From our perspective as climbing hydrangeas (Hydrangea anomala subsp. petiolaris), our care begins with the foundation. We are surprisingly adaptable plants, but we have core needs that must be met for us to thrive on your vertical structures. First, we prefer our roots in cool, moist, well-drained, and fertile soil that is rich in organic matter. Think of it as a comfortable, damp bed for our foundation. While we are tolerant of various soil pH levels, a slightly acidic to neutral soil is ideal for optimal nutrient uptake.
Regarding light, we perform best in locations with partial shade to full sun. In hotter climates, we greatly appreciate some afternoon shade to prevent our large leaves from scorching. In cooler climates, we can tolerate more direct sunlight. The most crucial factor is consistent moisture. Our root systems are extensive, and we require regular, deep watering, especially during the first few years of establishment and during periods of drought. A dry root system is a stressed root system, and a stressed plant cannot anchor itself properly or produce the magnificent, lace-cap flowers we are known for.
You may notice that we do not twine like a bean vine or use tendrils like a pea. Our climbing mechanism is unique and requires a specific type of surface. We are self-clinging, meaning we use aerial rootlets along our stems to attach directly to rough, porous textures. These tiny rootlets act like microscopic anchors, gripping onto minute imperfections in brick, stone, or rough-hewn wood. This is a slow and deliberate process for us, not a rapid scramble.
It is vital to understand that we cannot climb smooth, non-porous surfaces like vinyl siding, metal, or painted smooth wood. If you wish to grow us on such a fence, you will need to provide a trellis or a system of wires secured a few inches away from the surface to give our rootlets something to grasp. Please be patient with us during the first two to three years. We are often described as "slow to establish" because we are dedicating our energy to building a strong, extensive root system underground before we commit significant resources to vigorous vertical growth. This patience will be rewarded with a lifetime of reliable, sturdy coverage.
Our natural growth pattern is to send out lateral branches that create a beautiful, layered effect against a wall or fence. We are large, woody vines and can eventually reach heights of 30 to 50 feet and a spread of 5 to 6 feet if left unpruned. This substantial size is something you must plan for; we need a wall or fence that can support our mature weight, which can be considerable over time.
Our structure is part of our charm. We develop a beautiful, exfoliating cinnamon-colored bark on our older stems, which provides winter interest after our leaves have dropped. Our foliage is a deep, glossy green, turning a brilliant yellow in the autumn before falling. The flat-topped, fragrant white flower clusters appear in late spring to early summer, primarily on older branches. This is a critical point for understanding our pruning needs.
Pruning is not something we fear, but it must be done with an understanding of our growth cycle. The primary reason to prune us is to control our size or to remove dead, damaged, or diseased wood. The best time for any significant pruning is immediately after we have finished flowering in the summer. This is because we set our flower buds on the previous year's growth (old wood). If you prune us heavily in the fall or early spring, you will likely be cutting off the flower buds for the coming season.
If we have become too large, you can perform renewal pruning by cutting back some of the oldest stems to the ground in late winter. This encourages new growth from the base. For general shaping, simply trimming back the lateral branches to a bud after flowering is sufficient. Always use clean, sharp tools to make clean cuts and minimize the risk of introducing disease into our stems.
