Answer: I think you are asking about the so called flowering cabbage (also called ornamental kale) with decorative coloring and leaf textures. You can purchase seed to start them yourself, (Burpee for instance offers seed) however it can be difficult to get the seed to germinate during the hot summer months. For this reason most gardeners purchase the plants in the fall for planting as cool season bedding plants. They tolerate frosts but do not survive the winter.
As with any cabbage or kale, they do best in a sunny spot with rich organic soil that is evenly moist yet well drained. Adding compost to the soil and using an organic mulch will be helpful. As far as fertilizer, you could use a general purpose granular fertilizer such as 10-10-10 per the label directions at planting time.
I hope this helps.
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