You can sow Mustard direct in the soil or in module trays for later transplanting. I generally sow 5-6 seeds in each module in a module tray and plant out each little cluster of plants 3-4 weeks later. The best results are from a small regular sowing every 3-4 weeks from February until September, but the late spring and summer sowings are often inclined to bolt. It really comes in to its own in the autumn / winter. I do a larger sowing in September to last through the winter and early spring.
As with most of the oriental greens family of veg, mustard is versatile and there are a few different ways to grow it.
Winter outdoor sowings might need a fleece cover. Water in very dry weather or if growing in a polytunnel or greenhouse.
At some times of the year you can harvest sparingly as early as 4 weeks after sowing, particularly when you are growing for ‘cut and come again’ small leaves. As the name suggest with a ‘cut and come’ again crop you can cut it back with a scissors and expect multiple crops of delicious leaves. You can either harvest individual leaves by hand-picking, or cut with a scissors down to about 5cm from the soil.
It’s a brassica so in theory it should be included in your brassica rotation and can be prone to all diseases that brassicas get - in practice you don’t get many problems with it at all. Slugs do like a nibble on the leaves.