The Land: Fighting the freeze.

April 20, 2021

The Land: Fighting the freeze.

The Land is series telling the stories about local agriculture. It is a presentation of Peterson Farms, Inc., www.petersonfarmsinc.com.

By Allison Scarbrough, Editor.

HART — Dave Rennhack has been a farmer for decades and has dealt with many spring frosts over the years that have damaged fruit in his orchards.

Warm and sunny weather two weeks ago gave rise to budding orchards, only to be followed by cold conditions now with freezing nighttime temperatures.

But Rennhack is prepared for the frost fight. He invested in 12 propane-powered frost fans that help protect his precious trees from Mother Nature’s fickle ways.

“We are mainly apples, but we do sweet and tart cherries, peaches, plumbs, nectarines, apricots, sweet corn, tomatoes, peppers, melons and pumpkins.” Much of his bounty is sold at Rennhack Orchards Market on Polk Road, which he and his wife Joann own. Their 120-acre farm is situated on 72nd Avenue just down the road from the market.

“This is a farm my wife’s family (Piegols) has had for three or four generations. My son-in-law (Jeremiah Palmer) is in the operation now with plans to take it over as I fade away.”

Rennhack installed the first wind machine in 2008 for frost protection. “After the bad freezes of 2012, we had three in. After 2012, we put another nine up.

“If you live in Michigan, you have frost. You might not have it every year, but in a five-year period, you have it a few times. Once every 10 years, you have it severe. So, we figured we’re in the business long-term. Economically it’s not good to not have a crop and psychologically it’s not good to not have a crop. This way, we at least feel we’re doing what we can.”

The machines work best on a night when you have an “inversion.” What’s an inversion? “There is a layer in the atmosphere about 80 or 100 feet up off the ground that traps the cold air above it. As the warm air from the ground radiates out at night, it kind of traps it at that level.

“It’s like in the winter time when people are burning their wood furnaces, you see the smoke go up on a clear day and then it kind of levels out. That’s the inversion layer it’s going up to, and it won’t go up through that.

“We had some good inversions last Friday and Saturday nights, and we ran the machines about four or five hours those two nights, and we could raise the temperature about two or three degrees pretty quickly in the orchards. 

“Tonight, I don’t think we’re going to have an inversion or a very weak one,” Rennhack said Tuesday, April 20. “Because you need fairly calm conditions to have an inversion, and we’re only supposed to get down to 4 or 5 mile per hour winds.” Cloud cover is also another inversion preventer, he said. “Tonight I don’t think our wind machines are going to be as impactful.” The previous night, Monday April 19, was also too breezy. 

Unfortunately, Tuesday’s forecast is calling for “critical temperatures. They’re talking 24 or 25 (degrees). If it gets down below 25, cherries are going to get hit pretty hard. Apples will start getting damage at about 27. They will get severe damage if it gets down to 21 or 22.”

There are two main concerns: losing the fruit itself and getting frost scars on the fruit. The apples could survive, but they may have a blemish on it, he said. “Primarily our markets are all fresh.” If the fruit has marks on it, it will go to the processing market.

“We run the machines not only to save fruit but to save fruit finish.

“If you’re in it as many years as I have been, you don’t like years like this but they’re not abnormal.”

The fans are about 30 feet off the ground with a 19-foot diameter. “They claim that you can protect about 10 acres with one machine. We see very effective protection at about 6 acres to 8 acres.” Each fan is an investment of approximately $35,000. Each fan has its own thermometer with an autostart feature. Eventually, there will be a smart phone app to monitor the system. 

Since the devastating impacts of 2012, more local farmers began using the fan system, he said. 

Rennhack does not let the cold weather threat deter him. “If this is the worst thing that happens in 2021, we can live with it.”

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