by Sally Colby

Zach Lester has an extensive history of growing nearly every kind of vegetable, both outside and indoors. After successfully operating his own Tree and Leaf Farm in Fauquier County, VA, Lester has taken his talent to Potomac Vegetable Farms.

Hui Newcomb and her husband started the 100-acre Potomac Vegetable Farms (PVF) over 50 years ago. Today, Hui and her daughter Hana Newcomb, along with Carrie Nemec, oversee farm operations on acreage in both Purcellville and Vienna, VA.

Lester, who has more than 20 years of experience as a grower, arrived at PVF with extensive knowledge about using high tunnels effectively for growing in all seasons. PVF uses ecoganic practices, which include on-farm composting to build nutrient-dense soil.

“Wherever I land, every ecos is different,” said Lester, adding that PVF is the sixth farm he’s been on. “The soil, weather patterns and dew point are all factors. The first year is a study. Knowledge quantified at one farm might be a different situation at the next.”

For Lester, last year was a time of planning, planting and settling into his role at PVF. He said growing outdoors last winter was difficult, and noted extreme variations over the season, high wind chill and voles as some of the challenges.

Lester said there are positive aspects of growing produce through winter, including leveling the workload throughout the year rather than concentrating the load during the typical six month growing season. Year-round growing helps distribute staff time, energy and labor, but winter challenges led to some changes.

“We decided to downsize our operation,” said Lester. “Our CSA ends in December, and we take January, February and March off.” He said the decision was primarily due to staffing issues and lessons learned last year, including losing about 50 to 60 percent of the harvest.

After seeing the problems caused by both excessive rain and snow melt, Lester is considering measures that will limit snow accumulation and channel water away from the farm’s numerous high tunnels.

“The question is how we’re going to keep excess water from both rain and snow melt away from the tunnels,” said Lester. “It’s nice to be inside the tunnel after a snow. It’s warm in there, and are there are living crops, but we have to get rid of the snow outside the tunnel because it’s going to cause flooding.” He said a snow blower helps eliminate some of the snow, but he is working toward dedicated drainage to move water away from between the tunnels.

“The rest of PVF is large fields with big rotations,” said Lester. “We can drive all over the place, but by winter, we don’t want to do that. We just want to go into the tunnel or to the row cover, then walk to the shed without having to drive through a muddy field. We need drain tile and an apron so water coming from above can continue to flow downward.”

Lester said ventilation is critical for high tunnel crops no matter what time of year they’re used. “Roll-up sides are easier to ventilate, but they’re really costly,” he said. “With roll-up sides, I could open the north side just a little and open the south side much higher for ventilation.”

Rather than spending money on roll-up sides, Lester concentrated on end-wall ventilation. This includes folding doors designed to open completely, providing good air flow any time of year. When temperatures are in the 40s, Lester opens the tunnel end doors and closes them by early afternoon. On cloudy, rainy days, he still opens the doors for air circulation, and on windy days, just one door is open.

“If it isn’t too windy but it’s cold outside, I’ll open up because crops are covered with a cloche,” said Lester. “We want the air in there. Open end-walls require sturdy construction with solid sill boards and frames that keep the entire structure stable.”

Several caterpillar tunnels on the farm are used for winter growing. “I had some smaller, shorter ones,” said Lester. “Some are too tall, and if there’s a lot of snow, even with a center truss, snow gathers on them and makes the tunnel more vulnerable to wind. I have to work really hard to keep the snow off to keep the tunnel up.” Although he uses some caterpillar tunnels, his experience with growing in several locations confirms his belief that winter growing is more successful in high tunnels.

Lester did some shallow tillage in tunnels last year, and will probably continue the practice. “I was going to be asking more from the soil in the tunnels than from a field,” he said. “We ripped the soil to about 18 inches before the tunnels were put up here, and I used a rotary spader that goes down to 12 inches.” Ongoing tillage will be closer to four inches as Lester concentrates on improving soil tilth.

After experimenting with various mulches and landscape fabric, Lester has seen benefits and disadvantages. “I’m trying to keep any kind of cover off as long as possible because of the vole population,” he said. “We’ve used vole traps, which aren’t very effective and smell really bad. We’re experimenting with buckets of water … but we’ve had so much water that the buckets pop out of the ground.” Lester plans to discontinue growing root crops in tunnels over winter because losses to voles are too high.

Weed management is an ongoing issue, and Lester said flame weeding is a good option. “We wet all the beds and create a lot of steam,” he said. “That seems to help, but there’s still work to be done.” Lester allows weeds in the tunnels get a little bigger so he can weed by hand and remove them. However, sometimes embedded root masses result in weeds returning.

Drip irrigation helps seedlings get a good start in tunnels. “I’m doing a lot of succession plantings,” said Lester. “When everything is set, I use some overhead irrigation. The head line outside might be frozen, but I can set up a center row of wobblers.”

After seeing extensive hail damage to the high tunnel covers last season, Lester is considering an additional layer of plastic on the tops of high tunnels to provide another layer of insulation. In addition to managing water runoff, Lester’s long term plans for PVF include electricity for the propagation house, which would also provide electricity to run fans in the high tunnels.

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