How I Maximize the Space in My Growing Tunnel
A number of strategies help make the most of the space in my polytunnel, and increase my annual yield.
A polytunnel structure like the author's, in a cottage garden near Aberdeen.
Stanley Howe / Geograph
I have a growing tunnel, just 10-feet wide and 20-feet long. But I manage to grow a lot more food inside it than you might think possible.
The first and most important step in maximizing the space is making sure that I use it all year round. I live in Scotland. Temperatures can occasionally dip below -5 C (23 F) in winter, but this is not common. Summers are quite cool. We have a moderately short growing season. Last frosts are typically in April, and first frosts are typically around mid-October.
My main reason for having a polytunnel is to make it possible to grow a wider range of crops over the winter months. But it is also important in summer, when it makes it much easier to grow warm-season crops like tomatoes, peppers, and corn.
In spring, I often sow interim early-season crops – peas, broad beans, first early potatoes, lettuce, and other salad crops – which will be ready to harvest in June to make space for the warm-season summer crops. After midsummer, I sow brassicas and other leafy greens which can overwinter in the polytunnel, accompanied by alliums for overwintering in the fall. Every time a gap opens up, there is something new to transplant into the space.
Year-round growing means taking care to maintain fertility over time. And also thinking about crop rotation. I rotate key crop families on a three-year rotation. I also mulch and use organic liquid feeds, as well as nitrogen-fixing crops, to maintain nutrient levels.
As well as thinking about what I sow and when I plant, making the most of the space inside the tunnel has also involved some careful planning in terms of the layout.
I have two long beds, one down each side of the tunnel, and a rectangular bed down the center. This creates two thin paths, with small areas at either end of the tunnel where there are doors. But I also utilize the pathways through the year by placing planting containers along them that I can step over to access all the growing areas.
At the north end of the central bed, I have a trellis structure (made from reclaimed wood and fencing wire) leaning against one of the crop bars. Two grapevines climb the south side of this structure, and other plants can also be trained onto it from below. On the rear side, I have used milk containers to make a vertical garden, where leafy crops grow. I use these for some seedlings in the colder months and grow spinach and other leafy greens in the shade during the summer.
Above the central bed, I also created a hanging shelf with reclaimed wood and a sheet of clear plastic leftover from the creation of the tunnel's cover. This hanging shelf is used for seedlings and hardening off transplants from indoors. And it can be raised or lowered as required throughout the year. I also have two hanging baskets that are used as additional growing space.
Finally, it is worth mentioning that I also try to make the most of the space in my growing tunnel by creating polycultures of plants.
In a polyculture approach to gardening, multiple crops are grown in the same space in imitation of the diversity of natural ecosystems.
Companion planting is key. I think about which plants will grow well together, without competing too much. And think about how certain plants may be beneficial to others by, for example, creating shade or ground cover, dynamically accumulating nutrients (before being chopped and dropped), attracting pollinators or predatory insects, or helping in organic pest control.
Rather than just growing tomatoes in one bed, and brassicas in another, I will combine crops, and also add in other herbs, flowers, etc. for additional yields. For example, I grow basil, lettuce and other leafy greens, and spring onions alongside tomatoes. I grow peas or beans between brassicas and allow chickweed to grow as ground cover below them.
These are but some ideas for how to maximize yields in a growing tunnel. With careful thought and planning, one can garden year-round and grow a surprising amount of food in a relatively small space.