Ask Mr. Smarty Plants

In "Just for Texans" in the Collections Section, there is a list of the plants that have seeds in the Lady Bird Legacy Mix. You can go to that list and follow each link to the page on that wildflower to learn when it blooms, and what it needs to prosper. Of these, 8, including Lupinus texensis (Texas bluebonnet) and Castilleja indivisa (entireleaf Indian paintbrush), are annuals and 4, including Oenothera speciosa (pinkladies) and Callirhoe involucrata (purple poppymallow) are perennials. For all of them, the predominant blooming season is March to May, but the evening primrose blooms from February to July and is semi-evergreen, making it something to look at in the wildflower garden when other plants are fading. 

All of this is to say that, in Nature, this sort of problem kind of takes care of itself. The wildflower mix you are referring to was very carefully chosen, we're sure, to emulate the wildflower meadows Central Texas is famous for. However, evening primroses can be sneakily invasive; when they are dormant in the winter or during a hot, dry summer, the roots will still be spreading and new plants can pop up where you didn't expect them. About the best advice we can give you is to allow plants to bloom and then pull them out before they go to seed. Individual flowers only last one day, but you can keep an eye on them and when seed pods begin to appear, out they come. Since it is a good, long-blooming groundcover plant, we would certainly recommend that you leave some, and not try to exterminate them. Then, after noting what plants from the Mix are or are not coming up, you might choose to reseed only with the individual seeds of the particular plants you are missing. You didn't say how long you have had your wildflower garden, but we're sure you know that new seeds should be planted in the Fall. With any seed mix, you take your chances on what will do well in the space and what will not. Even the annuals in the mix will self-seed and return without further seeding, so additional over-seeding is best used to add diversity. If some species do not do well, or even come up, two years in a row, you might consider the soil and growing conditions each prefers. 

Species in the Lady Bird Legacy Wildflower Mix from our Native Plant Image Gallery:

Castilleja indivisa

Callirhoe involucrata

Coreopsis tinctoria

Echinacea purpurea

Eustoma exaltatum ssp. russellianum

Gaillardia pulchella

Glandularia bipinnatifida

Lupinus texensis

Monarda citriodora

Oenothera speciosa

Phlox drummondii

Rudbeckia hirta