A high tunnel garden is typically a field garden covered by a temporary plastic structure. Essentially it is a greenhouse with a garden inside. The micro-climate created within the structure is ideal for growing plants. Many kit designs are available for purchase with multiple options in dimension, ventilation, and every other aspect you can imagine for a greenhouse. We purchased a 22 x 24 foot gable roof style, 5 mm poly covered kit, with side walls and doors that are able to be raised and lowered. This traps or releases heat, protecting from inclement weather, but still allowing plenty of access within. Some models are able to slide from one section of a field to another on wheels. The high tunnel garden is where I like to grow crops that need a longer time to mature then our climate allows, like tomatoes and peppers. I also get an early start on many vegetables including broccoli and lettuce, and I am able to grow longer into our falls. The first harvests come from crops like kale, spinach, radishes and lettuces, and once those are harvested, they are replaced with warm loving crops like beans and cucumbers. Though these vegetables are very suitable to grow outdoors, I am beginning to harvest spring varieties by the end of May when most of us are just beginning to plant them outdoors. High tunnels are a great way to extend the typical 90 day growing season we are accustomed to. Take note up here, our average last frost date is June 10th, and our average first frost date is September 1st. Because of the high tunnel my growing season lasts typically from March until November. This allows me to grow things like okra, and I can start many vegetables from seed rather than purchasing multiple transplants. The high tunnel also allows me added protection for hardening off those seedlings or transplants we have started indoors. Hardening off is a term we use for acclimating plants to living outside. When you start seedlings in a sunny window or under lights, they need a little time to adjust to the outdoors. The sun’s rays, wind, and weather events can kill a transplant or seedling in hours or days if they haven’t been exposed to those conditions before. Bringing your starters and transplants outside each day, increasing the amount of time they are out over the course of a week or so, can make all the difference in survival of your plants. Try to limit direct sun, heat and wind when you first begin to bring them out. Because I can shelter plants from wind and weather in the high tunnel, it makes an excellent place for acclimating plants that will eventually live permanently in the outside gardens.When you are looking for seeds and transplants it is always a good idea to look for varieties that will reach maturity within that 90 day window, or an indication that the variety is grown specifically for our region. Keep in mind too, that when you purchase transplants, their previous growing conditions will be different from the ones you will plant them in, and acclimating them for a short period of time in their new environment rarely hurts.
Check out these links for more information on high tunnels: