I lived in Houston for 30 years and you and I are still in the same zone...
1. All kinds of zinnias...best ones are in seed catalogs...like Park Seeds, (look in Garden Watchdog for good seed companies)(it is not too late to throw seeds(Benary's Giants are good ones)
2. Indian Summer is the best rudbeckia for cutting
3. (plant snapdragon plants in November ...Liberty is the best cultivar for Houston...and then you have blooms through April
4. Larkspur is another you can throw out seeds in November and cut in April
5. Cosmos (both tall and bipinatus are great cutting flowers for summer)(grow great when hand thrown seeds)
6. Try to find some of the new kinds of Celosia...not the old ones for summer (like Bombay series)
7. All kinds of coneflowers (echinacea) purple, pink and white...yellow,etc.
8.Gomphrena or Globe Amaranth
9. Shasta Daisy 'Crazy Daisy' is a good cutting one
10. Marigold,,,there are some good tall ones that will take Houston's heat
11. Nicotiana sylvestris (this is the really tall white flowering tobacco)
12. Get some perennials going in the fall for you to cut in the spring...Foxglove 'Foxy', Siberian Iris,
good luck...have to watch Spurs play!!