Getting a phal to grow deeper roots

[NatalieS]

I've only been growing orchids for five or six years, but my oldest plants are phals. Two are in clear plastic pots, and one I repotted into clay and has been growing in clay for over three years. I can say for sure that my other two phals do not have aerial roots growing out of their pots like the one in clay does! The longest ones in the picture are over 30cm long - they just do not want to stay in the pot.