Dandelions are not commonly cultivated, in fact they are more commonly sought out for destruction rather than cultivation.
In the lexicon of the average gardener they are invasive weeds. However they can be very useful, tasty, nutritious and healthy. Dandelions are more nutritious than most of the more commonly devoured fruits and vegetables.
Dandelion greens are rich in phosphorus, potassium, calcium, vitamin C, iron, magnesium, thiamine, beta carotene and are high in fiber. It is claimed that dandelions are beneficial to your digestion, liver and kidneys and help to reduce cholesterol.
The greens are a substitute for spinach and can also be prepared similar to collard or turnip greens. The roots can be used as a coffee substitute.Dandelion Blossoms are used to make tasty Dandelion Tea and Dandelion Jelly.
The dandelion that most know as an invasive weed is Common Dandelion. Common dandelion has a tendency to be somewhat bitter if not grown or prepared properly. There are thousands of varieties of dandelions available, some are tastier or easier to grow than others. Many have a more subtle taste.
Other than the common dandelions there are also White and Pink Dandelions which lend themselves more to aesthetics than culinary appeal. Other dandelions such as French Dandelion are grown primarily for their greens and Arlington Dandelion which is much broader leafed than others. 'Italian Dandelion' is not actually a dandelion, but a type of chicory.
Dandelions are one of the oldest and hardiest plant species there is. It'll grow just about anywhere, regardless of soil conditions. It fares well in richer soil with above average moisture. It does best in full sun, but you don't really want it doing its best, at that point it becomes an invasive nuisance - you want to hold it back a tad - partial shade is best in this respect.
Plant dandelion seeds directly in the garden in early to mid spring. Soil should be well-drained and at the very least moderately fertile. Plant about 1/4 inch deep in either single rows or blocks. Optimal spacing is 6 - 8 inches.
Dandelions can also be intermingled in your herb garden, but it's not really advisable due to their invasive tendencies. I prefer to mono-crop them in a small patch to the side. Some people grow them in containers.
Dandelions are perennials, so long as the root remains in the ground the plant will keep coming back. This is good in the sense that you are ensured a continual supply, and bad in the sense that, as most already know, dandelions are highly invasive and can easily over grow their boundaries. They need to be kept in check. Preventing them from going to seed is helpful in this respect. But the roots also contribute to the perpetuation of this species, even root fragments can produce another plant.
To harvest a less bitter leaf, dandelions should be grown in partial shade. Sunlight helps the plant concentrate the compounds which cause its bitter taste, shading the plants blanches the leaves somewhat and will result in a less bitter leaf.
Prior to harvest, for several days cover the plants with a tarp or opaque fabric or whatever you have available, to deny them sunlight and further blanch out some of the bitterness. Harvesting the dandelion leaves when they are still young and tender will also lead to a less bitter culinary experience.
The shading of course only effects the greens, many people that grow dandelion do so for the blossoms , which are used to make tea and jelly. That being the case the greens are only an added benefit.
Blossoms should be bright yellow and young when harvested. Use them fresh, they don't store well, and dried they are close to useless. Be sure to remove all of the stem, it is very bitter and could easily ruin your entire batch.
If you plan on harvesting wild dandelions, be sure they are pesticide free - particularly for the blossoms, as toxins will accumulate there. Also avoid harvesting from any lawns that have been treated with chemical fertilizers, herbicides or pesticides. Dandelions may interfere with anti-diabetic medications, diuretics and some antibiotics.