Record-breaking cold temperatures rolled in, and a freeze warning was issued for several nights in a row this week. The farmers in Redland scrambled to protect their crops from the freezing cold, but generally fared well. CSA growers located further north — Worden Farms in Punta Gorda, and C&B Farms in Clewiston — got frost damage on Tuesday night. They’re still evaluating how much damage they got, and if any crops were lost.
As a result, there may be less in the share box this Saturday and maybe for the next week or so. Freeze damage is one reason, and less veggies growing is another. “Plants don’t like to grow when it’s cold. They like to go dormant,” grower Dan Howard explained to me. If there’s a killer frost and lettuce (for example) is burned by cold, that’s it, there’s no more local lettuce to eat until it’s replanted and harvested again. Remember, as CSA members, you agreed to share the same risks as the growers! No faking it with lettuce from Belize or somewhere… not in this CSA! (Also, because vegetables were damaged by the cold, or were not ready to pick, there will be less in the stores and the prices will go up.)
Reemay, or floating row cover, protects delicate greens and pole beans against freeze damage.
Margie Pikarsky at Bee Heaven Farm protected delicate basil, heirloom tomatoes, and pole beans with large sheets of Reemay, or floating row cover. It’s a spun polyester fabric that is used to cover plants, much like a blanket. The row cover acts like a blanket to hold in the heat and keep plants warm. Margie added she’s not watering as much, because that runs the risk of plants mildewing, or hot condensation cooking entire plants. Her crops have been covered since the first freeze warnings on Saturday, and the Reemay will stay up until the cold blast forecast for this coming weekend.
On Wednesday afternoon, Dan Howard of Homestead Organics, was cautiously optimistic. “Tuesday night it went down to 33, 34 degrees, but not a killer freeze,” he told me. He had prepared his bean fields by watering them quite extensively during the day on Tuesday. (It’s just too much acreage to use row cover.) Dan explained that his crews “soaked the ground down real good. Water insulates the ground to keep it from getting colder. Well water is 75 degrees, the same temperature year round. Dry ground gets colder than wet ground.” He explained that ground temperature is the most important for the plants, keeps the roots from freezing.
If the temperature gets below 32 for any length of time, plants will become permanently damaged from the cold. “Anything below 32 is bad, and at temps of 28, 29 degrees, it’s a total loss,” Dan explained. Monday night wasn’t that severe because there was a blanket of cloud cover, which acted as insulation and kept the temperatures from dropping too low. Tuesday night the sky was clear and temperatures dropped — but it was windy, and that made a difference. The moving air keeps ice from forming on the leaves. “If there’s no wind and clear sky, you get frost,” Dan said. And frost is what kills plants. It coats the leaves and burns them much like frostbite. Leaves turn black and wilted from the damage and the plant will die. Farmers can knock ice off the plants by spraying fields with water in the middle of the night, Dan explained. That’s why they’re up all night, watching the temps, checking the plants watering in the fields and groves.
In a similar vein, Robert Barnum of Possum Trot Nursery watered his tropical fruit grove on Tuesday night. He has giant pumps to draw well water, and tree-high sprinklers dotted through his grove. Tuesday night temps dropped to 36, and Robert was up at midnight and again at 3 am watering and checking on his trees. He explained that water gives off heat as it freezes, 353 kilocalories per gram of water to be exact, and that bit of heating warms the plants. Once the water on the plant freezes, it keeps the temperature constant at 32 degrees even if air temperatures drop below that, because a heavy coat of ice acts as insulation. But you have to keep watering, he insisted, to keep that small but important heating process going.
By Wednesday night Robert was less optimistic than Dan, and said the thermometer already read 39 degrees at 9 pm. The sky was clear and the winds were dying down. It looked like there would be a killer frost that night. Margie said the temperature dropped hard and fast — and then something unexpected happened. Some light cloud cover rolled in, and those clouds were enough to act like a blanket keeping heat from radiating away from the ground at night. Temps hovered around freezing, then came back up a bit. “I never saw anything like that,” Margie told me. But the main reason why the anticipated killer frost didn’t happen, according to Jonathan Crane at TREC: when the temperature fell to 35 it also reached the dew point. When the temperature meets the dew point, heat is released and the temperature rises, and that is what happened on Wednesday night. (There might have also been a bit of ground fog.) End result, no freeze, and crops were spared — this time. A more severe blast of cold air is forecast for the weekend, and growers (especially to the north of us) are bracing themselves.
To learn more about how frost forms and dew point, take a look at this web page.
Redland Rambles 