Purchase a climbing hydrangea at a garden center or greenhouse. Be sure the hydrangea has bright, shiny vines and leaves. Avoid plants that look wilted or that have dead or yellowing leaves.
Choose a trellis for your hydrangea to climb on. Climbing hydrangea needs a sturdy support, so look for a trellis constructed of wood, wire or tubing. If you choose a wood trellis, cedar, redwood and cypress are durable and long-lasting. Metal trellises made of aluminum, copper tubing or wire are sturdy and won't rust. Keep in mind that a flat surface won't be sturdy enough to support a climbing hydrangea, unless it's provided with supports. If you aren't planting the climbing hydrangea near an existing structure, consider using a ladder-type trellis.
Decide where you want to plant your climbing hydrangea. Climbing hydrangea requires well-drained soil and will grow in either partial or full sunlight. If you plant to locate the trellis next to a wooden building, leave 15 to 18 inches between the trellis and the building because as the hydrangea gets larger, it can cling to the wood and cause damage, including rot. If you're planting the climbing hydrangea next to a masonry or brick wall, the trellis can safely be leaned against the wall.
Prepare the soil in the planting area. Work the soil to a depth of at least 18 inches with a shovel or garden fork. Remove all weeds, along with any rocks and large dirt clods, then add 2 to 3 inches of compost or well-rotted manure to the top of the soil.
Install the trellis before you plant the climbing hydrangea. The installation will depend on the type of trellis, but installation may require metal stakes or fencing spikes to support the trellis securely. If you use wooden posts, be sure they're treated with a preservative so they won't rot. If the trellis needs to be painted, be sure the paint is completely dry before you plant the climbing hydrangea.
Dig a hole for the hydrangea 6 inches deeper than the plant's root system and 2 to 3 times as wide. Slide the hydrangea out of its container, and plant the hydrangea in the hole. Make sure the top of the hydrangea's root system is just barely under the top of the soil.
Fill the hole with water, allow the water to drain, then fill the hole with the reserved soil. Tamp the soil down with a shovel as you go to remove any air bubbles. When the hole is filled with soil, water the hydrangea again. If the soil settles, add more to bring the soil level even with the surrounding ground.
Train the hydrangea by wrapping the vine around the trellis. This should be done every few days. When the vine grows 6 to 12 inches, pinch the tip of the vine with your fingers. This will encourage the vine to branch out. Continue to pinch the tips of each new branch after they reach 6 to 12 inches. The vine will be slower getting to the top of the trellis, but it will be much fuller.
Continue to train the vine as needed. Keep the soil moist for the first season. After that time, the roots should be established, and the climbing hydrangea should need water only during hot, dry periods.