I have a rather small fungus gnats' infestation with my plants. While I am applying some other solutions, like neem oil, diluted hydrogen peroxide, etc. for my container clematises I would like to try a physical barrier in form of a 1-2cm (half an inch) layer of sand on top of the soil. I already did that with one zamioculcas and it seems to work, but while zamioculcas can be watered once every week or so, clematises require regular watering. Anyway, while researching clematis container growing resources I have not seen anyone putting a sand layer on top. Mulch - yes, sand no. Sand is also being mixed with soil.
Hence, my question to clematis experts - if I put top layer of sand in my clematis containers will it affect them in any bad way (increased wilt risk, etc.)?