I planted willow beside my septic tank about 15 years ago. It now has huge roots which I'm told could damage the septic tank as the roots search for water. Is this inevitable and what can I do to remedy it?
Willow is a very strong and tenacous plant. I suppose it could damage a tank, depending on how strong it is. I would check with a horticulturist to see what you can do.
It can do severe damage to septic tank systems. The issue is more so with the drainage pipes leading from the septic tank rather than the septic tank itself. The drainage pipes are pourous, in that they have holes (yellow pipe with weep holes) that allow the overfill from the tank to dissapate into the ground after being processed by the septic tank. These pipes are laid in trenchs covered in drainage stone.
The willow tree roots will seek this and entangle the pipes that could potentially lead to blockages and ultimately issues.
Given what shane has said, I think you will have to remove them. Probably best to kill them off first. Check with a knowlegable horticulturalist for the best means. Willow can grow from off-shoots so you need to kill the entire plant. But you need to exercise extreme care with appropriate weedkiller, so make sure you get good professional advice.