top dress with thin layer of 5/16 inch lava scoria. The red gravel will pop the lavender's foilage colar and it will not add that much weight, besides it will give off iron every time you water.

Just about anything you add to the top of the soil is going to result in a pain in the behind down the road. Is the moss a problem because of the difficulty in watering through the mat? Besides a thin layer of perlite, which is what I do, the only other thing I can recomend is not letting the top layer of soil stay moist. Growing lavender helps since it is pretty drought tolerant. I also just no worry about it and every once in a while I dig it out and replace the top of the soil in the container. I realize it is time consuming (not bad tho') I also force to look at each, and every plant, and evaluate how it is faring.

A number of commercial growers in this area topdress their containers with agricultural charcoal. It tends to be pretty lightweight, is a natural anti-pathogen and does a great job of retarding weed development as well.

I've killed liverwort(related to moss), cress, and other germinating weeds in winter coldframes by spraying undiluted food grade white vinegar on container surfaces. I try to avoid spraying foliage, but have not noticed damage where contact has occurred. These have been dormant cold-tolerant palms and other sturdy types. Every species is different and some would probably be burned by contact with the vinegar.