Is there enough volume in your planters? Or is it that the brick drinks up all the water?
If it is wicking, you could line it with plastic (or varnish the inside), and try some of the gel water absorber you can get from Stokes or other vendors.

If you don't have the volume and it will dry out anyway, you need to try something that loves to be dry. Portulaca is a nice hanging plant - but it is not as trailing as the potato vines.

You might try a small watering drip tube that leads to a hidden water source.

Hope this helps.

Here is a link that might be useful: Pics

To be honest, and I don't know why, but I didn't even think of the brick soaking up the water. Although I do know that the area gets a lot of sun. The planters are quite large but still dry out but that could be the problem. Thanks for the suggestion.

Kathy

You could just drop a plastic planter into you brick ones to help with the water. Lowes $8? I have 4 planters on my porch. only 5" deep x 27" on brackets-and they have 2 spikes and 3 purple wave petunia in each-looks great against my white brick. They each get about 1 1/2 gallons of water, every other day. Can the constant wet soil damage the motar? So lining the planter with plastic is a great idea.