HOME & AG: Planters can dodge late freezes

Apr. 21—As Cleveland County has hit the last average frost date, which was April 15, a local educator wants to talk about the birds and the freeze.

"That's just an average. Cleveland County has freezes as late as May 3," said Courtney DeKalb-Myers, horticulture educator at Cleveland County Oklahoma State University Extension,

DeKalb-Myers said gardeners still need to be on their guard, as Norman has experienced freezes as late as May 3 in 2013.

"Late freezes can be hard on our plants. Late freezes can also be hard on gardeners who've already started planting," she said. "If you fall into that category, you're not alone. It's easy to get bitten by spring fever when we're having sunny days in the 70s."

Connor Bruce, meteorologist for the National Weather Center, said the Oklahoma panhandle is expected to reach a low of 33 degrees Saturday, which means there is a possibility it could freeze.

Bruce said in Norman, locals will not experience freezing temperatures this week, but it is possible in the next month, as the meteorology center is anticipating lows in the 30s.

"In general, the latest freeze has been occurring in early to mid April or in late March, which is typical," he said. "There are larger scale features to consider like El Niño and La Niña that can influence weather patterns over the last 10 years."

This year's last freeze took place on March 19, and in 2021, the last freeze took place April 21, according to a report prepared for The Transcript by The National Weather Center.

DeKalb-Myers said late freezes can hurt crops because many growers don't anticipate them. Because of warm temperatures, shoots and leaves have shot out, giving subfreezing temperatures a greater opportunity to cause damage.

"Cold damage results from water freezing within the plant cells. Ice crystals are formed and can puncture the cell wall," she said. "Salts and sugars within the plant cell lower the freezing point, so air temperature must be 29 F or lower for this to occur.

"The piercing of plant cells creates a water-soaked appearance on the damaged leaves. Freeze damage can also appear as brown leaves or edges, wilting, tip dieback, and plant collapse."

DeKalb-Myers said cool season vegetables, like broccoli, kale, carrots, or spinach, can survive temperatures as low as 26 degrees, and cool season annuals, like pansies, are similar.

"New growth on trees and shrubs can be susceptible to freezing temperatures, but it's common for them to drop the damaged growth and emerge with new leaves a few weeks later," she said.

To combat cold temperatures, the educator recommends conditioning plants. For plants in greenhouses or indoors, she recommends moving them outside so they have an opportunity to "toughen up" before a possible freeze.

"To harden plants, place them outside while they are still in the container on warm days," she said. "This exposes the young plant to the elements, allowing it to toughen up."

To save plants from freezing temperatures, it is also important for growers to be aware of the temperature. On days where temperatures may drop, DeKalb-Myers recommends covering them with a plastic covering to create a mini greenhouse effect to lock in heat.

"Frost cloth can be purchased, but it's also possible to get creative," she said. "Two-liter bottles, milk jugs, and plastic totes are highly effective, but make sure the plants are not touching the plastic. Old sheets and hay can also be used."

She also recommends watering plants, especially before potential freezes because drought-stressed plants are more susceptible to cold damage.

"Additionally, moist soil will retain a warmer temperature longer," she said.

Brian King covers education and politics for The Transcript. Reach him at bking@normantranscript.com.