Ask Mr. Smarty Plants

You probably would be interested in something that is evergreen or semi-evergreen that will keep your window boxes looking nice even in winter. Gray Sagewort or Prairie Sage (Artemisia ludoviciana) is a perennial evergreen with silver green foliage. Its flowers are rather inconspicuous but it could be combined with other plants with showier flowers. Two plants with yellow flowers that bloom spring through fall and remain evergreen in mild winters are Zexmenia or Texas Creeping-oxeye (Wedelia texana) and Damianita (Chrysactinia mexicana). All three of the above plants can grow reasonably tall (1-3 feet) but can be controlled by trimming. A shorter white flower that is semi-evergreen is the Blackfoot Daisy (Melampodium leucanthum)

If you are looking for something to produce showy flowers for the spring and summer, there are several annuals that would do nicely. All of the following have long bloom periods, from early spring till first frost.
1. Lazy daisy (Aphanostephus skirrhobasis)
2. Indian Blanket (Gaillardia pulchella)
3. Greenthread (Thelesperma filifolium)
4. Prairie Verbena (Glandularia bipinnatifida)

Some perennials with long bloom periods are:
1. Western Primrose (Calylophus hartwegii) or Square-bud Primrose (Calylophus berlandieri)
2. Violet Wild Petunia (Ruellia nudiflora)
3. Pink Evening Primrose (Oenothera speciosa)

You should realize that all the native plants named above will also grow in the ground in your area of Texas.

You can visit the National Suppliers Directory in the Native Plant Information Network to search for nurseries or seed companies that specialize in native plants in your area.