With its enormous, round blooms and lush, green foliage, Hydrangea macrophylla, or bigleaf hydrangea, is one of the most familiar of all the flowering shrubs. Give hydrangea macrophylla some special attention during its first year, and it will reward you with years of low-maintenance beauty. As a general rule of thumb, plant hydrangea macrophylla in morning sun and afternoon shade. However, hydrangeas grown in northern climates will produce brighter colors in full sun, and hydrangeas in hot, dry southern climates will do better in partial shade.
Choose a planting site large enough to accommodate the hydrangea macrophylla at maturity, which for most hydrangeas, will be about 4 feet by 4 feet. Avoid planting sites where rainwater tends to pool for more than four hours. Without proper drainage, hydrangeas are susceptible to root rot.
Cultivate the soil in preparation for planting the hydrangea macrophylla, using a shovel or a rototiller. Remove weeds from the area, and work an organic material such as well-rotted manure or compost into the top 10 to 12 inches of soil. As a general rule of thumb, apply about 50 pounds of organic matter for every 10 square feet of soil.
Dig a hole two to three times as wide as the hydrangea macrophylla's container. The depth of the hole should be no deeper than the height of the container.
Remove the hydrangea macrophylla from its container. If it doesn't come out easily, thump the side of the container with the heel of your hand to loosen the roots, then guide the shrub out of the container.
Loosen the roots carefully with your fingers, and set the hydrangea macrophylla in the hole. The top of the root ball should be 1 to 2 inches above the soil, so adjust the height if necessary. Fill the hole half full with reserved soil.
Allow water to run slowly into the half-filled hole. When the hole is full, wait for the water to drain, then finish filling the hole with soil, tamping the soil with your foot to remove any air pockets. Don't tamp the soil so hard that it's compacted, because the roots will have a difficult time breaking through compacted soil.
Water the hydrangea macrophylla again, then spread 3 to 5 inches of organic mulch around the bush to control weeds, enrich the soil and conserve moisture. Bark chips, pine needles, chopped dry leaves or straw are all good choices.
Fertilize the hydrangea macrophylla six to eight weeks after planting, using an all-purpose granular fertilizer. Use two cups of granular fertilizer for every 100 square feet of soil. Once the hydrangea is established, water it in spring, early spring, late spring and mid-summer. Be sure to water immediately after fertilizing.
Water the hydrangea macrophylla bush when the top two to three inches of soil are dry to the touch. After the first year, the root system will be established and the plant will only need to be watered during hot, dry periods.