Kale is one of the most worthwhile crops you can grow. It is easy, undemanding, tolerant of heat, drought, wet, cold, and poor soil. It can be eaten at the small leaf stage in salads, mid-size leaves are good steamed, and large leaves can be chopped and stir fried or put into stews. One especially good dish is lentil stew with leeks and kale. I eat the steamed flower buds which look like miniature heads of broccoli, and sprinkle the bright yellow flowers raw into salads. The seed pods are crunchy and tasty when young and I have even germinated kale seeds to eat as sprouts. Kale is one of the most nutritious vegetables you can grow. It contains iron, calcium, B vitamins, potassium, and a significant amount of vitamins C, A and K. It is full of organosulfur phytonutrients that recent research have shown to reduce the risk of cataracts, as well as cancers, especially colon and ovarian cancer.
I have planted kale in early spring, mid and late spring, and right up until late summer. In fact I don't plant kale anymore in my garden, I just let it self-seed. I have young kale seedlings coming up every time of the year except in the coldest part of winter. I generally have grown a very winter hardy kale called "Red Russian" which is by far my favorite, but have also grown another red kale called Ursa, and a green one called Siberian. These three all do very well for me on Vancouver Island, Canada. In even colder areas I suggest a more curly kale called Winterbor, and in areas where summers are extremely hot a new kale called Rainbow Lacinato is the slowest to bolt. Rainbow Lacinato is also the most colorful kale, with leaves of green, purple, and red. My kale is tender and sweet in all but the hottest months of the year. Although it is tastiest in cold weather after a light frost I have harvested kale even in mid-summer and by putting it in the freezer for a half hour or so it seems to lose some of it's strong summer flavor. After an extreme freeze I often lose a few leaves from my kale plants, but when the temperature warms up to anywhere above 0 the leaves start to regrow. In harsh winter areas I would try to overwinter fairly large plants, harvesting one or two large leaves at a time from under the snow.
Although kale will tolerate nearly any type of soil, for truly succulent plants try spreading a couple of inches of compost around the area you will be planting into. Many books specify a full sun location for kale, but I have found that mine does well protected from intense summer heat by the shade of a large ornamental plum tree. I merely scatter the seeds fairly thickly on the compost, then cover them lightly with more compost. When the seeds come up I begin to thin and use the thinnings to add flavor and nutrition to salads.
I keep thinning, and eating until the plants are about one foot apart. As the plants get bigger I begin to harvest a couple of lower leaves at a time. I leave the best plants alone to produce seeds. Usually my kale plants will not set flower until the following spring, but sometimes when the plants are under stress they will bolt to seed earlier. I find if the soil is extremely poor, if I have not kept up with the thinning, or if I have let the plants get way too dry it increases the risk of bolting. I generally eat the buds and flowers of any small plants along with the leaves, but larger plants I always leave alone so that they can continue to seed my garden. I often put additional compost around these larger mother plants, and sometime have to tie up the leaves a bit so that they don't take up quite as much space in the garden.
The varieties I grow are all open pollinated, not hybrids, so I can continue to select the best plants from each batch of kale to save for seed. Over the years I have selected the plants that have the best heat and cold tolerance, and my kale crop has improved every year. Homegrown kale bears little resemblance in taste or texture to store bought or restaurant kale served as a garnish. Kale does not keep well at all, even a short time between harvest and dinner can toughen and discolor it. If your only experience with kale has been purchased do yourself a favor and plant a pack of kale seeds this year. I can assure you that if you like eating greens at all that you are in for a real treat