The Benefits of Growing Mustard

16 August 2013, written by Barbara Pleasant

My fall garden is always bursting with greens, many of which are sharp-flavored mustards. Along with a little plot of mustard greens grown for use in the kitchen, I also use mustard as a late-season cover crop to suppress weeds and soil-borne diseases. Fast and easy to grow, mustard dresses up the fall garden with its frilly or colorful leaves. Mustard is always best as a fall crop, unless you want to grow seeds for grinding into spicy condiments. Growing mustard for seeds is best done in spring, because lengthening days trigger mustard plants to produce flowers.

Growing Mustard Greens

Technically, many popular Asian greens including mizuna and tatsoi are mustards, but varieties with broader leaves are synonymous with garden mustard. The ‘Southern Giant’ or ‘Green Wave’ mustard varieties are popular for their beautifully curled leaves, while ‘Florida Broadleaf’ has a strong track record of out-producing other mustard varieties grown for greens. And then there are the red mustards like ‘Red Giant’ and ‘Osaka Purple’, which are among the best edible ornamentals for the fall garden.

Mustard seed germination is fast and sure, so you can simply scatter the seeds over a renovated bed and then pat them in with your hand or the back of a rake. Within two weeks the planted area will be transformed into a sea of green, with very few weeds. I thin plants being grown for greens to a hand’s distance apart, and use the young greens pulled while thinning in stir-fries if they pass my taste test. Mustard greens that grow in warm weather usually have very strong flavor, which gentles down considerably as nights become longer and cooler in the fall. Fortunately, mustard plants are very willing to regrow should you opt to lop off and compost huge handfuls of summer-grown mustard greens. Within two weeks, a flush of tender new leaves will emerge from the plants’ centers.

Mustard greens have no problem with light frosts, but temperatures below 20°F (-7°C) usually kill plants back to the ground. Before this happens, I chop down the old plants and mix the chopped roots and greens into the soil, because rotting mustard tissues suppress nematodes and several common soil diseases. If this is the main benefit you want from mustard, simply grow your mustard as a cover crop.

Growing Mustard as a Cover Crop

A few weeks ago, one of the last things I did before leaving on vacation was to sow mustard in the beds where I had just harvested spring carrots and early potatoes. Less than a month later the beds are wall-to-wall mustard greens, with hardly a weed in sight. When sown in late summer, mustard grows so vigorously that weeds are smothered into submission.

Rather than eat all those mustard greens, I will chop them up using a sharp lawn edger, and then quickly turn them under using a digging fork. Numerous studies have shown that live mustard plant tissues, both seeds and roots, contain compounds that work as soil biofumigants by killing nematodes and pathogenic fungi. Reaping this benefit requires handling mustard like a green manure, because the beneficial compounds are released within hours after the plants are chopped down. But if you wait two weeks after turning under chopped mustard and then plant lettuce, you can expect a very productive crop with very few weeds.

Potato and vegetable farmers have begun using special mustard varieties as part of their rotation practices to suppress weeds and diseases. The method involves planting selected strains of mustard bred to produce high levels of glucosinolates in spring, and quickly chopping them up and turning them under in summer, when they reach full bloom. Used this way, mustard has a cleansing effect on soils that are carrying heavy pathogen loads. Mustard varieties to try for this purpose include Caliente, IdaGold and Kodiak.

Growing Mustard Seeds

Adventuresome garden cooks who want to experience natural spices at their best may want to grow mustard seeds, which have endless uses in the kitchen. You can toast and crack them for a crunchy, big-flavor garnish, grind a few with mortar and pestle to season sauces, or soak them in water for a day before blending with olive oil, vinegar and various other spices to make your own mustard.

Recipes may call for yellow, brown, or black mustard seeds. Seeds produced by most varieties of good-tasting mustard greens are mild-flavored yellow mustard seeds, just like the ones sold for pickling. The cover crop variety mixtures named above yield spicier brown seeds. Black mustard seeds (similar to brown ones) are popular in India and often can be found where fine spices are sold. In any color, edible mustard seeds are dried at low temperatures to preserve their flavor compounds, so they are often viable when planted in the garden. To grow your own mustard seeds for eating, simply grow a few nice plants in spring, and stake them if necessary when they bloom and set seeds. When the seed pods dry to tan in midsummer, gather them in a paper bag and let them dry until crispy, then crunch thoroughly with your hands and gather the seeds that fall to the bottom.

By Barbara Pleasant