WATERCRESS
Watercress is a fast-growing plant that has a nice biting taste and can therefore add a nice sting to your salads or sandwiches. The nice thing is that you can grow watercress at home, either in your garden - to fully grown plants, or in your kitchen - as watercress sprouts (see the picture). Historically, watercress has been known as a healthy food or super food, grown in spring waters in England since two centuries. It has been one of the basic ingredients in diets of the lower middle class and poorer people, since it was relatively cheap or widely available in the country, and some people didn't even have money to buy some bread. So, watercress became a hit among these people, but nowadays it seems to be somehow forgotten. Watercress was also eaten already in the ancient Greece, where it was considered to be an intellect-enhancing plant, and it was also used for medical purposes. People in these ages of history also ate it to prevent baldness, and to get rid of hang-overs, just to name a few funny examples.
If you wish to grow watercress in your garden you need to have a very moist soil, or simply keep it moist by watering it as necessary. Otherwise there's really not much to it, just plant the seeds and wait for the plants to grow. It is a very easy plant to master, and it likes water, especially slightly alkaline water. Watercress can grow as high as your knees or even up to your hips. Just make sure to harvest it before it starts to generate flowers, because then it will become bitter. Also after harvest, you need to consume it at once for the best taste experience. Watercress is not very good for long-time storage, which is probably why you never see it in the shops (although it recently came out packages that preserve it better, but this is still not the optimal way to have your watercress). So, either gardening or sprouts (also available in the shops) will make your day. Other options are not really options, but way beyond second best.
The usual season for watercress is the spring. Watercress can be combined with a number of foods, if you want to make it the main ingredient in a dish (e.g. a watercress soup). The classical additions are parsley and mustard, or endives. To season it you can use thyme, or walnuts, or maybe some oregano. Since this is a plant, commonly used in salads and such, a nice vinaigrette also suits with watercress. Otherwise, when it comes to techniques of cooking the plant, it can be puréed and used in soups, and it is most often eaten raw.
From the nutritional point of view, watercress has been said to have good qualities to prevent cancerous changes in our bodies, mainly due to a high content of phytochemicals and antioxidants. It also is a good source of vitamin A and C, and the minerals iron, folic acid, and calcium.