"Makes me wonder if certain plant choices could simplify things a bit—anyone tried low-maintenance groundcovers or something similar?"
Yeah, totally agree with this. My sister's green roof had the same weed problem at first, then she switched to sedums and thyme varieties...game changer. Hardly any weeds now, plus it smells pretty nice up there. Worth considering!
Sedums are definitely a solid choice—I've seen them thrive even in pretty harsh conditions. Another good option is creeping phlox; it spreads quickly, looks great when flowering, and does a decent job crowding out weeds. Just keep in mind that thyme and phlox might need occasional trimming to keep things tidy...nothing major though, just a quick once-over every now and then. Overall, groundcovers really do simplify maintenance compared to grasses or mixed plantings.
My folks actually put creeping phlox on their shed roof a couple years back. Looked amazing when it bloomed, but yeah, they had to trim it now and then or it'd start drooping over the edges. Still, way easier upkeep than grass or shrubs...
Creeping phlox is actually a pretty smart choice for shed roofs, especially if the slope isn't too steep. It helps with insulation and even protects the waterproofing layer underneath from UV damage. Definitely lower maintenance than grass—seen enough roofs where grass just turns into a soggy mess. A little trimming here and there sounds manageable, and it probably looks great when it's flowering. Good call by your folks.
"Definitely lower maintenance than grass—seen enough roofs where grass just turns into a soggy mess."
True, grass can get messy, but creeping phlox isn't totally foolproof either. Had it on my shed roof for a while and found it attracted bees like crazy during flowering season... something to keep in mind if you're allergic or sensitive.
