I will have roughly 90 in ground trees under low tunnels within the week. I put up the bare bones of each low tunnel the other day and now I am just waiting on the plastic to arrive. Low tunnels are frequently used for low growing crops usually covered with plastic, mesh or netting. Because I subscribe to a dense planting system and use the chop and cover method of winter protection, this seems like a great way to increase the soil temperature of my figs in the spring. This should net me quite a bit of GDD's. I think a safe estimate is to expect a large number of trees to ripen by August 1st. I'll have a video out soon on the specifics, but with these low tunnels I am thinking potted figs are mostly obsolete.
For a few reasons:
1. Low tunnels are affordable. I spent $250 on roughly 500 sq ft of low tunnels. That one time cost is nothing in comparison to the cost of containers, soil, fertilizer and water all season. With in ground trees, all I'm doing at this location is digging a hole, planting and walking away. They receive no food or water. They'll only receive free heat units from the GH plastic and additional tarps (another one time cost) for insulation & winter protection during the winter months.
2. Growing in ground is a lot less work in general. Think about not having to do the fig shuffle every year. Low tunnels are also easy to set up and easy to take down. I realize without photos it's a bit difficult to picture the exact design, but the design I went with on these low tunnels is not permanent. It's basically 1/2 inch PVC over top of rebar with 6 mil plastic thrown over top snugly clipped onto the PVC.
3. As I said above the GDD difference will be massive. Normally my in ground trees are about 2 weeks behind the potted trees (that receive no headstart) in production due to cooler soil temperatures in the spring. It does even out because in the fall the in ground trees have a 2 week longer season due to warmer soil temperatures. However, with these low tunnels I would expect that the in ground trees will wake up 30 days earlier on average than the potted trees that receive no headstart from my greenhouse. This is assuming a March 15th bud break vs an April 15th bud break. This will of course result in more fruits, earlier fruits and therefore higher quality fruits. And lets not forget about all that added heat the tunnels will provide compared to having a potted tree on the patio under no plastic.
How I am making this work efficiently:
1. I'm still playing around with the optimal spacing, but I densely space my trees 1.5, 2 & 3 feet apart. Under a 6 ft wide by 3 ft high low tunnel, you can fit at the very least 2 rows of figs with a 3 ft spacing. 3 rows with a 2 ft spacing.
2. The low tunnels again are not permanent and will be taken down sometime I imagine in June. At this time most trees will be outgrowing the tops of the tunnels and it will be warm enough to make the additional heat unnecessary and probably unwanted. This also makes your tunnels not as much of an eyesore for the duration of the growing season.
3. The tunnels will be set back up again during dormancy as a form of winter protection. Simply by throwing a tarp over top and adding some straw below, will guarantee survival. And because I cut my trees back each fall to 6-12 inches, these trees could be considered a "low growing crop" suitable for low tunnels. They're more size controlled this way.
A video is to come on this topic on Thursday. Stay tuned for that!