Mustard is another leafy green to add to your salad, giving you a tasty variation to normal greens. Mustards can get quite large, so be prepared to give it some space to grow.
Prepare the planting site by tilling down 6-12” to loosen any compacted soil. Incorporate 2-4” of compost or manure prior to seeding or add a balanced organic fertilizer.
Sow mustard seeds directly into the garden 2-3 weeks prior to the last expected frost. Mustard can grow well in cooler weather, but too many frosts can cause the plants to bolt. You can also start seeds inside 4-6 weeks before the last frost and then transplant the young seedlings no earlier than 3 weeks before the last frost.
Seeds can easily be scattered and gently pressed into the soil, or can be individually planted 1/2” deep every 2-3”. Once the seedlings are about 2-4” tall, thin to 4-8” apart. Thinned out plants can be eaten. Side dress with a nitrogen-rich fertilizer midway through growth. Mustard does very well next to other leafy greens, like spinach and lettuce, but can share the same pests, such as flea beetles, snails, caterpillars, and grasshoppers. Peas are a good companion plant, as they add nitrogen to the soil, which will increase mustard foliage. Water mustard with 1” of water each week, keeping the moisture even. Laying a 2- to 3-inch layer of hardwood mulch will aid in water retention and regulate soil temperatures.
Mustard can be harvested as early as three weeks from planting for baby greens, or wait the full seven weeks to harvest the mature outer leaves. Leave the rest of the plant to continue growing or cut the mustard “head” off at soil level to harvest the entire plant. Harvests should be done before the weather gets too hot and the plant bolts. Once this occurs, mustard flavor can become strong and the leaves can be tough. However, mustard seed can be used as both a spice and to make the popular condiment. For the best flavored seeds, you want the plant to complete as much of its life cycle as possible and to flower as it normally would. Once the plant puts on flowers, leave them in place to develop seed pods. You don’t want to harvest the pods until they turn brown, but if you wait too long, the pods can burst open and you will lose the seeds (and have volunteer mustard plants). Once the pods turn brown, cut the pods off of the plant and into a brown paper bag. Allow them to dry completely for about a week (paper is better for this than plastic), then give the bag a few shakes to separate the seeds from the pods. Mustard seeds as spices can be used fresh, or can be dried and stored, or you can save some of the seeds for planting again in the fall!