Clay pots need to be cleaned.

Clay pots need to be cleaned before spring planting. Clay pots need to be washed and scrubbed with bleach and rinsed in water before replanting flowers. Let them dry in the sun.
The discarded old soil from the pots can be recycled and thrown into a compost pile or used in your flower beds.
During the winter months store the clay pots in a dry area like the garage so they won't crack during the first frost.
If the clay pots get cracked brake them up and use them to provide drainage for your plants. Put the pieces at the bottom of the pot and cover with soil.
You should have healthy flowers spouting up out of your clay pots.