How can I plant in my cement BIRDBATH?

https://empressofdirt.net/birdbath-planters/

https://www.pinterest.com/explore/bird-bath-planter/

https://homeguides.sfgate.com/plants-birdbath-55998.html

What you plant will depend on the "Zone" you are in. Also, usually bird baths are rather shallow so you'll need to consider types of plants with shallow roots. Perhaps some kind of miniature pine trees/bushes would work well.

Pansies! They only take the depth of the birdbath in potting soil. And they last until they get frozen out. Most evergreen plants need a lot more soil, but Boston Ivy should spread in the birdbath. And consider spray painting the cement base. Even if it peels in a couple of years, that will add to the charm. Best wishes, again, Gle. You will have a lovely yard. ☺️

Try some of these.

http://www.costafarms.com/get-growing/slideshow/12-annual-flowers-that-can-take-the-cold

They don't mention ornamental cabbage. I have seen that stuff in the snow and still colorful.

PS I live in central Virginia Richmond/Henrico, & Chesterfield.

When you raise a plant off of the ground there is little protection from the cold for the roots and they are more likely to freeze and the plant die. Why not try a low bucket with something like pine branches and berry sprigs that will last all winter in the cold. You can add water and it will freeze making it hard for the winter winds to knock over.