Question
Is it a good or bad idea to put ornamental bark around the base of large potted houseplants like jasmine, lemon trees, scheflera, bottle brush and palms to help hold moisture in a dry climate? Thanks!

Answer
Hi Jan,
  Generally it is not a good idea to cover the top of the soil of a potted houseplant. It may help to keep the soil wet/moist, but that is not always a good thing.
Covering the soil with ornamental bark or stones(or anything else really) can greatly reduce or stop air-flow into the soil and keep the soil too wet/moist for too long. Most houseplants need the soil to dry out a bit between watering.
Problems can arise quickly in soil that stays too wet too long. It encourages mold to grow (even in dry climates) and will attract fungus gnats (Mold will also grow in the ornamental bark as well as the soil).
Constantly wet soil is the same as overwatering. Eventually the plant will develop root rot and/or stem rot.

It is best to just water plants when they need it, allowing the top 1-2 inches of soil to dry between watering. Then water just enough for a small amount of water to drain out of the drainage holes in the bottom of the pot.

If a plant suddenly starts to have an almost constant need for water (the soil gets very dry a lot quicker than it used to), check to see if the plant is rootbound. A constant need for water is one of the most common signs that a plant is rootbound.

I hope this helps. If you have any questions or need additional information please don't hesitate to ask.
     Thanks
       Tracy