Asian greens such as mizuna and mibuna are the perfect additions for your polytunnel, ideal for salads and stir fries. Mizuna has cut and come again leaves with a distinctive peppery, cabbage flavour and mibuna, slightly stronger tasting, as a mustard-like kick. Both can be perfect for addition to a a more mild selection of leaves in salads or quickly cooked dishes.
Mizuna and mibuna both offer good value as cut and come again crops and can be planted on a regular succession for a year-round supply. Winter crops may need a little extra protection from the cold in more northerly reaches of the UK but should be a valuable green food source when few other plants will be available. Sow between March and August, directly into the soil in the polytunnel where they are to grow. You can also sow seeds indoors in February for an earlier crop, hardening them off before planting out where they are to grow.
Thin seedlings to around 15cm apart for plants that are to be used when they are young. Allow a slightly wider spacing, perhaps around 30cm, for plants that will not be harvested until they mature fully.
Both mizuna and mibuna are extremely easy to grow. They are tolerant of cooler, wetter conditions and can cope with a wide range of soil types. However, do bear in mind when growing them in your polytunnel that they do dislike extreme heat and so will usually grow best when given some shade in the summer months. For this reason, they are best grown as an understorey beneath other plants in the hottest months of the year.
These leafy plants will benefit from a soil rich in organic matter and will thrive when mulched with a high nitrogen mulch over the spring and summer. Water well throughout the year and take care to prevent the soil surrounding the plants from drying out.
These quick crops can be harvested from as little as three weeks after the seeds are sown and larger plants can be harvested up to five times before they bolt and go to seed. (Seeds can then be fairly easily collected for use the following year.) It is best to remove a few leaves from several plants rather than depleting one plant too dramatically as this will prevent weakening of any one individual plant.