There’s always more to learn

Growing greens year-round at Twin Springs Fruit Farm in Ortanna, PA, started accidentally.

“This house was built to grow ‘Tulameen’ raspberries starting in February,” said Tom Childs, greenhouse manager since 2000. “They came in dormant in pots. But 1999 was a drought year, and the only growth that came out was green right out of the pots. In February, the fruiting canes were dead so we yanked them all out. I knew arugula was sold at markets, so we grew some arugula, and that’s what we’ve grown in this house since.”

Twin Springs has four gutter-connect production houses and a transplant house, along with a greenhouse where greens are grown year-round for a total of 32,000 square feet of growing space.

There have been numerous changes since Childs began managing the farm, including converting the benches in the greens house.

“We were growing on the ground on four-foot-wide beds with plastic liners,” said Childs, explaining the change made seven years ago. “Now we have rolling benches. Everything is up off the ground, which is what the food safety people prefer. The crew likes it much better, and everything about it is faster. It turned out to be a big improvement.”

Greens are grown in a compost- based, soilless blend, which works well but requires maintenance. Childs said if the medium becomes too dry, it doesn’t re-wet easily, so it can be difcult to keep beds balanced. However, compost is high in potassium and has a higher water-holding capacity without being saturated.

Childs said the medium has a fairly high pH – 7.5 at the highest. “We were probably adding more [compost] than we needed,” he said. “The beds are about five inches deep and we were adding about an inch at replanting.”

Because each bed has a high plant count and greens are grown year-round, maintaining a balanced growing medium is critical. When Childs first started at Twin Springs, he was treating the greens like all the other greenhouse crops. The result was salt accumulation and fertilizer imbalance. Plants germinated and started to grow, then fell over. Today, monthly soil tests for each of the 10 beds helps prevent nutrient imbalances.

“We grow tomatoes, cucumbers, peppers and lettuce [in greenhouses], so buying a lot of different premixes doesn’t make sense,” said Childs. “We purchase base components by the skid and blend it ourselves. All the fertilizer mixes are different and are applied according to crop needs. In the last few months, we’ve had the highest production ever.”

Preparing the beds for planting involves several pieces of equipment made on the farm. One useful tool is a hand-held tiller with rototiller blades from a chainsaw mounted on three-quarter-inch allthread, operated with a half-inch variable speed right angle drill. Two experienced workers can go end-to end in a few minutes, then the bed is edged and smoothed.

“The entire growing cycle is about 80 days from seed until removing the crop and starting over,” said Childs. “When we’re about to tear out a row, we do a kill spray with AzaGuard™. It smothers and has a pyrethrin.”

Drip irrigation keeps tender plants growing well. Childs uses six-inch emitters with a 0.5 gallon/hour flow rate. Because one side of this house has more sun exposure, certain areas dry more quickly, so the crew keeps an eye on soil and plant conditions.

During peak growing conditions, the time from seed to rst cut for arugula is 24 days. “We cut every nine or 10 days after that,” said Childs. “The beds are ve feet by 84 feet, so we’re growing greens on a little over 400 square feet. On the rst cut, we typically get 400 threequarter-pound bags. The rst cut is always the best, then it drops off. We usually get six cuts, and by then it’s time to re-do the beds. If we get four to six cuts we’re happy.”

By the sixth cut, they might be down to 175 bags. In ideal conditions, the greenhouse yields about 1,300 to 1,400 to bags of spring mix and arugula weekly.

Twin Springs experiences many of the same insect problems as other growers. All greenhouses are screened, which doesn’t eliminate aphids, but it helps a lot. Thrips can be a problem, but the diamondback moth (DBM) is the most challenging.

Childs referred to DBM as the poster child for resistance but has had success with SPEAR LEP with Leprotec. “One is a peptide that makes the Bt work better,” he said. “We’ve also had some success with using the upper rate for XenTari, another Bt. We also use Azera, an organic growth regulator for soft-bodied insects, which has a pyrethrin and azadirachtin. When we plant, we put on Admire (imidacloprid) and that’s the only time it’s used. That gives us two weeks’ protection from aphids from the start.”

Twin Springs is present at 21 markets in the D.C. area during the primary growing season, and 10 markets in winter. The drop in production during winter coincides with fewer markets. Storage crops, fresh lettuce from the hydroponic bay and year-round cucumbers round out market selections.

“By the middle of February, light improves significantly,” said Childs. “Light meters measure the light intensity of the LEDs. We set the lights to turn on and off through the day at an intensity threshold. In winter, the lights are on all day, even in full sun.”

One ongoing problem has been high greenhouse temperatures in summer. Childs said excess heat occurs during a fairly short period of about eight weeks starting in early July, and severely affects production.

“It can be up to 100º during the day, which induces the arugula to bolt,” he said. “As an experiment, we’re going to put on about 80% shade in attempt to cut heat, but that will cut too much sunlight so we’ll run the lights.”

In mid-June, Childs will put the regular shade that’s always used. When temperatures rise, an additional 50% reflective cover will be added to reflect infrared rays. Childs expects the cover will help control summer heat. This move will cut light to the point it’ll be too dark to grow, with the house darker than it is in winter. Lights that wouldn’t normally be needed will be on to provide adequate light. This plan will also allow more work time and better working conditions.

Through the years, Childs has tried numerous techniques, many of which he came up with himself. Each idea has been tested and fine-tuned before being adopted or rejected.

“After a 25-year evolution of the system,” said Childs, “I think we might have it right.”

by Sally Colby