Daikon radishes are a type of oriental radish which is often grown as a winter crop. They are grown for culinary use, but can also be grown as a green manure or cover crop. Their deep, large roots effectively break up the soil structure, bringing better aeration and essentially cultivating your soil for you to a deep level. This can be especially beneficial in areas with heavy clay soil. They are a type of dynamic accumulator, and can work well alongside leguminous nitrogen fixers that are planted as a winter green manure – such as broad or field beans.
Daikon radishes sown in September will overwinter in your polytunnel. They are fully hardy and should survive the winter here in the UK in an unheated undercover growing space.
Growing Daikon Radishes as an Edible Crop
Raphanus sativus var. longipinnatus is mild in flavour, with a long, white root. It can be eaten raw or cooked. Sometimes, it is also known as Chinese radish. The name Daikon comes from its Japanese name and can be translated literally as ‘big root’. Eating daikon radishes is great for your health. These vegetables are low in calories, yet pack quite some nutritional punch.
Daikon radishes that are to be used for culinary use are usually harvested after a couple of months. Daikon radish roots can be sliced finely and eaten raw. They can also be boiled or roasted and used in a range of versatile ways in your kitchen. They are common ingredients in China, Japan and other Asian cultures, and are a key ingredient in kimchi, and they can also be used in other fermentation recipes.
The leaves can also be cooked and eaten. Don’t be put off by the texture of the raw leaves. Once cooked, these are similar to other green vegetables. And if you let the radishes set seed, you can also have an abundant – staggeringly abundant – supply of radish pods come spring.
Growing Daikon Radishes as a Winter Cover Crop
According to Masanobu Fukuoka, in his natural farming book, “One Straw Revolution”, the name for the wild ancestor of daikon translates as ” ‘the herb that soften’s one’s disposition’. There is a belief that it calms the body when served in steaming soups. Whether or not it does indeed soften the disposition, it certainly can reduce problems with hard soil. As Masanobu states in his book,
“if the soil is hard, grow Japanese radish first.”
Daikon radishes have been described as nature’s rototiller. In no dig gardens, especially those with harder or compacted soils, it breaks through soil layers, opening up channels for water and roots. But unlike using rototillers and other such equipment, or even simple garden tools, allowing plants like Daikon radishes to do this work for you also increase soil organic matter and helps you preserve and protect the precious soil ecosystem.
Daikon radishes also make a good winter cover crop because they are good at catching and storing last years nitrogen. In areas where they naturally die over winter, they release that nitrogen quickly in the spring for the plants grown in the area in the following season. In a UK polytunnel, they will not usually break down. But the material can be chopped and cropped to return the nutrients the plants contain to the system.
With their large leaves, daikon radishes also help keep the soil covered. They help to keep beds weed free over the colder months, and protect the soil surface, especially when used as part of mixed cover crops along with other species.
The seeds of Daikon radishes can be sown any time from July through to September, and there is another brief window of opportunity to sow them in late winter. If you are growing them for edible use, then the seeds should be sown around 2cm deep and 2cm apart.
If sowing as part of a cover crop, close spacing is desirable and though there are few hard and fast rules regarding spacing, you should aim for good distribution over areas where you would like them to break up the soil and provide their other ecosystem services.
When growing Daikon radishes for edible use, the primary job will be to thin out your seedlings to allow the remaining ones to grow to a decent size. Usually, you will aim for an ultimate spacing of around 10cm between plants.
Remember, the plants that you thin should not be thrown away. The smaller roots can still be eaten and should not be allowed to go to waste.
Water Requirements and Care
Daikon radishes will require watering in a polytunnel, but do not require excessive care. As long as sufficient water is provided you should find that you can grow daikon radishes very easily. You should find you can grow them without a lot of effort, whether you are growing them as edible crops or not.
Daikon radishes which are grown as edible crops should usually be ready to harvest within around two months. So sowing in September will likely mean that you can begin to reap the benefits of your work before Christmas. Though you can of course leave the radishes in the ground for longer. If you want to wait for larger roots, or to chop and drop in the spring.
Among the other things to sow and grow over winter in your polytunnel, daikon radishes can be an interesting and useful choice. So consider sowing some in September before the colder weather arrives.
Have you grown Daikon radishes in your own garden? Share your experiences, tips and comments with us 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.