Mountain Hydrangea Hydrangea serrata 'Beni-gaku' (L)

Water

For the Mountain Hydrangea, it should be watered deeply to ensure the roots are sufficiently moist, which typically means using several gallons of water per session, depending on the size of the plant and the soil moisture level. During active growth in spring and summer, watering may be necessary once or twice a week, with reduced frequency once temperatures cool, usually to around once every two weeks. It's important not to overwater, as standing water can lead to root rot – the soil should be moist but not waterlogged. During drought or periods of extreme heat, additional watering may be necessary to prevent stress. Always check the top couple of inches of soil for dryness to gauge if additional water is needed.

Light

The Mountain Hydrangea thrives in partial to full shade conditions, avoiding the harsh afternoon sun which can scorch its leaves. A spot that receives filtered light through tree canopies or dappled sunlight works well. Morning sun with afternoon shade is ideal for vibrant bloom color and healthy growth. If grown indoors, a north-facing window can provide the right amount of light for this plant.

Temperature

Mountain Hydrangeas prefer a temperature range between 60 to 75 degrees Fahrenheit and can tolerate minimum winter temperatures down to 20 degrees Fahrenheit. They can struggle with heat stress when temperatures soar above 80 degrees Fahrenheit, so providing some shade during the hottest part of the day can help maintain an appropriate temperature range. Ideally, they should be grown in environments that closely match their native habitat temperature conditions.

Pruning

Prune the Mountain Hydrangea after it blooms in the late summer to improve its shape, remove any dead or weak stems, and encourage next year's blooms. This plant flowers on old wood, so careful pruning is essential to not remove new buds. The best time for pruning is immediately after flowering, which minimizes the risk of cutting away buds for the next season. A light pruning annually is often enough to maintain health and vigor, with more substantial pruning done every few years to rejuvenate older plants.

Cleaning

As needed

Soil

Mountain Hydrangea requires moist, well-draining soil with high organic content. The ideal soil pH for vibrant coloration is slightly acidic, around 5.5 to 6.5. Amend garden soil with compost and peat moss to improve texture and fertility for optimal growth.

Repotting

Mountain Hydrangea should be repotted every 2 to 3 years or when it becomes root-bound. Preferably, repot in the spring before the growing season begins, allowing the plant to settle into its new container.

Humidity & Misting

Mountain Hydrangea thrives in moderate to high humidity levels, ideally between 50% and 70%. In dry indoor environments, use a humidifier or pebble tray to maintain adequate moisture around the plant.

Suitable locations

• Indoor

  Place Mountain Hydrangea in bright, indirect light indoors.

• Outdoor

  Plant Mountain Hydrangea in part shade with moist soil.

• Hardiness zone

  6-9 USDA

Life cycle

Hydrangea 'Beni-gaku' begins its life as a seed, which, when sown in well-drained soil with sufficient moisture, will germinate in spring under the right temperature conditions. After germination, the seedling emerges and develops into a young plant with characteristic leaves, requiring partial shade and regular watering to establish a healthy root system. As the plant matures, it develops woody stems and enters a vegetative state where foliage growth predominates, and it can be propagated by cuttings. During the flowering stage, typically in early summer, it produces lacecap flowers that display a changing palette of colors from pink to red, requiring more water and occasional feeding with acid fertilizers to maintain bloom vibrancy. In the autumn, the plant's growth slows down, and it prepares for dormancy, during which time it may lose some or all of its leaves depending on the climate. With the return of spring, the hydrangea exits dormancy, resumes active growth, and the cycle repeats with new foliage and blooms, although it may require pruning to maintain shape and encourage flowering.

Propogation

• Propogation time

  Late spring to early summer

• Hydrangea serrata 'Beni-gaku', commonly known as the mountain hydrangea, is typically propagated through softwood cuttings. This method is best carried out in late spring to early summer. A gardener would select a healthy, non-flowering shoot and cut a 4 to 6-inch segment, ensuring at least three sets of leaves are present. The lower leaves are removed, and the cut end is dipped in rooting hormone to facilitate root growth. The cutting is then planted in a moist, well-draining media like a mix of peat and perlite and kept under high humidity and indirect sunlight. Roots usually develop within 4 to 8 weeks, at which point the new plant can gradually be acclimatized to less humid conditions before being transplanted outdoors.