Mustard is a member of the Brassica family - closely related to things like cabbage, cauliflower, broccoli and Brussels sprouts. Also related are Asian greens like Bok Choy, Tatsoi, Mizuna, Choy Sum, etc, some of which have a mild mustardy flavour.

Mustard leaves are yellowish to medium green and fairly wide. When they are mature, the plants are large, loose and open. The White Mustard, (B. alba), is a common weed. The Black Mustard, (B. nigra), is a tall annual, that is grown commercially for its seeds, which are dried and ground to make the familiar condiment mustard. It grows up to 2 metres high. The plant has coarse leaves and branches of yellow flowers, which are followed by sickle-shaped pods of seeds. Brown mustard (B. juncea) grows to about 1.5 metres and is the variety most frequently grown. It has a mass of small, four-petalled yellow flowers that form a dense carpet when allowed to self-seed.

Sprouts are excellent in sandwiches and salads. The greens have a slight peppery taste and may be cooked alone or with other greens. They may be chopped for salads when very small. Flowers and young seed pods are used in salads. Seeds are crushed and mixed to a paste with cold water (not hot) to make the familiar condiment which is served with meats, or added to sauces and salad dressings, egg and cheese dishes. Mustard seeds are also used as a pickling spice, alone or with other spices.

Medicinal Uses: Add mustard powder to hot water and use as a soak for sore and aching feet and muscles. Relieves muscular spasms, pins and needles, symptoms of colds and flu and bronchitis. If mixed with water to a runny paste, it can be taken to induce vomiting after ingestion of poisons in an emergency when no alternatives are available. Whole plant is a powerful antiseptic and disinfectant. As a tea, it will stimulate urination and may bring on a delayed menstrual period. It also stimulates the circulation and will aid chilblains.

Mustard is most commonly used as a poultice which can be made by mixing 10g freshly ground mustard seeds with warm water (at about 45C) to form a thick paste. This is spread on a piece of cloth the size of the body area that is to be covered. To stop the paste sticking to the skin, lay a dampened gauze on the skin. Apply the cloth and remove after l minute. The skin may be reddened by this treatment which can be eased by applying olive oil afterward. Or for internal use, pour 1 cup boiling water onto 1 teaspoon mustard powder and leave to infuse for 5 minutes. Take 3 taimes per day. As a footbath, make an infusion with 1 tablespoon bruised seeds and 1 litre boiling water.

Warning: A mustard poultice (plaster) can easily burn and blister the skin. Do not use on children, and best left to someone with trained in the procedure.

Another warning: Do not eat any plant unless and until you have correctly identified it with 100% certainty. 'Some kind of mustard' sounds far too vague for me to be satisfied that it is, indeed, mustard, regardless of the taste and appearance! It may well be mustard - and then again it may well NOT be.

You can usually start your own mustard plants very easily using seed - either seed packaged for propagating, or seed purchased in the spice section of your supermarket. They sprout quite quickly, and can be used as sprouts. At least this way, you can be sure you've got the right plant!

Around these here parts, the Japanese like the tender flowers and shoots, the Chinese like the leaves.... and they go out to the fields and harvest them... free food! :oD
I know this because my Japanese BF tells me stories of doing that as a kid.

As far as I know, all brassica are edible. You recognize them by their flowers, being crucifers, i.e. the flowers have 4 petals in the shape of a cross. Most are yellow, but a few wild ones, commonly recognized as weeds are white. I have always eaten all of them, and children love to eat the weeds as well. Some are slightly bitter because they are so strong.

The cultivated ones which are grown in gardens will deteriorate from year to year from being cross-pollinated with others. I bought a seed package of "mustard greens" in Texas about 25 years ago where it is used like spinach and is very popular. It has huge leaves, but year after year, those leaves have been getting smaller, because there are too many other mustards around with which it has been cross-pollinated. It is the best-tasting mustard plant I have and I use the leaves and flowers in salads. Canola, on the other hand, has very small leaves, because it is grown for the seed oil.

The best-known crucifers are probably radishes, and I use their leaves, flowers, and seedpods the same way if the roots have gone woody in our hot summers.

Thank you! Now that I know that these are probably edible, I'll take a plant sample to a couple of nurseries. Is the "hot" part of mustard caused by Capsaicin, as it is in most peppers?

You can also eat alyssums, which are related and have the
same flavor.

I'm pretty sure all brassicas are edible? I have garden cress growing and boy does it pack a punch! :)

I just learned that sea rocket (Cakile edentula), a succulent, is also in the mustard family. We like to nibble at it when at the beach. It gets hot/pungent when mature.