Tree are normally purchased in three common forms: bare-root, balled and burlapped, and container-grown. All are acceptable, but each has their limitations. Bare-root trees are normally less than 6.5 cm (2.5 inches) in diameter and are normally transplanted in the October to November and in the March to mid-May periods. These plants are sold with the roots tightly packed in a moisture-retaining medium that is wrapped with paper or plastic. Alternatively, they will come with their roots loosely covered by a moist packing medium. If your bare-root tree cannot be planted soon after purchase, you will need to temporarily plant them (heeling them in). Remove the packing materials and cover the roots with soil or organic matter (e.g., wood chips) and water them regularly to prevent drying of the root system. Some trees are moved with a ball of soil protecting their root system. Smaller soil balls should be carried with a hand under the ball. Carrying a balled tree by the stem or branches can result in a seriously damaged root system. With larger trees, the soil balls are often very heavy (100 lbs per cubic foot of root system) and, consequently may require additional handling equipment or engaging the services of a professional tree care company. Mulch and water the trees thoroughly if they cannot be planted soon after purchase. Many tree types are grown in containers. The main advantage of this type is that planting can occur year-round, as the root system is undisturbed. Roots must be pruned immediately before planting. If container grown plants cannot be planted at the time they are purchased, place them in a sheltered location. Water them to keep the soil moist. Container-grown plants can be transplanted anytime when the soil temperature is 10 C (50 F) or higher. This allows time for the plant to be established prior to the onset of winter and to avoid damage from the freezing and thawing of the soil during winter following planting. A word of caution: container grown trees can develop problems with girdling roots. If the tree has tightly-packed roots circling around the inside of the container, it will take longer for the tree to get established and will be more likely to develop a problem.