Green Algae in Orchid Bark and Moss: Florida Humidity, Moss Removal, and Physan Treatment

Question:

Orchids (especially Phals) showed underwatering signs (crinkly leaves, dry dying roots). Increased watering; now green algae in bark/moss. Safe or overdone? Water weekly, soak+drain. Florida greenhouse (fans/vents)—hot days: mid-week water if bone dry. Plants look better, but algae?

Answer:

Hello Theresa,

Florida humidity → algae on moss. Remove moss, use only bark. Algae probably harmless but unsightly.

Rising temps + good ventilation → increase watering. Weekly good for cool weather; 2–3+×/week above 90°F.

Some use Physan (algaecide) for algae—go easy, dilute per instructions (strong doses harm roots).

Jim Kawasaki
San Jose, CA