Whether you sell at a farmers market, roadside stand, or wholesalers, you know how important the first market or delivery day can be. From a financial standpoint, you've been spending money for months on production, and it's high time to start recouping some of those expenses. From a marketing standpoint, your offerings on opening day will set expectations for the season and start to build a customer base.

That's why it's important to have as much produce as possible to sell when your market opens. You need a critical mass of crops ready for harvest; without it, you might decide going to market is not worth the trouble. So if you're going to plant anything to sell early in the season, you might as well plant as much as possible.

Figuring out when to plant so that you have a full table on opening day can be a complicated business. Johnny's has created a Target Harvest Date Calculator that allows you to input the date of your opening day or other big event, then shows you the date to plant various crops. However, this calculator is based on Days to Maturity for each vegetable, and that figure is obtained from the breeders who trial it in the field at a normal planting time. It does not take into account variables such as growing in a hoophouse or Quick Hoops™ tunnel when day length is shorter and temperatures lower than at the normal planting time.

If you use the Target Harvest Date Calculator to configure a production plan for an early market, you will need to make adjustments to the planting dates to reflect conditions at your own farm. How much should you adjust the date? It depends on your specific growing conditions: your latitude, hours of darkness versus hours of daylight, number of sunny days versus those with cloud cover, day-night temperatures, growing methods, and all the other variables, known and unknown.

Eliot Coleman has collected information for his farm in Maine, where he has found that crops grown over the winter can take two, or even three times the published days to maturity (DTM). He addresses this timing aspect of his research in The Winter Harvest Handbook.

Pam Dawling, who writes about vegetable production for Growing for Market, has found at her farm in Virginia that winter sowings are likewise very slow, even in the hoophouse where they have enough warmth. Radishes planted in early September, for example, take 29 days. Those planted in late November take 77 days, and those planted at the end of January take 65 days.

From these examples at two different latitudes, you can see that Days to Maturity is affected by day length as much as by temperature — indeed, light can be the greater delimiting factor with many crops. The best advice we can give is to keep careful records about planting and harvest dates for every crop. Over time, you will have the data to be able to predict how much time to add to the published Days to Maturity for a crop based on your day length and temperature.