Light
As with most hydrangea species (Hydrangea arborescens) prefers a partial shade location with dappled sunlight. It can cope with full sun, but shade from the afternoon sun is important in hot southern regions.
Soil
Smooth hydrangeas are adaptable and tolerant of poor soil conditions providing they are moist and well-drained. To thrive, they prefer loamy, rich, acidic soils.
Water
If you live in a region with hot, dry summers or your shrub is growing in the north in full sun, you’ll need to provide your smooth hydrangea with supplemental irrigation during the growing season. It needs moist conditions, and a layer of mulch to help retain moisture.
Temperature and Humidity
Smooth hydrangeas are one of the most cold-hardy hydrangea species and don’t generally need additional winter protection. However, they can die back when winters are particularly cold. The ideal daytime temperatures are around 70 degrees Fahrenheit during the growing season. They prefer humidity over dry areas and should be protected from winds.
Fertilizer
Smooth hydrangeas do well being fed a balanced, all-purpose fertilizer. If you want to increase the number of blooms and their size, select a feed higher in phosphorous, such as one labelled “bloom boost” or with a balance of 10-20-20. Spring feeding is particularly important. Too much fertilizer, however, can burn or yellow the foliage, and too much nitrogen encourages foliage growth rather than blooms. Unlike Big Leaf hydrangeas, the bloom color of the smooth hydrangea cannot be manipulated by raising or lowering soil PH.
Types of Smooth Hydrangea
There are many showy Hydrangea arborescens cultivars to choose from. Some popular options include:
Incrediball hydrangea (Hydrangea arborescens ‘Abetwo’ Incrediball) : Has abundant, spectacular huge flowers and strong, upright stems. Invincibelle Spirit hydrangea (Hydrangea arborescens ‘NCHA1 Invincibelle Spirit’) : What makes this cultivar stand out is that the blooms are pink rather than the standard white color. Hydrangea arborescens (Hayes Starburst) : This cultivar stands out because the blooms are pink rather than the standard white color.
Pruning
Because they bloom on new wood, pruning smooth hydrangeas is easy. Plants can be pruned to the ground every winter or early spring to promote healthy new stem growth and uniform flower production. Alternatively, simply remove any weak or damaged stems.
Propagating Smooth Hydrangea
This fast-growing hydrangea suits propagation from cuttings—root or stem. To propagate softwood cuttings, follow these steps (as long as it’s not a trademarked cultivar):
Common Pests & Plant Diseases
Smooth hydrangeas don’t have problems with any serious pests or diseases, but some common garden pests are attracted to the plants. Keep an eye out for things like aphids, Japanese beetles and spider mites. The common fungal disease powdery mildew can also sometimes be an issue because the plant prefers higher humidity and moisture.
How to Get Smooth Hydrangea to Bloom
With a long bloom period, the clusters of tiny white, sweet-scented flowers bloom prolifically throughout the summer. The flowerheads can grow as large as 12 inches wide and are attractive to pollinators. To encourage healthy, uniform blooms, pruning in the winter is helpful. Too much or too little sun can also impact bloom success, so pick the right location for your smooth hydrangea. And don’t forget to avoid high nitrogen fertilizer, which encourages more foliage than flowers.
