Totally depends on the size of the pot. a 15 gallon container should accommodate a plant for its entire life. Smaller pots might restrict growth and end up being root bound. Given the option, I would grow all my plants in pots from now on, as it makes water and nutrient management so much easier to control, plus it protects from most garden pests that bother roots. But, if you are concerned about appearance, you can plant in the soil. Or you can do both, by digging a hole large enough to sink a plastic or ceramic pot into the ground, up to its rim, and then planting that way. Try and add a foot or so of gravel under the pot for drainage and offset your post/trellis so it doesn't penetrate your pot and you can sport healthy plants and hidden containers.