Answer: I think you're right in being concerned about excess moisture next to your foundation. It isn't a good idea to plant too closely to the foundation, both for moisture related problems and because some roots can compromise the concrete. Most landscapers suggest keeping plants 3-5' away from the foundation. You should be able to plant low-water use plants close to the house, but you'd be taking a chance by putting water-lovers there. I would incorporate a slope (by raising the bed) to help facilitate drainage. You might also consider installing a curtain drain close to the foundation. A simplistic overview is to dig a trench, line it with gravel, set a PVC pipe with perforations all around and cover it with more gravel. This will give excess water a place to go, but you'll need to direct it away from the foundation so the excess water can drain.
You may also be able to cut down on the amount of water required by the plants if you amend the soil with organic matter. Compost (or aged-manure) mixed into the soil will help it drain quickly, but will also help hold just enough moisture to keep the plant roots happy. This should result in healthier plants with less water usage.
Hope these suggestions are helpful.
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