Alyssum, Ageratum... I use perennial Creeping Jenny as a "ground cover" in some of my patio pots of annuals. It covers the soil nicely, spills over the edges, and looks rather pretty... and it keeps over winter, dormant, when I place the pots in the garage. I clip it back when it gets a little too overgrown.

Once spring arrives, take a trip to your local garden center, and see what low-growing goodies they are offering...

I wanna know why the soil is getting washed out of your pots when it rains? Are your pots overflowing & carrying soil of the pots when water washes over the rim?

Al

I wondered that, too... are the pots, perhaps, positioned under the drip line of your house? A simple rain shouldn't wash away the soil... unless they're right in line with that drip from the porch roof, or splash back from some rainwater source... in which case, the pots need to be moved.

Why not just break up some of those clay pots and use them to block the holes where the soil is running out of? Or just get some old nylons and put your soil in them, then in the pots to grow your plants. I like using Ice plants with geraniums, both flower and compliment each other well.