Algae on growing medium

[LiveLaughGrowOrchids]

Hello all, I repotted a Phal orchid for my mom yesterday(she was worried she would kill it) and found that all around on the outside the sphagnum moss was emerald green with algae. I removed most of the old media, but a lot of the healthy green roots were also this dark green color.

It was growing in a see through container and seemed otherwise happy, was flowering until recently, for about 5 months.

Is this harmful to the plant? Should I have removed all those roots?

I've repotted it in a mixture of moss and bark.

Thanks!

[Brooke]

Algae isn't a problem in Phals. You never remove firm roots, regardless of the color. It sounds like you did everything correct.

Brooke

[RosieC]

[tucker85]

With moisture and fertilizer in the potting mix, algae will eventually grow, especially in a clear pot that lets in light. That's one of the reasons that it's recommended to repot moisture loving orchids, like phals and paphs, once a year. Some books recommend using Physan 20 once a month on phals but I don't like to use chemicals unless I really need to. The algae won't hurt the orchid.

[Dante1709]

I personally like hydrogen peroxide for algae.. I used to have algae in my rainwater, and after placing a bit of hydrogen peroxide and waiting, the water wasn't green anymore (although it was cloudy because of dead algae)

Hydrogen peroxide shouldn't be harmful to the plant ; it converts back into oxygen and water. It can help aerate the roots. Just use it sparingly, just in a case