The Green Ash, from the Olive Family Oleaceae, has been an extremely popular tree due to its adaptability to a variety of conditions and soil types, and because it is very fast growing. It is also highly drought tolerant and a native to North America. You can find Green Ash planted virtually throughout the entire United States in public parks, streetscapes, business landscaping and private homes.
Green ash has an average life span of 100 to 120 years and will reach an average height of 50 feet (up to 80 feet in the case of the Newport), spreading out to about 40 feet with glossy dark green foliage. The foliage turns yellow in the fall, but the color is sometimes unpredictable and often duller in the southern part of the U.S.
There are several different varieties of Green Ash and when you go to the nursery you may be confronted with a choice between two common types, the Newport and the Marshall’s Seedless. Although both are attractive and popular, there are significant differences between the two that you should be aware of before you take your tree home.
In general the Marshall’s Seedless variety has been found to be a weaker tree and is susceptible to storm damage. However, good pruning will always minimize this risk. Additionally, the Marshall’s Seedless is seedless in name only. Recently, females can be found in the population and produce a large quantity of seeds which can be a nuisance to clean up.
For this and other reasons, you may want to consider the Newport as a less fragile and more attractive tree. The Newport has been found to be a sturdier tree and has a red tinted bark and reliable bright yellow fall foliage.
With that in mind, both types can cause problems with their surface roots uplifting sidewalks and other landscaping. However, if you plant them in well-drained looser soil, this will minimize problems. Placing root barriers around the periphery of the planting area helps move the roots down. This technique should also help the roots to be deep and that way you’ll have less maintenance worries.
Green Ashes in general require regular pruning, especially when young in order to develop a strong central trunk. Multiple leaders may develop from improper pruning and this weakens the tree. At the nursery, look out for trees that have been topped and have a more bushy appearance. These trees are weaker and won’t hold up well in a big storm. In the case of the Newport, topping will weaken an otherwise strong tree. At the nursery you need to look for a strong central leader and make sure that the branches of your tree are evenly spaced. If you find two big branches that are opposite each other, you can cut one to create a stronger tree.
As far as planting goes, both varieties are easy to transplant from the nursery or containers. They grow well in urban areas with salty, high pH, and compacted soils, but are not recommended for dense clays. Plant your tree in full sun.
Green Ash is susceptible to several types of pests and diseases, but keeping your tree healthy and free of pests and diseases is fairly easy. Here are some tips that apply to both types of trees.
Regular fertilizing is important, and if your tree seems to be disease prone a high nitrogen fertilizer may help. It’s also important to water more during drier periods. If you find that aphids have settled on your tree, not to worry as these are not considered a major threat to the health of the tree. Another concern is fall webworms that can nest and eat up the foliage. Prune the branches low to the ground where the nests appear as soon as you spot them. It’s also a good idea to also rake and dispose of fallen leaves that in any way look diseased.
With these basic ideas in mind, you should be enjoying a nice and healthy shade tree in no time!
Here are a few helpful sites with more information about the Green Ash:
Green Ash (Fraxinus pennsylvanica)S.D. Department of Agriculture