A Master Gardener will know the ideal dates to plant and harvest each crop, but a Casual Tiller like myself requires a simpler scheme, so I go with holidays. Tomatoes and hot peppers go in after Valentine's Day; broccoli comes out on St. Pat's.
Parsley and cilantro get planted after Labor Day, and just about every other cold weather crop gets seeded or transplanted on Columbus Day or after Halloween. An exception is the radish, which has varieties that can be planted after any fall holiday, Christmas or Hanukkah, and will grow in Houston.
To cultivate them, it's best to start with very rich soil, because radishes grow fast, and they'll mature in a month, before the chance to fertilize them. Since radishes grow so fast, the seeds can be sowed every week, from Labor Day through New Year's Day, for a steady crop. Just make sure to plant the seeds shallow, in full sun, and thin the sprouts to give each plant one or two inches of space.
Some Wild Selections The reliable variety for Gulf Coast Texas is Champion. For fun, I chose the Sparkler variety, which is half white and half crimson. Believe it or not, there's a variety called the French Breakfast, should you prefer eating radishes in the morning instead of a donut.
If you begin around Labor Day, or wait until Martin Luther King Day, you can plant daikons, the Asian white radishes that are also grown commercially in the Houston area. For an unusual treat, these times are also ideal for planting the Munich Bier Radish, a large variety which is sliced thin, salted, and sometimes buttered to cut the pungency, and enjoyed with a dark German beer. Probst!