golden foliage as autumn progress. A tree that promises all season interest.
Fraxinus excelsior ‘Pendula’
A slow-growing tree with branches that are pendulous giving it a nice weeping look. It can attain a height of 15-20 feet.
Fraxinus excelsior ‘Aureafolia’
An Amazing specimen tree with yellow bark that starts the season bright green then shifts to a golden hue around July.
