Efficient Layout, Bed Preparation and Crop Selection for High Tunnels
Adding a high tunnel or greenhouse to your commercial farm or home garden is a considerable investment and in order to quickly maximize your return, the growing space should be efficiently managed both in terms of high tunnel bed layout, bed preparation techniques, and crop selection. The total growing area square footage of a high tunnel is the measurement of the width multiplied by its length and most often, at least 30% of that will be allocated to paths or walkways, so it is especially important to create an efficient bed layout to maximize the use of the interior growing space. Over the years, I have visited many farms and witnessed various high tunnel layout designs but the most efficient layout follows a standard 30-inch wide bed with 12-inch wide pathways. Imagine you have a 20-foot by 50-foot high tunnel, which equals a maximum of 1000 square feet of interior growing space. For instance, if this high tunnel is laid out longitudinally using 30-inch wide beds with 12-inch paths in between and we leave 2 feet on either end as an entrance walkway area, this configuration leaves us 6 beds at 46 feet long for a total of 690 square feet of actual growing space. With only 690 square feet of actual growing space, it is critically important to select appropriate crops to take advantage of the specific growing season including the season extension benefits of a protected growing space as well as the increased vertical growing space of the high tunnel. Below are some simple steps for bed layout and bed preparation as well as some tips for selecting crops to maximize production.
Simple Steps for High Tunnel Bed Layout:
1. Collect all necessary tools and supplies for bed layout including a roll of 800’ Mason String on reel, wooden stakes, hammers, two 50-foot tape measures, shovels, and bed preparation rakes (which can be sourced from Johnny’s Selected Seeds)
2. After initial rototilling of soil, extend one 50-foot tape measure along the width of the high tunnel, and then extend the other along the opposite width of the tunnel.
3. Beginning at one end of the tape measure, hammer wooden stakes into the soil at consecutive intervals of 30-inch wide beds, followed by 12-inch wide paths (or your chosen measurements).
4. Follow the same steps for the tape measure at the opposite end of the tunnel.
5. Attach the mason string to a stake marking the path on the far right or left side of the tunnel and extend the string to the opposite stake at the other end of the tunnel, securely wrap the string around this stake, then around the adjacent path stake, finally bring the string back to the front of the tunnel effectively marking the pathway.
6. Keeping the string elevated above the soil surface, continue unspooling the string in this fashion to mark the next bed, and then the next path, and so forth until all of the beds and paths have been marked with the string.
7. Next, take a shovel and begin shoveling the top 2-inches of soil from the path and place on top of the adjacent beds as you make your way down each pathway. Continue until all pathways are clearly defined as ‘sunken paths.’ Remove the string by rolling up the reel.
Simple Steps for Bed Preparation Prior to Direct Seeding or Transplanting:
1. Collect all necessary tools and supplies for bed preparation including Bed Preparation Rake; Tilther with a battery powered drill; or a 3-Tooth Cultivator; soil amendments and compost if adding and bring to work area. Bed Preparation Rake, Tilther and 3-Tooth Cultivator, Seedbed Roller, and Row Markers can be sourced from Johnny’s Selected Seeds.
2. Using Bed Preparation Rake, rake all beds smooth and level by pushing rocks and larger soil clods into the pathways.
3. If adding soil amendments, measure out for each bed and mix into an empty bucket, then spread evenly over the surface of each bed.
4. Using the Tilther or a 3-Tooth Cultivator, tilth each bed, doing two or three passes, to evenly incorporate the amendments into the top 3-inches of soil.
5. If adding compost, spread evenly over surface of beds and follow with another couple of passes of tilthing.
6. If direct seeding, first use a Seedbed Roller to prepare a smooth, firm seed bed.
7. If transplanting, slide red plastic Row Markers on select teeth of the Bed Preparation Rake to mark rows or create a grid pattern.
Crop Selection and Tips to Maximize Production in High Tunnels:
1. Select crops appropriate for the season including heat-loving crops like tomatoes, cucumbers and peppers during the summer season, and cold-hardy greens like spinach and kale during the late fall/winter/early spring seasons.
2. Consider growing ‘cut-and-come-again’ or multiple harvest crops such as baby lettuce mixes and salad greens as opposed to lettuce heads; indeterminate tomatoes as opposed to determinate or bush varieties; spinach, which is first harvested at baby size leaf-by-leaf for multiple harvests as opposed to one complete harvest at maturity; kale, which is also harvested leaf-by-leaf multiple times for baby leaf or bunches as opposed to one single harvest of a broccoli head at maturity.
3. Choose varieties which have been bred and selected to perform best in the growing conditions of a high tunnel or greenhouse, including a greenhouse-specific lettuce mix and parthenocarpic or self-fertilizing varieties of crops.
4. Always consider the vertical growing space in a high tunnel and grow crops which can be pruned and trellised such as indeterminate tomatoes and cucumbers.
5. Densely seed or transplant multiple rows of salad mixes, greens, carrots, radishes and other quick growing crops.
6. Consider multiple succession plantings of various crops throughout a season.
7. After the final harvest of a crop, avoid leaving the beds bare for longer than necessary. After bed preparation, seed or transplant whenever an empty growing space becomes available.
8. Closer plant spacing and multiple succession plantings within a season require frequent applications of compost and soil amendments.
9. Perform annual soil tests to monitor soil health and fertility.
10. Keep good records and experiment!