Things You'll Need
Hydrangea macrophylla are commonly known as "mopheads" and "lacecaps" for their large, showy blossoms in the summer. Depending on the type of soil in your garden, hydrangea blossoms may appear in shades of blue or pink and occasionally white. Hydrangea macrophylla grows easily in zone 8, but may also do well up to zone 5b, with winter protection. These hydrangeas can grow as large as 4 feet high by 4 feet wide. Plant your Hydrangea macrophylla in the early summer or late fall in an area of your yard or garden where the plant can reach its full size potential without pruning.
Test the soil where you plan to plant your hydrangea. Hydrangeas prefer a slightly acidic soil with pH levels between 4.5 and 6.5. Select an area of your yard or garden that receives morning sun and afternoon shade. Avoid planting hydrangea in close proximity to a large tree as the tree may block too much of the sun. Hydrangeas enjoy shade, but they also crave sun. The farther north you live, the more full sun your hydrangea can withstand. Make sure that the soil drains well.
Dig a hole that's twice as wide as the root ball on your hydrangea plant and only as deep as the container where it is currently growing. Remove the plant from the container and loosen the soil and the roots at the bottom with your hands. Place the hydrangea in the hole and backfill with the soil you removed when you dug the hole. You can mix in organic compost, potting soil or perlite with your garden soil to enrich the soil around the plant.
Water the soil around the hydrangea well after planting. Add a 2-inch layer of bark mulch around the hydrangea plant for moisture retention. Keep the hydrangea moist in hot weather, watering daily as needed.
Fertilize your hydrangea once or twice during the growing season, but never after August. If you live in the south, apply organic fertilizer or 10-10-10 once in May and again in July. For northern growers, one application during the summer in June or July is sufficient. Apply the fertilizer around the drip line of the branches, not close to the trunk. A small hydrangea will only need 1/8 to 1/4 cup, while a large shrub can take between 2 and 3 cups of fertilizer.
Prune your hydrangea in the fall after the blooms are spent or minimally in the early spring when the leaves begin to show. Hydrangea macrophylla blooms on old wood, meaning that the current year's growth will not produce blossoms. Cut back about 20 percent of the plant to maintain its shape. From the end of the branch, count backwards for three healthy nodes. Make your cut just above the third node.
Protect your hydrangea in the winter if temperatures typically reach and maintain single digits or below. Dig them up and overwinter them in containers, or surround the entire plant with warm material.