While citrus trees in general prefer warm climates, some varieties of lemon can stand up fairly well to cooler ones as well. No lemon tree type likes cold weather, but if your climate will allow, you may have better luck growing a lemon tree than any other type of citrus. The flavor of different types of lemons varies and may play a role in making your choice as well. The most important factors in choosing a lemon will always be the general health and hardiness of the rootstock.
Examine the lemon tree varieties that will do well in your climate. Your primary considerations should be based on climate. Warm, temperate climates are best for all varieties of lemon. Some species of lemon, such as Meyer, may do satisfactorily well in cooler climates. When possible, it is best to examine the rootstock in person. Online nurseries can sell good products, but it may be more difficult to choose a climate-appropriate plant when you are not dealing with a nursery that is familiar with your area.
Choose a rootstock that looks and feels healthy. Straight, disease and insect-free trunks are desirable. The soil around the root ball should be free of weeds and insects as well. If any grafts have been made, the grafting area should have healed cleanly.
Examine the foliage of the rootstock. The leaves should be healthy and well-nourished, and not at all wilted. Avoid any rootstock with discolored foliage, as this may indicate disease or malnutrition. Lemon trees require a lot of potassium, and will not fare well without it.
Consider how badly you want to deal with thorns. Certain varieties of lemon tree have thorns, while others do not. Lisbon lemon trees have quite a few thorns and can be hazardous to harvest and tend.
Examine the root ball carefully. Any lemon tree you choose should not be potbound, as that is another indication that it was not well tended at the nursery.