What are the three major areas of horticulture?

Ornamental horticulture
As you might expect, ornamental horticulture is concerned with plants that are grown for their beauty. This can involve the growing of plants both indoors and outdoors. The color green is obviously a regular feature of this type of horticulture which is why it’s often referred to as the green industry.
Olericulture:
Olericulture is concerned with vegetable crops such as sweet corn and potatoes. It’s not just concerned with the growing of these vegetables. Every aspect of the growing and selling process is covered by the topic. This includes the planting of vegetables, harvesting, storage and selling. There are nine major categories for these vegetable crops:
Pot herbs and greens, which includes vegetables such as spinach
Salad crops, which include lettuce and other vegetables that you would expect to find on a salad
Cole crops, which includes cabbage and cauliflower
Root crops, which includes potatoes and other tubers

Pomology
Pomology covers the same processes as covered by olericulture, except relating to fruit and nuts. The pomology industry is hugely important, as these types of food are vital to the health of the population. At a time when there is greater emphasis on eating less meat and more plants, nuts and fruits supply many of the nutrients that are essential for healthy living.