I get where you’re coming from, but I actually think plant choice can matter more than it seems—at least in the long run. You said,
Thing is, I’ve seen a few roofs where someone swapped out sedum for “just a little” native grass, and a couple years later, the roots found their way into seams or started holding more water than expected. Even with good drainage, some of those grasses can get sneaky. I’m all for flexibility, but sometimes those picky adjusters are just trying to head off headaches down the road.“as long as you’re not overloading the structure or blocking drainage, plant choice seems pretty far down the list of concerns.”
I get where you’re coming from, but I actually think plant choice can matter more than it seems—at least in the long run. You said, Thing is, I’ve seen a few roofs where someone swapped out ...
That’s a fair point about roots getting into seams. I’ve seen sedum work fine, but once someone put in a patch of wild rye and it started causing drainage headaches within a year. I get why adjusters are cautious—sometimes those little changes snowball.
Interesting you mention wild rye—I've seen similar issues with grasses that have deeper roots. Sedum seems to stay pretty shallow, but once someone tried adding some native bunchgrass to a green roof I managed, and it started poking through the membrane in spots. That led to leaks we didn't catch until the next big rain.
Do you think there's a good way to balance wanting more diverse plantings with keeping things low-maintenance? I get why people want to experiment, but sometimes it feels like the risk outweighs the benefit, especially if you’re dealing with warranties or insurance. Have you ever had luck convincing owners or tenants to stick with the original planting plan, or do folks usually want to try something new?
I’m also curious if anyone’s found a workaround for drainage issues when someone insists on swapping out plants. Is it just a matter of better root barriers, or is it more about regular inspections?
I’ve run into this exact thing—people want to “spice up” the green roof, but then you get those deep-rooted grasses and suddenly you’re patching leaks.
Couldn’t agree more. I tried to talk my partner out of adding prairie dropseed to our roof garden, but they were set on it. Ended up with roots in the drainage layer and a mess to fix. Honestly, I think regular inspections help, but nothing beats sticking with what works. Root barriers only go so far if someone’s determined to push the limits.“sometimes it feels like the risk outweighs the benefit, especially if you’re dealing with warranties or insurance.”
Funny, I actually had the opposite experience—added some native grasses (not dropseed, but similar) and didn’t run into any root issues, at least not in the first few years. Maybe it depends on the roof build-up or climate? I’m in a pretty dry area, so maybe that helps. I do wonder if folks sometimes underestimate how much the substrate depth and drainage design matter, rather than just the plants themselves. Anyone else have luck with “riskier” species?
