Answer: It's natural for Queen Palms to lose their lower leaves so I think your plants are behaving as they should. Sounds to me as though they're getting adequate food and water, inspite of the lava rock. Since lava rock is light and porous, I don't think having it under the trees will affect them in any way. You might want to check to make sure the rock wasn't placed over plastic (a common practice to keep weeds down). If there's plastic sheeting under the rock, it will definitely keep moisture from penetrating the soil and will keep air from the soil surface. If there's plastic under the lava rock, I'd remove and replace it with a poly-spun fabric weed barrier and then put the decorative rocks back.
Q&A Library Searching Tips