How often do you plan to open up your tank to have it cleaned? Something that would probably work in shallow soil is creeping thyme. Mine is an oregano flavored thyme about 4" tall with a pink blossom. At our other house I had a white creeping thyme, maybe 1/2" tall that actually spread into a brick walkway. A taller perennial with grey foliage and white blossoms that might work is 'snow in summer' Cerastium tomentosum. It can be invasive.

Before you plant, I'd amend the soil so that whatever you put in has the best possible chance. We actually have rough field grass over ours (which is situated in our back field.) It's easy to cut the sod and just flip in up en mass when the tank needs pumping, and it seems to survive as well as the rest of the field, but I can't remember exactly how many inches of soil we have over our tank. Whatever plant you put there, it needs to be something that can either function like sod and be removed and put back in just one or a few pieces, or something that you don't mind having to replace every time the tank gets pumped. I would think that something like a juniper which is woody and prickly to handle would not be a good choice.

Do you have a photo of where it is in your yard? You might get more suggestions with that to get ideas flowing. For instance, is it somewhere you could develop a perennial bed and put a half-buried fake rock that you could plant around with tall perennials or fountain-shaped shrubs like forsythia nearby to spill over and largely hide it, and then remove the "rock" when pumping time arrived (preferably scheduled for a time of year when the perennials would have died back and a shrub could be tied back without damage)? Is it somewhere that hardscaping would be appropriate, whether it would be a piece of moveable yard ar*t, a birdbath or fountain, or a path, a patio, etc where you could put a large tile to be lifted when needed?

Another plant that could be placed directly over it in a flower bed (like the thyme suggestion) would be one of the low-growing sedums, but neither thyme or se*dum would be able to compete well with grass in a lawn setting.

I'm just curious as to why your septic tank is buried so shallow. Ours is about 3 feet down I think. Still I agree with others that ornate landscaping is not a great idea, given that the tank must be serviced periodically. We have lawn grass/pasture grass over ours and flip the sod over, then replace it, as nhbabs described.

I think you will have a very hard time growing anything in only a few inches of soil. Not just because of the lack of depth, but because of the heat. The soil won't be the same temperature as teh regular ground soil. Is there anyway to add more soil? A foot would be better.

My septic tank is right in front of my house under 4-6 inches of soil. I have a collections of pots and a birdbath over it. I imagine anything that would be ok in a rock garden would do ok over it, like low sedum and such. But the pots work for me. The jack-o-lantern (taken last halloween) is in the center of the tank.

Lisa

I think I'd just make a little "Welcome" paved seating area. It wouldn't have to be the shape of the tank. You could go a little beyond the tank so that it could be curved or whatever shape to look good. When the tank needs servicing you could just lift the pavers. A few choice plants along the back of the mini-patio, a nice bench and a well placed pot or two and I think it would enhance the entrance to the porch as well, since it's right between the two sets of stairs!

Cliff, my septic tank is in a pretty shady spot and is only covered by 4-5" of soil max. I planted over it. I lined up 3 Leucothoe along the edge so I knew we would always be sure to be able to locate it. On top of the tank I have planted bearded iris, sedum autumn joy, david phlox and miscanthus 'Huron Sunrise'. I usually fill in with some annuals like coleus as well. Surprisingly everything has been doing very well and blooming fine.

Just to be clear, when the tank needs to be pumped out the entire tank doesn't need to be uncovered, only the access area. It's maybe 18" across.