Hi, just seeking advice about growing grisliinia littoralis over new pvc drains, and near septic and water tanks. We have these planted as a hedge and have been growing for year and half so still young plants. We had a visitor who was a landscape gardener who was adamant that we should not be growing them over our house drain pipes that pass under these plants on way to septic tank. He said that the roots are very invasive and will seek out any water source and cause damage to the pipes, and septic tank. He suggested we transplant them else where and pant some thing else to screen the water tanks and septic unit. Eg. Golden totara or a pittosporum! I don't particularly want to dig them out, is he right?
A plumber/drain layer I spoke to didn't think there was a problem as pipe are pvc, and roots would only cause damage if a joint failed and roots could penetrate. This could happen with any tree. Any yes more likely with old clay pipes. So now I'm confused as to what to do. My partner wants to take them out just to be safe. I can't find any negative issues with grislinia roots in any online info. Has anyone had any experience or knowledge on this?
If the drain pipe is perforated, as some drainage pipe is, then you will be in trouble sooner or later. If the drainage pipe is not perforated then you will probably be fine until you poke a fork through the pipe without realising it.
I would transplant the griselinias just in case.( I moved a Griselinia two weeks ago which was over a meter tall, because it was where a fence post was going in, and it suffered no ill effects, didn’t even droop in the height of a hot summer, but ideally I’d leave that job till autumn after it’s rained.)
The main reason being if somehow you end up with a smashed or broken PVC pipe you would need to access it easily and you wouldn’t want any sizeable plant spreading their roots into it either.
We have a similar setup with water and septic tanks and pipes everywhere but with fences recently added and why I need to be careful with planting around the area.
Griselinias marked with a cross.
Septic tank -blue dotted line from house
Water tanks -yellow dotted line from house
My problem started (and I am going off at tangent) when we got impatient and I planted some shrubs to obscure the pump shed from view as you drive to the house.I didn’t even get my lines right in relation to future fences and will be transplanting all the plants shown! We should have waited till after we had the fences in place, necessary to keep stock away from water tanks, septic tank and pump shed, but fencers were also in demand and we had to make do with electric fences. And before any fencing or planting was done we should have located and marked the stormwater and sewage pipes from the house to the rainwater and septic tanks respectively, instead of relying on memory a year later to dodge them and to determine where the fence should go.
Even though we tried to go off a drainage plan to locate the various pipes, some weren’t quite where they were supposed to be. We found this out when we had the fencing guys come round with a post rammer to put some fence posts in. Luckily they chose to hand dig a few of the crucial post holes and found that they were perilously close to and narrowly missed a couple of pipes by inches!
They were very careful but they still could’ve hit some other pipes, in which case we won’t really know until our rain tanks don’t fill or wet patches appear where they shouldn’t. Droughts are good for showing up such wet patches and in my case I will leave the lawn brown and take the plants out in the meantime and then take time to choose suitable plants and decide where to plant them all over again.
Thanks for your reply. Will you replace the griselina with another type of hedging screen? Just wondering if it's a problem with them, or I shouldn't be planting anything to screen my tanks/septic other than light weight shrubs. Though I might talk to a few nurseries to get their take on it, or make some planting suggestions.
To be honest, I wouldnt.
Grisselinia are large trees, 5m or so in the north island so a tree of that size will have a considerable root system. While I doubt they will penetrate the pipes, they could crack them with their root network as I assume the pipes are not that deep underground.
If something happens and you need to access the pipes, that would be very difficult.
If you were to shift them, I would cut them in half to reduce transplant shock and not do it mid summer. They might look ok after transplanting and they do transplant well, but best not done at this time of the year
Thanks everyone for your responses. We have decided to transplant the griselina else where (autumn prep for a winter move). As you have all concluded, and a Nursery Centre agreed , these are big trees. In fact any tree over your drainage pipes is a possibility for trouble so don't chance it.