Fall Planting: What to Plant, When to Plant And Why
by Jerry Parsons, Ph.D.,Horticulture Specialist
Why NOW? Common sense tells us that all vegetable crops require a certain growing period before harvest can occur. Experience tells us that certain vegetables require a longer growing period than others to reach maturity.
For instance, vegetables such as beans, cucumbers, okra, tomatoes, pepper, squash, beets, broccoli, cauliflower, Swiss chard, collards, kohlrabi, lettuce, and spinach require at least 2 months of growth before harvest can begin. Crops such as cantaloupe, potatoes, black-eyed peas (Southern peas), corn, eggplant, watermelon, Brussels sprouts, cabbage, carrots, onions, parsley and rutabagas require a growing period of at least 3 months before harvest can occur.
When you realize that the first 6 vegetable crops listed in each of the above categories are warm season vegetables which can be damaged or killed by frost, you quickly understand the urgency of planting certain fall vegetables now. Two months from today is October; 3 months from today is November. Since the San Antonio area's first frost occurs in late November, frost-susceptible crops should be planted or transplanted as soon as possible to insure an adequate harvest period before cold damage occurs.
Planting of the frost-tolerant crops listed can, and should be, delayed until mid-August or September. Why? When soil temperatures are still too hot, the resulting poor seed germination is a real dilemma for fall vegetable producers. Vegetable seeds have optimum soil temperatures at which they will sprout and grow best, and if the soil temperatures exceed the maximum high, they will not sprout at all!
The maximum soil temperature for seeds of cabbage, broccoli, cauliflower, cucumber, corn, okra, cantaloupe, pumpkin, squash, turnip, and watermelon is 105 degrees F. The optimum soil temperature for this group is 90 degrees F.
Vegetable seeds such as snap beans, beets, carrots, chard, eggplant, onion, pepper, radish, and tomato have a maximum soil temperature of 95 degrees F. at which they will germinate; they love 85 degrees F. The cool-soil lovers which will not tolerate soil temperatures above 85 degrees F. but grow like weeds at 75 degrees F. include lima beans, lettuce, parsley, parsnips, peas, and spinach.
What should all of this mean to the fall vegetable gardener? Simple! With air temperature having been over 95 degrees F. for the last several months, soil temperatures will certainly be over 100 degrees F. This means that gardeners will have better success in germinating vegetable seeds in the first category (105 degrees F.). Yet some of the vegetables listed in the second category (maximum temperature of 95 degrees F.) such as eggplant, pepper and tomato must be planted now.
The answer is simple--use transplants of these crops. Healthy transplants of recommended varieties are now available at local nurseries. Crops such as cucumber, okra, cantaloupe, squash, turnips, and watermelon can be planted by seeding directly into the garden area. Wait until later this month or early September to plant seeds of the others.
Soil temperatures can be somewhat modified by adding organic matter which will loosen the soil. Also helpful: mulching and maintaining soil moisture. However, as I indicated last spring, the majority of home gardeners do not own one of the most important growing aids available--a soil thermometer. If you plant seeds in the spring when soil is too cold or in the fall when soil is too hot, the results are the same--disaster! Choose crops carefully for fall planting. Consider the length required to reach maturity, as well as frost tolerance.
Average Dates for First Frosts
To estimate when planting should begin for a particular area, you must know the average first frost date. November 20 is the average first frost date for the area south of a line from Del Rio to Uvalde, San Antonio, Austin and Beaumont. North of this line will experience a first frost date in late October. Gardeners south of a line from Eagle Pass to Pearsall, Pleasanton and Victoria should enjoy frostless days until early December.
Remember these are "average" first frost dates for each region. "Average" means that frost can occur earlier, but, hopefully, it will be much later.
With these frost dates in mind, a gardener can decide which frost-susceptible vegetables to plant, when to plant and whether to use transplants or seeds.
Fall vegetable crops are categorized as long-term and short-term crops. Duration of these crops is dependent upon when the first killing frost occurs and the cold tolerance of the selected vegetables.
Plant long-term, frost-tolerant vegetables together. Frost-tolerant vegetables include beets, broccoli, Brussels sprouts, cabbage, carrots, cauliflower, chard, collards, garlic, kale, lettuce, mustard, onions, parsley, spinach and turnips. Group short-term, frost-susceptible vegetables together so that they can be removed when they die after the first frost. Frost-susceptible vegetables include beans, cantaloupes, corn, cucumbers, eggplants, okra, peas, peppers, Irish potatoes, sweet potatoes, squash, tomatoes and watermelons. (Planting a cereal rye cover crop facilitates frost protection if such a grouping system is used.)
Keep in mind the relative maturity rate, average height and frost sensitivity of various garden vegetables. FS crops (frost-susceptible) will die or be damaged by temperatures below 32 degrees F. FT crops (frost-tolerant) can withstand temperatures below 32 degrees F.
The quick (30-60 days) maturing vegetables are:
Beets (1 ½ feet) FT
Bush beans (1 ½ feet) FS
Leaf lettuce (1 foot) FT
Mustard (1 ½ feet) FT
Radishes (1 ½ feet) FT
Spinach (1 foot) FT
Summer squash (3 feet) FS
Turnips (1 ½ feet) FT
Turnip greens (1 ½ feet) FT
The moderate (60-80 days) maturing vegetables are:
Broccoli (3 feet) FT
Chinese cabbage (1 ½ feet) FT
Carrots (1 foot) FT
Cucumbers (1 foot) FS
Corn (6 feet) FS
Green onions (1 ½ feet) FT
Kohlrabi (1 ½ feet) FT
Lima bush beans (1 ½ feet) FS
Okra (6 feet) FS
Parsley (1 ½) FT
Peppers (3 feet) FS
Cherry tomatoes (4 feet) FS
The slow (80 days or more) maturing vegetables are:
Brussels sprouts (2 feet) FT
Bulb onions (1 ½ feet) FT
Cabbage (1 ½ feet) FT
Cantaloupes (1 foot) FS
Cauliflower (3 feet) FT
Eggplant (3 feet) FS
Garlic (1 foot) FT
Irish potatoes (2 feet) FS
Pumpkins (2 feet) FS
Sweet potatoes (2 feet) FS
Tomatoes (4 feet) FS
Watermelon (1 foot) FS
Winter squash (1 foot) FS
The dates found on the following website are dates during which plants can be grown directly from seeds sown in the garden area. If you decide to plant a certain crop but it is too late to seed directly into the garden soil in your specific region, then you should use transplants. The dates will insure success only if you use the recommended, fast-maturing varieties.