I have heard of foliar feeding but I have not seen it often. I know the leaves react when chems are sprayed on them and have to dry before going back in the sun. With these trees keeping a reservoir of water in the caudex I would guess that is why they are also root fed. So I don't remember if foliar feeding worked or not.

African Violet fertlizer is okay. Any ferlizer when used on leaves I suggest trying 1/8 to 1/4 strength. Yes spray early in day. Do not spray on days it can't dry by evening. Spray extra some days and tip the crown down in for instance Phalenopsis so salts don't buildup. Idea is to flush the crown to not burn new leaves generating there. Avoid High Salt fertilizers like Miracle Gro solid forms so salt doesn't build up faster than normal. All non arid climate tropical plants have stomata and can likely take in foliar feeds. Yes both leave sides have stomata openings for gas exchange and with mositure uptake potential. Yes the highest density is typically underneath. Orchids often close stomata, at least partially, when at low light. And they need to fertilzer nutrients when light is present to metabolize and grow well. So best guess is AM, as the sun is coming up before you go to work, is a best compromize time to foliar feed.

I use the fish emulation the one i use doesn't have a NPK so i can use it evey watering i allso use it after I repot any of my plants it supposed to relieve stress due to repoting imo it helps. As for what mr ko uses i don't know. I must tell u use half strength if u keep using any foliar sprays on seedlings they dont really need fertilizer:×)

wondering how people fertilize ... I’ve been foliar feeding my veggies with kelp, but will the hippie leaves absorb the spray? Would love to hear about fertilizing advice. TIA, Genez