I’ve seen the same thing with copper strips, especially on older roofs or spots that just never see the sun. Around here (Gulf Coast), it’s a losing battle with all the shade and humidity. The copper helps a little on the south side, but my north-facing slope still gets those black streaks every year.
Bleach and a pump sprayer is pretty much my go-to too. I just do it on a cloudy day to avoid any quick drying or damage, and rinse it down after about 20 minutes. It’s not fancy, but it keeps things looking decent between bigger clean-ups. I’ve tried some of those “no-rinse” roof cleaners too—honestly didn’t see much difference compared to bleach.
Only thing I’d add is be careful around the gutters and plants below. That runoff can be rough on landscaping if you’re not watching where it drains. Other than that, seems like we’re all just trying to slow down the algae, not stop it for good...
I get the appeal of bleach for a quick fix, but I’ve actually had better luck with sodium percarbonate-based cleaners. They’re less harsh on plants and gutters, and I don’t have to worry as much about runoff killing my azaleas. The downside is they take a bit longer to work, and you might need a second application on stubborn spots. Still, for anyone with a lot of landscaping right up against the house, it’s worth considering. Bleach just always made me nervous after I lost a few shrubs...
I get where you’re coming from with the plant worries—bleach makes me nervous too, especially since my gutters drain right into my flower beds. But honestly, I tried one of those “eco-friendly” cleaners last spring and still had green streaks after two rounds. Maybe I didn’t mix it strong enough? Bleach worked faster for me, but I just made sure to hose everything down like crazy afterwards. Not ideal, but sometimes I just want it done before the next rain rolls in.
Bleach worked faster for me, but I just made sure to hose everything down like crazy afterwards. Not ideal, but sometimes I just want it done before the next rain rolls in.
I get the appeal of bleach—nothing seems to nuke that green stuff quite as fast. But I’ve always been a little hesitant, especially after seeing what it did to my neighbor’s hydrangeas a few years back. Even with a good rinse, some runoff is almost impossible to avoid when your gutters dump right into the beds.
I tried a copper sulfate solution last year (just followed the label and kept it off the plants) and it wasn’t instant, but within a week or two the algae was gone and didn’t come back all season. The bonus is you can get those zinc or copper strips installed along the ridge line, and then every time it rains, they help keep things clean without any extra work. It’s not as quick as bleach, but I’d rather wait a bit than risk torching my perennials again.
Mixing strength might be part of it too—some of those eco cleaners are pretty weak by default. If you go that route again, maybe double-check the ratio? Just my two cents from getting burned (literally) on shortcuts before...
The bonus is you can get those zinc or copper strips installed along the ridge line, and then every time it rains, they help keep things clean without any extra work.
Those strips are a game changer. I put copper up on my last house and barely had to touch the roof after that. Bleach just feels like a shortcut with too many risks—my wife still brings up the time I fried her hostas. The only downside to the metal strips is the upfront cost, but honestly, not having to drag out the ladder every spring is worth it for me. If you’re in a spot that gets a lot of shade, they make a noticeable difference.
