Ash Tree Devasted Sewer Line

Q. My neighbor’s ash tree grew into their sewer lines and because of that expense, I cut down 

mine. My HOA says I must replace it with another tree. I am looking for something smaller with less invasive roots. Thinking about a Bird of Paradise, blue Chaste tree or a Bottle Brush? What do you think? My front yard faces West. 

Ash trees for the most part make a great shade tree. Some of the older varieties can get a bit too large for single-story homes. This one is placed just a little too far and on the wrong side of the house to give it much shade. This is not a desert adapted ash tree like the Arizona hash. These older ash trees, like Modesto, do extremely well planted in lawns.

A. There are two things to consider regarding your question; why the tree invaded the sewer line in the first place and reasons for selecting a replacement plant. Any of your choices would be fine to fill a space but ask yourself the purpose of this plant before making that decision.

We are having a problem with many ash trees, whether they are desert adapted like this Fan Tex or not. The problem is called ash decline and I have seen it here causing problems for ash trees since the 1980s. This ash decline is bad enough that I hesitate to recommending planting ash trees at all until this can be figured out.

            In our desert, I don’t particularly like the idea of selecting a plant just simply because it fills a space. Did this ash tree provide seasonal shade? On the west side of a home this can be quite important for comfort and reducing electric costs for the AC.

Fan Tex ash can also get borers that can cause it to decline as well.

            To improve comfort in a home and reduce energy costs, it is more important to shade the South and West walls of a building than it is the roof. The most “bang for your buck” in this regard comes from deciduous (those that drop their leaves in the winter) small trees or shrubs that don’t grow much taller than the building.

Ash tree roots can be quite invasive and they will go anywhere there is water and nutrients. Sewer lines sound like a smorgasbord for them!

            Smaller plants generally use less water than larger ones. Pick something that can handle the heat of a Western exposure, drops its leaves in the winter and doesn’t get much above fifteen feet tall if you live in a single-story residence, 30 feet tall for a two-story residence. Plant it a distance from the wall about half of its mature height.

Ash trees come as either male or female "flavors". The trees selected and favored for landscapes are the male trees because the females make seed that drop everywhere and can be quite messy.

            The second issue is invasion of sewer lines. This can happen with nearly any plant but some are, root-wise, more aggressive than others. But roots need an opening or break in the line for this to happen. If the line is completely sealed, roots will not enter it.

Notice the graft union at the base of the trunk where the desirable male tree was grafted onto less desirable ash roots. This keeps the trees "male" and true to their namesake such as 'Rio Grande', Fan Tex' and 'Modesto'.

            Breaks in a sewer line are more likely if a tree is growing close enough so their roots “crush” it. Crushing a sewer line because of enlarging roots causes an entry point for roots to grow. Once this entry point is made, nearly any tree or shrub becomes “invasive” and plug it.

And ash trees can have nice fall color from yellow to reds to purple, weather permitting.

            Use irrigation to direct the growth of roots in desert soils. People who don’t live in the desert can’t use it to their advantage. Locate irrigation emitters on the side of the tree or shrub away from the sewer line to wet the soil away from the sewer line.

            Keep the area around the foundation as dry as possible a distance of at least 3 feet. As added protection, you might consider a commercial “root barrier” installed between the plant and the sewer line.