Crop rotation is one of the things that can be rather confusing if you are new to gardening. But it is not quite as complicated and complex as you may imagine. Simply put, crop rotation is just the idea that you avoid growing certain plants in the same growing area for multiple years. Instead, you ‘rotate’ them around a series of different beds. Here are some top tips for crop rotation to help you make the most of your polytunnel garden:
1. Make Sure You Understand the Benefits of Crop Rotation
First and foremost, it is important to understand why crop rotation can be a good idea. Crop rotation can have a range of benefits. It can:
Help spread nutrients where they are needed around your garden.
Protect the soil and avoid excessive depletion of nutrients.
Reduce the chances of a build up of disease in the soil.
Reduce the incidence of pest problems (especially pests which overwinter in the soil).
And so, keep your plants healthier.
2. Understand that You Don’t Need To Rotate All Crops
While crop rotation can be beneficial, however, it is important to understand that it is not essential for all crops. Crop rotation is not something that needs to be adhered to strictly. And it can often be a good idea to take a somewhat more relaxed approach.
Some plants don’t need to a rotated to different growing areas each year. Some will do absolutely fine when grown in the same location year after year. Perennial plants don’t need to be included in a crop rotation scheme, of course. They can usually stay where they are with few problems year after year. And even certain annual crops can be grown in the same area over multiple years.
3. Recognise that You Can Still Use Companion Planting
Another important thing to understand about crop rotation is that you can still companion plant. Even when you have worked out a crop rotation scheme for certain main annual plant families, you can still grow other companion plants alongside them to increase your yields and improve results.
Creating polycultures in your polytunnel is a great strategy, and it is not incompatible with a crop rotation approach. The crops you are rotating can still benefit from companion crops in a wide range of different ways. For example, companion plants can:
Improve environmental conditions for plants grown close by.
Or other beneficial insects such as those which eat pest species.
Repel, confuse or distract a range of common pests.
Provide additional yields, and allow you to make the most of time and space.
4. Identify Plant Families That Can Suffer Without Crop Rotation
Working out how to integrate the two useful approaches of crop rotation and companion planting involves careful thought. But the best place to begin is by identifying the different plant families that can suffer when crop rotation is not implemented.
A crop rotation scheme is usually based around making sure you don’t grow these plant families in the same beds or growing areas for more than one year:
Solanaceae (the Nightshade family): potatoes, tomatoes, peppers, aubergines etc..
Brassicas: broccoli, cauliflower, kale, kohlrabi etc…
Alliums (the onion family) and root crops: carrots, parsnips, beetroots, etc…
If members of the Nightshade family are grown in the same bed for more than one year, this may increase the likelihood of developing problems with fungal diseases such as blight.
If brassicas are grown in the same bed year after year, they will tend to deplete soil nitrogen, and can develop problems such as root rot.
Onions and certain root crops like carrots can also be more prone to disease if they are grown in the same bed year after year.
5. But Recognise That There Are Exceptions To Be Made in Crop Rotation
Most crop rotation schemes will be based around moving these three key groups of plants. But it is worth noting that there are certain exceptions to be made. For example, while you will want to move most annual brassicas around, you can consider growing certain perennial brassicas in the same place over a number of years without ill effect.
There are also perennial onions that can be grown, usually issue free, in with other perennial plants, either in a polytunnel or elsewhere in your garden. You won’t have to move these around either.
6. Aim For a Four Year Crop Rotation For Certain Key Plant Families
It is a good idea to be quite flexible when it comes to crop rotation. You can adapt and alter your plans over time. But it is a good idea to aim for a four year crop rotation, which includes those three plant families mentioned above, along with a fourth category – legumes such as peas or beans.
An example four year crop rotation plan for a polytunnel (used for year-round growing) might look as follows:
Bed 1: Broad beans or peas, followed by brassicas.
2: Brassicas, followed by tomatoes or other nightshade plants.
3: Quick spring crops (lettuce etc) followed by green beans, runner beans or other legumes.
4: Onions and root crops.
Bed 1: Brassicas, followed by tomatoes or other nightshade plants.
2: Quick spring crops (lettuce etc) followed by green beans, runner beans or other legumes.
3: Onions and root crops.
4: Broad beans or peas, followed by brassicas.
Bed 1: Quick spring crops (lettuce etc) followed by green beans, runner beans or other legumes.
2: Onions and root crops.
3: Broad beans or peas, followed by brassicas.
4: Brassicas, followed by tomatoes or other nightshade plants.
Bed 1: Onions and root crops.
2: Broad beans or peas, followed by brassicas.
3: Brassicas, followed by tomatoes or other nightshade plants.
4: Quick spring crops (lettuce etc) followed by green beans, runner beans or other legumes.
Of course, this is just one example of a potential scheme. And of course you can also include plenty of other plants alongside these key plant families.
7. Rotate Nitrogen Fixers in Crop Rotation To Spread the Benefits Around
One of the most important things in a crop rotation scheme are the nitrogen fixing legumes. It is vital to make sure that you include legumes and other nitrogen fixers throughout your garden. These peas, beans etc. work with beneficial bacteria in their roots to replenish nitrogen – a key plant nutrient – in the soil.
8. Consider Following Nitrogen Fixers With Nitrogen-Hungry Brassicas
One strategy that I would recommend is following nitrogen fixing legumes with nitrogen-hungry brassicas (and other leafy crops). This will help to avoid the depletion of nitrogen in the soil and can help keep your garden in balance.
9. Consider Following Potatoes With Onions and Root Crops
In the example given above, I showed how you might integrate tomatoes and other warmer weather nightshade family plants in your polytunnel crop rotation scheme. But what about potatoes? If you are growing potatoes in your polytunnel, I would recommend following these with your onions and root crops. The potato cultivation helps to break up and aerate the soil, which will benefit these plants and help them thrive.
10. Don’t Leave Beds Bare if The Next Crop Is Not Going in Right Away
In a polytunnel, it is important to remember that you will not just be restricted to summer growing. You can grow year round. This can sometimes make it more challenging to work out the best crop rotation scheme. But if you plan well, you should never have bare growing areas. If you work out a good plan, but your next main crop can’t go in right away, you can often use green manures or cover crops to good advantage. For example, you might have a leguminous cover crop, or a green manure like mustard, for example, to improve soil structure…
These are just a few tips to help you develop a crop rotation plan for your polytunnel. Do you have any of your own tips to share? Let us know 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.