i wonder if you might want to try what i did. i, too, had a troublesome area. a large area in front of my house retains way too much water because my house is lower than the street. what i did was to build four bottomless "boxes" (48 inches square, using 10-inch-wide boards). i added good-quality soil and soil conditioner and then planted hydrangeas and azaleas. they're thriving because they're raised just high enough to not be affected by the low-quality soil and flooding problems underneath. acting in accordance with some gardening advice i had gotten from books, i planted the shrubs 1/3 above the soil and mounded more soil around the raised roots.

pat
durham NC

Pat - Thanks for the reply.

That's kind of what I had in mind as well, though it didn't occur to me to use wood to make boxes...I was wondering how feasible it would be to bury pots way under the soil to slow down some of the water loss as it flowed down...same principal as what you described though.

You said you filled the hole with clay.. what type of soil was there to begin with?

Clay on top of gravel on top of clay builds more of a case for over-watering than under, especially since that area gets shade during the hottest time of the day. The first few inches of disturbed soil is going to dry out quicker. What matters is what the conditions are at the root level. And since a plant can show the same symptoms from over-watering as under-watering, it is hard to tell which it is without spot checking down below the first few inches of soil.

That is just my first impression based on the information given.

The area gets significantly dry in a short period of time, it's easy to tell. The previous plants were definitely not getting too much water.

When I said I filled the hole with clay, I meant that I replaced what gravel I could get out with clay. It's not slowing down the wicking effect though. There is such a mound of gravel at the sub-soil level, that it is draining every bit of moisture from the upper levels in short order. It doesn't help that there are 2 full-grown trees in this planting bed too and I know they are getting every bit of moisture that is made available to them, though their root systems are down at the original soil level before the gravel was apparently piled up.

Sounds like a great well drained area for herbs ....

Yeah, herbs is a good suggestion but I was hoping to find a way to make this work for an azalea. They supposedly like well-drained soil too...but this is *too* well drained.

If it's shady enough for azaleas, it would be too shady for herbs. The ones that like dry want full baking sun, in general.

To give a better idea of the location:

It's in a bed with 2 full sized trees on the corner of my yard in front of a fence that faces full east.

So it gets morning sun and by mid day, the trees and fence begin shading the area. Should be ideal for azaleas, but the dry soil conditions complicate things alot.

Don't you just hate when builders do that?? It's actually a very common problem for lots of people. I'd do the raised planter bed as suggested. It would look great and the plants have what they need.

Maybe build up berms of rich fluffy soil to act like a wet sponge on top of the gravel bed. Most people report better success building UP rather than digging down and trying to improve whats there. Your mound needs to be really fiber-y fluffly soil, not just garden soil piled up, you want it to hold onto water for a long time. But you will have to re-apply organic-y mulch-y topsoil every couple of years because it will settle quite a bit each year. I have seen berms as high as 4 feet, they will support shrubs but not tall trees (they tend to fall over).

Any suggestions on making the raised bed?

I guess I could go full-bore on this and do a raised bed made out of non-treated wood with a wood but well-drained bottom.

Or I could find some other way to slow the water drain below the soil level. What about 3-4 large planting pots buried down beneath? They would have draining holes so that water doesn't actually collect but I would imagine they would slow the water drain down some too.

Yes, you have an unusual planting situation. Creating a raised bed or berm over tree roots which tend to grow just under the soil surface will, in time, kill the trees. Not a recommended practice in the horticultural world. Azaleas are shallow rooted shrubs which probably are not suitable for this situation.

Based on experience I suggest the following approach. Lay flat, natural stone (the type used for walkways and dry walls) randomly about the space. Now, do a search for perennials suitable for dry growing areas. Many are evergreen. Many blossom or provide interesting texture. These are planted sideways in the ground with the roots under a flat stone. Mulch all heavily, even over the flat stones if you wish. The plants will quickly resume growing upright and become established, spreading and colonizing surviving on the moisture which collects beneath the rocks. With careful plant selection you will soon have an interesting garden. Two plants to try, among others, are Christmas fern and Santolina.

That's interesting. So there will be more moisture under the rocks even though those same rocks will prevent moisture from rain/sprinklers from getting to that same area?

I'm assuming that the rocks will serve as kind of a heavy-duty "super" mulch in that case...