Will mycorrhizal fungi cause plumbing damage?

I've been offered the choice of a free sachet of MycoGold Mycorrhizal fungi, or a Seville orange tree through my garden club.

I read up on th product and it says tree and plant roots will grow up to 1,000% longer which is great for their health. The problem is that I'm in a high density urban area where tree and plant roots reach neighbour's' plumbing which needs thousands of dollars to fix.

Anyone know about this sort of product? Should I just get the orange tree and plant it in the street (since I have no room for one because I don't like bitter oranges).

To answer the question of the subject, no, mycorrhizae will not damage plumbing. It really depends on the tree. Certain trees are more apt to cause damage to buried pipes than others. Trees can be categorized as either having invasive roots or not. Some examples of trees with invasive roots are cottonwood, willow, and some maples among others. These roots tend to stay shallow and spread out in the soil instead of going deep. Roots from these trees can bust pipes, house foundations, sidewalks, etc. An example of a tree that does not have invasive roots are oaks. Oak trees have a tap root, and the rest of their roots like to go down and deep, rather than shallow and out. With the aforementioned in mind, any tree can have "invasive roots" if planted right next to a house or over top of/too close to buried pipes.

I read up on th product and it says tree and plant roots will grow up to 1,000% longer

I tend to doubt the guarantee that the label claims they will grow 1000% more. I'm more apt to believe they can grow 1000% longer, in the right conditions. I haven't read the label myself, but I tend to think that this percentage increase may be more likely to do with the fungal hyphae thread of the mycorrhizae reaching out from the root into the soil that can increase the percentage of a roots ability to reach nutrients and water many times more than just a root itself.

All trees have roots that can invade plumbing pipes.
Water lovers are the  worst offenders.
Even tap root trees will have their feeder roots near enough to the surface to do damage, especially oak trees. (Look at streets and sidewalks in Southern Cities for proof of how destructive the roots of an oak can be)

There are ways to keep roots out of the plumbing though.
If you know where the pipes are, you can install diverters made of steel or aluminum to encourage the roots to turn away from the pipes, you can keep the soil moist so the trees roots don't seek water that is in the pipes, you can use a long bladed spade to cut the roots (has to be done at least once a year).

I would choose the mycorrhizae myself, there are many uses for it both for trees and for vegetable gardens.
These fungi attach to the roots of plants and help them grow by both providing nutrients and acting as protection from root eating nematodes and other nasty microorganisms.

Redhawk

(Tree roots, other than the anchor roots, will tend to stay within the top 24 inches of the soil, this is where it is easier to find oxygen and water along with the microorganisms that provide the nutrients the trees require.)

Will the mycorrhizal fungi hurt your pipes?  No.  The impossibly thin strands of mycelium have no structural strength to speak of.  They are easily broken and swept away.  They are really no larger and stronger than strands of cotton candy.  A healthy fungal network has thousands of miles of these thread-like extensions.  

The tree roots will, however, be stronger and the entire tree more robust as a result of the fungal network.  Ultimately, that is what will invade available water sources (pipes).

Will mycorrhizal fungal increase root growth by 1000%?  No -- that's hard to imagine.  But the fungal network will dramatically increase the soil to root contact exponentially -- far in excess of 1000%.  Basically, the mycelium extends the range of the roots by helping the roots capture nutrients.  

Whether you innoculate your tree with fungi or not, a fungal spore will eventually fall to the soil near your tree and a fungal network will be established (if it wasn't already there when you first planted the tree).  Fungi happens.  And that's a very good thing.

Marco Banks wrote: The impossibly thin strands of mycelium have no structural strength to speak of.  They are easily broken and swept away.  They are really no larger and stronger than strands of cotton candy.  A healthy fungal network has thousands of miles of these thread-like extensions.  

Will mycorrhizal fungal increase root growth by 1000%?  No -- that's hard to imagine.  But the fungal network will dramatically increase the soil to root contact exponentially -- far in excess of 1000%.  Basically, the mycelium extends the range of the roots by helping the roots capture nutrients.  

Mycelium are highly structured and they are strong enough to entangle and hold parasitic nematodes and even some beetles. Not exactly weaklings.  Mycelium tend to grow similarly to climbing bean plants, the strands will intertwine with each other, creating a hyphae rope type structure.
Several studies have shown that root length and density can be as much as 20 times longer and thicker than plants that grew without any mycorrhizae (that is more than 1 thousand percent).
Mycorrhizae can be either external of the root or internal, the endomycorrhizae actually invade the cell structures of the roots so that nutrients are delivered inside the root, eliminating the need for the root to suck the nutrients inside before transporting them up to the leaves.
Exomycorrhizae wrap around the outside of the root, creating a sort of envelope that protects the root from any attacks, it is this form of mycorrhizae that wraps up the bad organisms, such as root eating nematodes and then the fungi devours the intruder, releasing any nutrients it didn't need for its own survival.
The hyphae network consist of many different species of fungi, most of which have a symbiotic relationship with not only each other but also the plant roots they come in contact with.  
The fungal network works like a super highway (freeway system) for bacteria and other microorganisms who use the hyphae strands to travel along. These super highways also act like electrical grid power lines, passing along electrical signals from one plant root system to another, these signals can travel great distances (many, many miles).

Redhawk