I spoke with several pond building technicians and they basically claimed that irises and other marginals should not damage, with their roots, the 45 mil EPDM liner if the plants are planted directly into the pond into a gravel substrate. Is this so?

However, they said that there was a plant unfamiliar to me and cattails that might.


Do you think that the non-yellow flag varieties of iris would harm my 45 mil epdm liner. If i remove the yellow flag irises at the end of the fall each year from the gravel substrate, would that be soon enough to prevent it from harming the liner just an inch under its roots?

I've had plants in gravel over the liner and no holes yet that I know of. I do think that given a constricted area to grow in, plants like common cattail and yellow flag iris could potentially put a hole in some of the thinner pond liners out there. Other native irises probably aren't going to be a problem. Mine are pretty slow to grow compared to the yellow flag iris.

I've tried to pull up yellow flag iris out of gravel in my pond overflow. It's not possible! It really sticks in there! I suggest not using yellow flag iris or keeping it constrained in a pot. I have to repot mine, hopefully this weekend. It has grown from a 2 gallon pot in 3 years out to cover about 25 square feet! I kid you not! I'll have to take a saw and loppers into the pond to cut it apart so I can remove it in pieces. I hope it's not too rooted into the gravel under and around the pots.