Onions are valuable culinary vegetables, and also have medicinal value.
The color of an onion gives you some insight into it's properties. The white onions are the strongest, followed by yellow, with red or purple being the mildest-flavored types. The length of day affects the growth of some onions, so when buying onion sets or seeds, be sure to find out whether the onion in question is appropriate for your area. Some do better in the south and others do better in the north - and some do well anywhere.
Onions can be started from seed or from sets. Sets are slightly more expensive but give a much quicker result thanseeds. In the south, they can be planted in the fall for a spring harvest, but in the north, early spring is the best time to plant. When planting sets, be sure that you plant the bulblet with the pointed end up.
Onions prefer rich, well-drained, moist soil. They are an easy plant to grow and require little maintenance other than weeding once planted. Harvest young scallions at any time. To harvest mature bulbs, wait until the tops begin to yellow. Knock the plants down and leave them there for a couple of days. Then carefully pull the plant. Move harvested bulbs to a dry area and set them on a screen for a few days for drying. They can then be braided together or placed in mesh bags for storage. They keep well if stored properly, and do not keep well in the refrigerator.
Onions have been used for their medicinal properties for centuries. They have anti-bacterial and anti-fungal properties, and a paste or ointment made out of onion is said to prevent infection in wounds and burns. Another use externally for age spots, warts, or freckles is to mix onion juice with vinegar and rub on the affected areas.
Onions and all the other members of the Allium family are thought to have some impact on high cholesterol and blood pressure. An onion tea can be made and used daily, but I'm not sure how that would taste. The prudent thing for blood pressure and high cholesterol is probably to just include onions in your diet at every opportunity. Unfortunately, the down side to this is that onion compounds travel through the body when ingested and it takes time to process them out through sweat or breathing. Just brushing the teeth doesn't make the odor go away. So, you'll live to a ripe old age, and nobody will want to be around you...