A question I'm often asked by market gardeners is, "Is there a tool or guide I can use to schedule plantings to ensure a continuous harvest? I need to have a consistent supply of product to keep my customers satisfied." My usual response is yes and no. Yes, there are tools available to assist growers in developing their own planting schedule, and no, there is no such thing as a "one size fits all" planting schedule.
When developing a planting schedule, keep in mind there is no schedule that can guarantee a continuous harvest. Assuming your crops survive multiple assaults from freezing temperatures, flooding rain, hail, wind and pest organisms, there will always be annual variance in soil temperature and moisture content, air temperature and sunlight availability. These factors not only influence initial harvest date, but the harvest frequency and yield distribution for any crop harvested multiple times from a single planting. Variable weather is the primary reason why it is impossible to develop a planting schedule for continuous harvest of field-grown vegetables that guarantees consistent results from year to year.
The easiest and most direct planting approach is to copy the schedule of a successful grower in your vicinity. Keep in mind you will need to use the same varieties and same production techniques. Of course, this assumes your neighbor is willing to share this information with you.
Most growers incorporate the use of varieties having different maturity dates and successive plantings of a single variety when developing a planting schedule for continuous harvest. These two techniques are often combined.
Novice growers or growers who don't keep production records often resort to a "shotgun" approach when scheduling successive plantings, hoping that if they stagger enough plantings, sufficient overlap will occur to ensure a continuous harvest.
A more accurate and less costly method of scheduling for continuous harvest incorporates the use of yield distribution profiles. With most vegetable crops that are harvested multiple times from a single planting, yield increases over time until a peak is reached, after which it decreases gradually. If your goal is to achieve a continuous, consistent harvest, schedule plantings so that the initial harvest of the most recent planting coincides with the peak harvest of the planting before it. In theory, the increasing yield of the later planting compensates for the decreasing yield of the earlier planting. The use of yield distribution profiles to schedule planting dates is not an exact science due to an ever changing growing environment, but it sure beats the shotgun approach.
Jim Motes, Ph.D., former state vegetable crop specialist with the Oklahoma State University Cooperative Extension Service, developed a planting and harvesting schedule for Oklahoma that lists yield distribution profiles for a wide range of fruit and vegetable crops. I use Dr. Motes' publication regularly when developing planting schedules for continuous harvest. It doesn't take the place of good production records, but I've found it to be the next best thing. To obtain a copy of Dr. Motes' planting and harvesting schedule, contact the Ag Helpline at 580-224-6500.