The angle, close to a small cliff, can make gravity drain the water more than you would like it to and act as if you had sandy soil, where people have to water 50% more. I am not sure if this would help compensate fully but you could try water absorbing polymers and other materials. An organic minded store once recommended shale rocks that absorb and later release water (or at least I think it was shale rocks). I can call them to confirm if you are interested so you can locate a source closer to your home.

Keep them well mulched, maybe even past the drip line. and do watch out for competition from other plants as that certainly could also force you to water more often.

I wish I could think of a way to know for sure where all the water is ending up. Are any of the competing plants shallow rooted?

Do you have a little mound of soil on the down side of the plant to hold the water in long enough for it to absorb into the soil?

Hi luis and madeyna,

Thank you so much for your input. I think that I will look into the water absorbing polymers. luis, I don't think that the other competing trees have a shallow root system. I will certainly mulch it well though - so far I have got lots of wood chips over the area but perhaps I really need much more organic matters that will decompose there. madeyna, I will create that little mound of soil on the side too! :-)

Thanks again for your help!

Just a thought... I've had several trees removed and the stumps ground... while the "sawdust" is decomposing it sucks all the nitrogen out of the soil.... so maybe it's puny because it needs a bit of fertilizer? I usually wait a year before planting anything in the same space... even after turning in peat, compost, new soil, etc... I just give it some time to break down... then it is FABULOUS soil!