Identifying Tree Roots that managed to get into a new sewer line

[John S]

I have a new sewer line placed in 2021 that was offset to the iron line under our office building. In the process of the new line being placed between the city main and our building, the iron pipe was vibrated when but with a saw. This affected a joint slightly 3 feet under the building and created a slight gap. There is only one plant or tree within 35 feet ( A tall queen palm) and a Giant Ficus Tree 3 feet in diameter 130 feet away.  The question is, which tree is invading our sewer line. We suspect the Queen Palm but need to positively identify the tree roots. What do you suggest to prove which tree is the culprit before working with the city for the tree's removal.    Your thoughts and expertise is appreciated. 

[JLM]

Probably the Queen palm…
 

I don’t know what ficus roots look like though, someone may be able to identify one way or another, but with the queen being that close it’s quite likely the queen.

[96720]

I say ficus their roots are super invasive I had one planted about 40’ from my pond and it destroyed the pond notice I said had!!! Those roots don’t look like palm roots to me!!!

[Silas_Sancona]

Also thinking Ficus, but pictures of that tree / how tall  and wide the canopy is, as well any others within 60ft of the effected pipe would help..

As mentioned above, Roots on Ficus can travel quite a distance in search of water, though 130ft would seem quite a distance unless that tree is huge.. 

[Looking Glass]

Likely the queen.  Even though palm roots are not super invasive or destructive, palms aren’t stupid.  Palm roots will invade pipes if there is a way in, and moisture is present. Here’s my neighbor’s Adonidia, crossing over underground below a walkway, and invading irrigation pipes here by the foundation.  
 

[Looking Glass]

I could make up a way to tell for sure, and if I was working my old college job, I could do it in an afternoon.   Take a separate sample of each tree to a lab, and a sample of the roots in question. They could run gel electrophoresis after extracting and amplifying some DNA from each, and tell you with great certainty what the match was.  Would make a nice little project for an advanced biochemistry undergrad.  Getting this done in the real world would probably be difficult.  But we used to do stuff similar to this all the time, I did the mustard plant variants, and my partner worked with Madagascar hissing cockroaches for research.   We would get sunburns on our faces staring at the UV lights all night   Doing stuff like this was what some of my classes in chemistry and biochemistry were back then.  You got a problem like this and had to figure it out.  

Some botanist in the biology department might be able to look at the roots under the microscope and tell you also, but what fun would that be.  

[SeanK]

8 hours ago, Looking Glass said:

Likely the queen.  Even though palm roots are not super invasive or destructive, palms aren’t stupid.  Palm roots will invade pipes if there is a way in, and moisture is present. Here’s my neighbor’s Adonidia, crossing over underground below a walkway, and invading irrigation pipes here by the foundation.  
 

Wow. Glad my house is not constructed on a slab.