To the Point: Paul Orzolek discusses weather's effect on crops

April 16, 2008

University Park, Pa. -- Farmer's market season is just around the corner. However, those looking forward to buying fresh local vegetables may have to wait just a little bit longer this year.

Micheal Orzolek, professor of vegetable crops and horticulture and director of the Center for Plasticulture, explains how last winter's weather may affect this year's vegetable crops.

(In a related "To the Point" interview here, Paul Knight, Pennsylvania state climatologist and manager of the Penn State Weather Communications Group, compares past winters to the most recent and discusses how this may impact the spring and summer weather.)

How does winter weather impact vegetable crops?

Orzolek: The winter weather helps to recharge irrigation ponds and wells used for irrigation. The cold temperatures also help to kill some insects and weeds. The bad news is that with late spring rains, which we have experienced in Pennsylvania for the last month, fields are saturated. Unless we get warm temperatures (more than 60 degrees F) and some windy days, soils will not dry out very quickly and planting of vegetables may be delayed in 2008. In relation to the entire country, the heavy rains that caused serious flooding in the Midwest will delay planting crops by several weeks.

What does this mean for farmers?

Orzolek: Growers may consider not planting particular crops because of planting delays, or switch to crops that may be more tolerant of wet soils. In any case, I think there will be some spot shortages of vegetables this summer.

When do farmers in warmer climates start to plant vegetables? In some parts of the U.S. is the growing season year-round?

Orzolek: In southern climates such as Florida, Texas, California, Arizona and New Mexico, many crops have already been planted and harvests will begin in early April through late May. Southern Florida can grow almost any crop 12 months of the year.

What about in cooler areas like Pennsylvania -- do farmers here just wait until the ground thaws?

Orzolek: In Pennsylvania, growers start to plant when the chance for the last frost in the spring has passed, based on historical records. For southern Pennsylvania, that last frost date is around May 5. For central Pennsylvania the date is May 20, and for northern Pennsylvania the date is May 31.

In addition to worrying about frost after crops have been planted, growers in the spring also are very concerned about how wet soils are. If soils are tilled too wet in the spring, soil clods develop and the soil will lose some of its tilth (friability). When summer arrives, wet soils that were tilled become very hard and crusted and dramatically affect crop growth and yield.

How important are weather forecasts to farmers?

Orzolek: Wind speed, temperature (both high and low) and rainfall dramatically influence what a grower can do on any given day in the field.

(Media Contacts)

Last Updated March 19, 2009