why does your septic need to be in shade???

more facts so as to appreciate the situation.. or pix.. would help greatly ..

ken

In general, everything I know and have read says NOT to plant trees near a septic tank and leach field - shrubs and perennials usually can be planted with no problems, but aren't "shade plants". If the septic system is there, then I think you will have to either decide that the leach field may be damaged and need to be replaced down the road, and plant regardless - which can run into BIG bucks, and probably damage the tree roots to where they need replacing - or find another way to shade your house.

Window awnings are a traditional means of shading at least part of the house. You could also build a porch, which would shade at least the lower half. You could plant a pergola, plant it with vines, and let it shade the house - how much depends on height, width and style. You could put trellis on the side of the house - spacing it out about a foot, to allow for air space for circulation and cooling - and plant vines or train espalier trees on it.

Since you say this is the western exposure, and most of the heat from the sun will come from the Southwest, can you plant something more to the south that would be out of the leach field area and give enough shade to at least part of the house? Some oaks, and tulip trees, can grow pretty fast, given the right conditions. A male sweetgum is speedy-growing, also. And there is always something like a thornless honey locust, which will give lighter shade.

Many fast growers will also search widely for water, including into your septic system. Poplars are notorious.

Near my leach field, I use tall bamboos for screening/vertical accent (roots stay superficial), tall shrubs (Photinia, Ligustrum, tall cultivars of Euonymus japonica, Buddleja, Rhaphiolepis 'Majestic Beauty', Feijoa, etc. All can be pruned to become small trees.), and LOTS of fast growing trees (some are so-called "weed" trees) in large containers (hybrid poplar, Acer negundo, hybrid willows, Catalpa sp., Albizia julibrissen, etc.).

These fast growing trees are not adapted to pot culture, but they grow so fast, are so easy to propagate, can be pruned drastically, etc. etc., that I can just propagate more of them if they fail. I can continue to increase pot size, and/or root prune, if I choose to work that hard. This has been my answer to the 'instant' shade landscape, without the roots running amok in my septic system and water supply.

In my unheated greenhouse, since February, I have some Acer negundo saplings that have put on 3' of growth, Albizia 2', hybrid poplar 1', and we're still having late frosts!

What about extremely tall ornamental grasses?

While I wouldn't plant in the immediate vicinity of the septic tank itself, and I'd stay away from willows or maples in close proximity to any part of the leach field, there are many trees that would not pose a tremendous threat to your septic system - see the list in the linked article below.

Additionally, if you're concerned about root invasion, you can flush copper sulfate down your toilet once or twice a year, effectively killing any tree roots which may have made inroads into your field lines, without harming the overall system in any way.

Here is a link that might be useful: Planting on your septic drain field

Cedar Elm: Ulmus Crassifolia is native to the southeast. Resistant to dutch elm disease. It grows very upright. We planted a hedge of them along the west wall of our house when we first moved in. We've only got 5 feet of sideyard and they've done just fine. An extremely versitle tree!!

We also have Japanese Ligustrum mixed with the cedar elm. It's one tough very fast growing cookie!!! Both have done an excellent job of shading the west side of our home.

It's a pretty common misconception that if a tree is tall and narrow, it won't necessarily have a widely spreading root system. The root spread can be significant and is often quoted at 3 times the diameter of the canopy and as much as 4-7 times the diameter. But these references are usually made with respect to a typical spreading tree canopy. There is a very general correlation with the spread of a tree's root system to its height, so a very rough rule of thumb is to allow for a root spread equal to the mature height of the tree - eg., a 25' tall tree will have a root spread with an approximate 25' radius. It's a good idea to keep these rough estimates in mind when planting any tree near a septic field and locate appropriately. And moisture loving trees will often extend their roots much further to access a moist soil situation, like that which a septic field typically offers.

Also, I would never suggest planting ligustrum in the southeast, where it is considered an invasive species.

Instead of a tree, how about a pergola with vines?