Minutes August 15 — Growing Vegetables Under Cover

Gardeners Exchange Group Meeting 15 August 2015
Location: Walnut Hill, Home of David and Missy Hill
Topic: Growing Vegetables Under Cover, by David Hill
Submitted by Julie Neely, GEG Secretary

David Hill owns and operates Hill’s Farm Fresh Produce LLC. You may purchase his produce at the Fresh Fruit and Veggie Wagon located at the corner of Old Country Club Road and Highway 340. The tour focused on the use of the greenhouse, high tunnels, and techniques designed to minimize disease and enhance overall production and quality.

Dave grows and sells cucumbers, tomatoes, peppers, Kale, broccoli, and lettuce on the farm, but the tomatoes are grown exclusively in the high tunnels. Over 5 tons of tomatoes were produced this year, and owing to his techniques he experience less than 5% fruit loss. You really can’t argue with that kind of success. Dave commented that the time to successfully produce and sell farm produce has arrived. He only wishes he had planned and started more veggies to sell and next year he will be ready!

The Green House

David’s veggies start life in the climate-controlled greenhouse as seeds planted into sterile potting medium. They germinate under cover at 78 degrees in 10-14 days and are then transferred to the 75-degree light chamber until they grow their second set of leaves (true leaves not the cotyledons). At this point they are transplanted from the starter plastic trays into 2-inch pots, and after 5-6 weeks they go from the green house into the high tunnels to harden off for a couple of days before being taken out of their pots and “planted.”

The High Tunnels

Dave’s high tunnels are 14 feet tall, 25 feet wide and 75 feet long, and they are fully screened — no bugs get in or out. They are loaded with healthy, productive vegetable plants. The tomatoes are grown in 5-gallon plastic grow bags full of compost with drainage holes in the bottom. (Compost is purchased from Lyle Tabb and does contain some weeds which are pulled routinely). Dave explained that, “all soil east of the Mississippi is contaminated with early and late tomato blight.”

Blight is a fungal disease spread by wind-borne spores which germinate on wet leaves, especially tomato, pepper and egg plant. Anything that prevents the leaves from being wet will help prevent blight because once infected the plants will eventually die. So watering early in the day, planting in full sun (at least 14 hours a day), keeping plants pruned and thinned to allow good air circulation, rotating crops, keeping plants off the ground to avoid soil splash up, and a good winter clean-up of dead leaves and plants all help reduce blight — or you can use fungicide. But the best way to avoid blight is the use of a green house or high tunnel and soil-free bags of compost.

The high tunnel prevents the leaves from getting wet. Dave’s irrigation system waters only the bag of compost containing the roots (not the leaves). He trains the vines using plastic clips to grow up cords hung from the ceiling of the high tunnel which prevents the plants from ever touching contaminated soil. Two tomato plants are grown in each 5-gallon bag and these are pruned to 4 runners; this limits overall yield but allows ventilation between plants and combined with pinching off over-abundant blooms, produces large, uniformly perfect fruit ready for the farm market. The tomatoes in the high tunnels demand 4-6 hours per day of labor to keep them fertilized, weeded, pruned, and clipped to the cords on which they grow and of course are harvested. High tunnels combined with row covers in the winter extend the growing season dramatically; Dave grows vegetables inside his passive solar high tunnels even when the outside temperature is 25 degrees.

So what are the disadvantages to using high tunnels? They cost money; prices vary but Dave’s basic model cost $7,500. They get very hot in the summer; shade cloth over the exterior helps. They need an irrigation system or you will spend all your time hand-watering. They benefit from a heating system, depending on what you are trying to grow in the winter. It helps to have pollinators introduced into them because they are totally enclosed — no bugs get in or out. Dave uses leaf cutter and mason bees. These non-honey producing/non-colony forming bees are easy to propagate in little paper/cardboard tubes which they will fill with eggs the first year. You just harvest the tubes and replace them into your high tunnel in the next growing season. The bees are happy to pollinate your plants, which saves you from having to spread pollen yourself by shaking plants and cords, a very messy and sneezy task.

Some vegetable varieties that Dave grows and likes are the Salanova lettuce varieties, which grows beautifully in the shaded tunnels even in mid-August (available from Johnny’s Select Seeds), and determinant tomato varieties such as Mountain Fresh, Primo Red, Scarlet Red, and Red Challenger, which have blight resistance. Next year he plans to grow grafted heirloom tomato varieties such as Black Krim, Royal Hillbilly, and Pink Ponderosa — grafting the non-blight-resistant heirloom onto resistant rootstock helps fight the early blight to which heirlooms are susceptible.