Some people have little space for a full-size Christmas tree. Others prefer a living tree that can be planted after the holidays.
If you prefer a living, compact tree, consider the alternatives. If you buy a small, potted tree such as a blue spruce or dwarf Alberta spruce, dig a hole for it immediately. Store the soil in a garage or place where it won't freeze. Only keep the tree inside for a few days. Warm temperatures inside will disrupt and confuse it. Spray it with an anti-dessicant product such as Wilt-Stop. After Christmas, plant and water it immediately.
Very small potted trees of cypress are available. Some are dark green; the lemon cypress is bright apple green with a delightful citrus fragrance. Since these aren't reliably hardy, grow them as a houseplant in a sunny window; the pot can go outside in summer. Holly can also be grown in this way.
Clipped versions of rosemary, boxwood or lavender that look like Christmas trees are charming. They also need lots of sun in a south or west-facing window and can also be displayed outside in summer. They are best re-potted as soon as you get them. In my experience, most have used up all the soil in their plastic pots and dry out alarmingly fast. Select a new decorative pot several sizes larger than the original plastic one. After re-potting, keep the soil moderately moist.
As the winter solstice approaches, consider creating an arrangement of branches and seed pods from your garden. I like to recognize the beauty of these freeze-dried materials. In doing so, we recall the bounty and beauty of a year that has passed and anticipate the promise of what's to come.