The best time to plant hydrangeas will depend on how you are planting it. Planting times will vary if you are purchasing an already mature, blooming plant from a nursery as well as if you are planting it as a seed or a seedling. The most common practice for hydrangeas, as a result of how long it takes for it to grow and mature, is to purchase it from a nursery when it has already established a fairly decent root system. If you plan on purchasing from a nursery, it is best to buy one that is already in bloom. This will allow you to see how the plant looks when it is covered and flowers. It is also easier to tell if the plant is healthy this way. If purchasing a blooming hydrangea, you can plant it at anytime, though it is best to plant in either the morning or late evening. This will prevent the plant from being damaged by the intense heat of the sun.
If you plant on planting a hydrangea when it is either a seed or a very young plant, it is often best to plant it in the spring, after the last frost has hit. However, it is sometimes difficult to tell when the frost has ended for good. Planting too early or misjudging when the last frost will hit will cause severe damage to the plant and may actually kill it. Avoid planting in the heat of the summer. The plant will have a difficult time getting used to its new environment while it is working in overdrive to keep itself hydrated. The best time to plant is in the early fall, after the heat of summer has passed but before frosts begin. Timing is crucial for the success of your plant.