What kind of stone is better to use on top of orchids?

Topdressing the surface of an orchid pot is a technical job in itself. Topdressing is not simply decorating the loose soil on the pot surface; it involves many key factors related to orchid growth. Many people just simply lay moss on top. Laying moss carries risks. I suggest laying moss in autumn and winter, and removing the moss promptly during the plum rain season and summer. In spring it retains too much moisture, causing root rot. In summer it insulates too much heat, smothering the roots and causing root rot. So what is good to use for topdressing an orchid pot surface:

For the material used to topdress an orchid pot surface, I suggest using breathable, lightweight materials, such as volcanic rock, expanded clay pellets and other granular types; those with air pores are the best materials. The material laid on top can be processed beforehand, and later it can affect the orchid's growth. Let me explain the method.

Volcanic rock, expanded clay pellets and the like have air pores. Their ability to adsorb nutrients is quite strong. Before laying them on the orchid pot surface, I soak the expanded clay pellets, volcanic rock and so on in a nutrient solution containing nitrogen, phosphorus and potassium elements. Soak for 3 to 5 days. Then scoop them out and let them dry. Then lay them on the surface of the pot.

Orchid roots do not absorb nutrients very heavily. The main way to supplement nutrients is with long-acting slow-release fertilizer, and the fertilizer effect must also be mild. Volcanic rock, expanded clay pellets and similar materials soaked through with nutrient solution have adsorbed enough nutrients, and then when watering, they slowly release trace amounts of nutrients over a long period. This way of supplementing nutrients is the mildest.

Summary: For topdressing an orchid pot, I think everyone can refer to my method, using porous, lightweight stones, soaking them in nutrient solution before use. It is all benefit and no harm to the orchid's growth.