Hydrangea serrata [hy-DRAIN-juh serrata] is a deciduous shrub and a member of the family Hydrangeaceae.
The plant is native to Korea and Japan.
The genus name is derived from the Greek word, hydor, which means water combined with the Greek word, aggeion, which means vessel.
The genus name refers to the plant’s capsular, cup-like fruit.
The specific epithet, serrata, refers to the plant’s toothed or serrated leaves.
Common names include:
- Mountain Hydrangea
- Tea of Heaven
This plant grows naturally in moist areas in Japan and Korea. More details on Hydrangeas plant care.
Hydrangea Serrata Care
Size & Growth
Hydrangea serrata is very much like Hydrangea macrophylla, but the overall size of the plant is smaller, and the leaves and flowers are daintier.
Blood-On-the-Snow attains a height and spread of 2′ – 4′ feet.
The plant’s height and spread may be stunted by very cold winters.
Control growth by pruning the plant smaller.
Foliage color is dark green.
Leaves are oval with toothed edges.
The simple, opposing leaves are 2″ – 6″ inches in length.
Flowering & Fragrance
Tea of Heaven bloom time is throughout early summer, mid-summer, and late summer.
Blossoms may be either pink or blue depending on the alkalinity or acidity of the soil.
Alkaline soil produces pink blooms, and acidic soil produces blue blooms.
This is where hydrangea serrata ‘bluebird’ or ‘blue billow’ gets its name.
Unlike many types of hydrangea, the flowers grow in flattened sterile floret clusters or lace caps.
Sterile flowers form around the outer margins of the blossoms, and fertile smaller flowers grow in the center.
Most H. serrata varieties bloom on old wood.
Tuff Stuff is a variety which blooms on both old and new wood.
Light & Temperature
As a woodland plant, part shade is the ideal light setting.
In areas with ample rainfall, the plant will tolerate full sun.
In areas with low rainfall, it must have partial shade during the hottest times of the day.
During dormancy, plants can survive temperatures as low as -13° degrees Fahrenheit (-25° C).
If temperatures plummet in the springtime after new growth has begun, the plant may be killed.
Hydrangea serrata is winter hardy in United States hardiness zone 6 and higher.
It is possible to grow it in USDA zone 5 if you provide it with ample protection through the winter.
You’ll need to mulch around it heavily and provide a burlap wrap.
Watering & Feeding
Mountain Hydrangea requires medium water. Keep a well-draining, evenly moist soil.
When fertilizing hydrangeas the best method is to apply fertilizers in spring or early summer. Use a granular, Hydrangea fertilizer (slow-release) high in phosphorus to help encourage production of blooms.
Soil & Transplanting
Well-draining soil is a must, but this plant can tolerate various types of soil from light to heavy.
This plant grows best in acidic soils (soil pH level 4.5), but a wide range of pH values are acceptable and will produce different colored blossoms.
Neutral to alkaline soil produces pink flowers.
Acidic soil turns hydrangeas blue. Learn more about how to make Hydranegas blue.
Some pH levels will produce lilac flowers.
Although it’s important to prevent having it from standing in water, it’s equally important to prevent the drying of the roots.
A well-draining, loamy soil is best.
Grooming & Maintenance
This deciduous shrub has a compact size and a naturally rounded growth habit so it requires very little grooming and maintenance.
After your Mountain Hydrangea has flowered, you should prune it.
Cut back the flowering stems to the first healthy set of buds.
In early spring, cut away any winter damaged or weak stems.
How To Propagate Mountain Hydrangea
To grow from cuttings, take a 5″ – 6″ inches long cutting from a lower branch.
- Strip off the lower leaves leaving the two lowest leaf nodes in place.
- Cut the largest leaves in half (crosswise) to reduce problems with moisture evaporation.
- Dip the ends of the cuttings in rooting hormone and insert the cuttings into a damp, sterile rooting medium such as vermiculite.
- Water well, allowing the water to drain off.
- You’ll want to keep them medium damp but not soggy.
- Place a plastic bag lightly over the pot.
- It should not be touching the leaves.
- Place the pot in a warm setting with bright indirect sunlight.
- Never expose cuttings to direct sunlight.
You should not need to water again, and you should see roots within two or three weeks.
Hydrangea Pest or Disease Problems
Harsh winters may cause the plant to die back to the ground.
Blooming in the subsequent springtime may be negatively impacted.
Serrated Hydrangea experiences few disease and insect problems.
You may occasionally see aphids (plant lice) on the plants.
Overcrowding and excessive watering can lead to fungal problems such as mildew, leaf spot, bud blight, and bacterial wilt.
Hydrangea serrata is not deer resistant.
Is Hydrangea Toxic Or Poisonous?
Even though some parts of the plant are edible, it’s considered toxic and listed as having poison characteristics.
Some sources assert the flower buds, leaves, and bark are poisonous if ingested and will cause sweating, vomiting, stomach pain, and nausea.
The toxic principle of the plant is a cyanogenic glycoside called Hydrangin.
It’s worth noting this plant is only considered toxic if large amounts are consumed.
The young leaves are used to make a Japanese sweet tea known as amacha.
This tea is used in many Buddhist ceremonies.
The leaves may also be distilled to create a sweetener.
It’s also possible to dry and powder older leaves to use as a spice.
Young shoots and leaves may be added to a stir-fry.
Is Hydrangea Invasive?
There is no indication Hydrangea serrata is considered invasive.
Suggested Uses for Tea of Heaven
Grow groups of hydrangea serrata in sheltered locations such as the border of a hedge or close to your home or an outbuilding.
Individual plants can make nice specimen plants as long as they are provided with good shelter from harsh weather.
Good uses of this plant include naturalizing in a forest or meadow setting or use in the landscape like an old wood shrub.
The long-blooming lacecap flowers attract pollinators.
Given the right setting (a large enough container and space to grow) this compact hydrangea makes a good indoor container plant.