Here are a few of my inspiration photos

af366a19047a8a89033b4916a18cf121.jpg (563×778) · More Info

Landscaping with ornamental grass · More Info

Landscaping with ornamental grass · More Info

how deep is the top of the box? .. in other words.. how much soil will you be working with ...

if shallow .. do you expect any heat buildup? .. that might impact plant suggestions???

ken

The lid is 2-2.5 feet down. I don’t expect any heat buildup. Previously there was grass and it grew just fine

I do not recommend planting these over the tank/boxes. Ornamental grasses can become monsters. Root systems of some of them are beastly. If any work needs to be done, you're going to have to dig them up -- may be easier said than done, depending on how established they will have become. Also, I'd be worried about potential damage from those really strong root systems -- might not actually do any damage at 2-2.5 feet down, but personally I wouldn't take the chance.

Instead, plant the ornamental grasses in the vicinity of the structures if you'd like to incorporate them somewhere -- even a few feet away from the edge of the structures would be preferable to on top of them. Over the tank/box, plant something like annuals that you know won't interfere with the structures in any way and are quickly and easily removed if needed. I have tall zinnias planted over my tank and zebra grass *behind* the edge of the tank lid, which is between the perennial sunflower in the front and the zebra grass:

The grasses are even larger this year -- they're monsters, and I have to get out there to divide them...I'm dreading that chore.

Thanks for the feedback. I’ll have to put something there. Maybe I just cover the whole area in monkey grass.

Following up to say that this ended up being a non-project because we decided to sell our house. Thanks again for the feedback!