A polytunnel can be perfect for growing a huge range of different crops. But one of the challenges of growing in a confined space like a polytunnel is creating the different growing zones. We need different growing zones to provide the different growing conditions necessary for diverse crops. In a polytunnel, we often wish to grow a wide range of crops. And those different crops do not always require the same soil and environmental conditions. In this article, we’ll delve into how you can set up your polytunnel to create different areas suited to growing diverse crops.
Creating Raised Beds With Different Growing Mediums
One way to create different growing zones is to establish different raised beds with different growing mediums.
For example, you might create one bed with sand/ grit incorporated so as to create conditions suitable for plants that prefer a free-draining soil. (If you have a heavy clay soil, or a very stoney soil, this could be your best bet for growing carrots and certain other root crops.)
You might also create a raised bed with ericaceous compost – to grow acid-loving plants in an area with more alkaline soil. Or fill a raised bed with a more neutral/ alkaline growing medium in an area where the soil is acidic.
Amending the Soil Within Different Growing Zones
Another way to alter the pH or other characteristics of the soil is simply to amend the soil differently within different areas. One example of this might be adding lime to reduce incidence of club root in brassicas in areas of acidic soil.
You might also want to create a growing zone with, for example, greater content of calcium, or another soil nutrient. To grow specific plants that need plenty of calcium more successfully. Adding eggshells or milk powder to a specific growing area could do the trick. Ands this is just one of many examples.
Using Planting To Alter Immediate Environmental Conditions
It is important to remember that all the plants you choose will have a subtle but notable effect on the environmental conditions around them. You can use plants to alter the conditions in different growing zones within your polytunnel.
One simple example is using taller plants to provide shade, and alter the growing conditions for plants placed below. Plants could also provide ground cover to reduce soil moisture loss from around their neighbours.
But plants can also impact their environments in other ways. For example, nitrogen fixing plants may boost soil nitrogen, and benefit plants grown nearby.
Creating Hugelkultur Mounds or Herb Spirals – to Provide Different Conditions Within a Limited Space
We’ve already spoken about how you can use different raised beds to provide different growing conditions. But when you opt for hugelkultur mounds or herb spirals, you can provide a wider range of different conditions within a given space.
By creating 3D landscaping within your polytunnel, you can create shadier areas and sunnier ones, dryer and damper conditions. You can place individual plants in specific places in your mound or spiral to provide the ideal conditions for them.
Manipulating Watering With Distinct Irrigation Systems
Setting up an irrigation system in your polytunnel, rather than simply watering by hand can be a real time-saver. It can also allow you to make sure that each plant gets the water it needs. But it is also important to remember that you do not necessarily have to set up just one automated watering system to water all polytunnel plants at the same time.
You could also set up multiple systems, designed to water different areas of your polytunnel different amounts and at different frequencies. You could have an area of your polytunnel devoted to dry climate plants, and another devoted to more thirsty crops.
Altering Ventilation to Cool Certain Parts of the Polytunnel
By careful use of ventilation, and by thinking carefully about how you manage air flow through your polytunnel, you could also create a polytunnel in which some sections are cooler than others. Hard-features such as staging, trellises with climbing plants, and other tall plants could block or direct air flow to a degree.
And by opening ventilation on both sides of the tunnel, you could create a through breeze that will only affect certain plants and growing areas. The properties of air flow and ventilation can be manipulated to cool down certain parts of the polytunnel while keeping other areas that little bit warmer.
Creating Warmer Areas Within the Polytunnel
As well as making certain areas of the polytunnel a little cooler, you can make certain areas warmer too. There are a number of different ways that you can do so:
For example, you can:
Place cloches, row covers or mini polytunnels over certain growing areas or certain plants.
Using mulches to warm areas of soil (or keep them cool in summer).
Create a hot bed, and allow decomposing material to gently warm plants from below.
Add thermal mass to certain beds or growing areas, to make them stay a little warmer at night or in chilly weather.
Create a tunnel within the tunnel, and heat it with a solar electric heater, or another eco-friendly method of heating.
Changing Humidity Levels Within Certain Zones
Different plants also like different humidity levels. By watering hard surfaces within a certain zone (i.e. within a mini polytunnel within the larger one) you could create a much more humid environment for those plants that like it without affecting the plants grown in other zones.
But what if it is not just a small growing area that you want to alter the environment in? Is there a way to fully divide your polytunnel into larger, separate areas? The answer is yes. With a little work and effort, depending on exactly what you want to achieve, there are a couple of more elaborate steps you can take to fully partition your polytunnel.
Partitioning Growing Zones in a Polytunnel With Plants
If you want to create a partition that blocks some airflow, but allows for some interplay between the zones, you could consider creating a partition with plants. This will not actually be a full partition, but can allow you to have separate zones for different types of plants. Plants grown on a trellis, and tall plants to the sides of the polytunnel can help to keep one zone separated somewhat from the other.
One use of such a partition might be to alter ventilation, as described above. But another might be to create a section of your polytunnel for plants that like sun, and a second section (north of the trellis/ tall plants) to create a shade garden.
Creating Partitions Between Growing Zones With Plastic Sheeting
Finally, you could consider effectively turning one polytunnel into two (or more) distinct spaces. You could do so by hanging a barrier of plastic polytunnel cover material or other sheeting between the different zones. And taping it in place.
This could allow you to very effectively manage different zones at different temperatures and/or humidity levels. And to grow an even wider range of plants where you live. For example, you could heat one side of your polytunnel and use it to experiment with growing subtropical or tropical plants. You could keep the other side cooler for more traditional UK crops.
Have you set up your polytunnel to create different growing zones. Do you grow a wide range of different plants that like different conditions in your polytunnel? Share your experiences, tips and suggestions in the comments below.
Elizabeth Waddington is a writer and green living consultant living in Scotland. Permaculture and sustainability are at the heart of everything she does, from designing gardens and farms around the world, to inspiring and facilitating positive change for small companies and individuals.
She also works on her own property, where she grows fruit and vegetables, keeps chickens and is working on the eco-renovation of an old stone barn.
To get in touch, visit https://ewspconsultancy.com.