How to Plant, Grow and Care For Hydrangea Serrata

Hydrangea serrata is also known as 'Mountain Hydrangea" and slightly less common than more well known hydrangea species. But that doesn't make their blooms any less beautiful! In this article, gardening expert and hydrangea enthusiast Jill Drago walks through everything you need to know about hydrangea serrata, including planting, care, maintenance, and more!

Written by Jill Drago Last updated: October 2, 2023 | 10 min read

Contents

Hydrangeas are one of the most popular flowering shrubs on the market. They are easy to care for, and there are varieties that will grow in most climates. All of this with the beauty of their flowers and growth habit makes it easy to see why gardeners love these blossoming beauties.

It is quite possible that Hydrangea macrophylla is the most popular species of hydrangea, but another species that’s equally beautiful is the mountain hydrangea or Hydrangea serrata. This species used to be a subspecies of Hydrangea macrophylla, but now is in a class of its own. It may not be as popular, but I am hoping to change your mind about that.

Hydrangea serrata is smaller and will only grow to about 2-4 feet tall. If you are looking for a smaller shrub, this may be the perfect plant for your garden. Let’s get to know this plant a little bit better!

Hydrangea Serrata Plant Overview

Close up of single blooming flower head among green foliage. The flower head has small white flowers in the center surrounded by several flowers with rounded blue petals forming a circle. The leaves are wide and oval shaped with serrated edges. The edge of another blue flower peeks out on the right.


Plant Type Deciduous Shrub Season Summer Pests Aphids, Japanese Beetles, Mites Family Hydrangeaceae Genus Hydrangea Maturity Date 3-4 years	Maintenance Medium Species Hydrangea serrata Growth Rate Rapid Soil Type Well-draining, Acidic Native Area Korea and Japan Plant Spacing 3-6 feet	Attracts Pollinators Hardiness Zones USDA 6-9 Plant With Low Growing Perennials, Annuals Planting Depth Depth of Root Ball Watering Requirements Low Height 2-4 feet

What is a Mountain Hydrangea?

Close-up of a blooming flowers against a background of green foliage. The flowers appear as flattened, lace-cap shaped blooms, with scattered showy light blue, almost white, four-petaled flowers forming an outer marginal ring around tiny blue flowers. The leaves are dark green, oval with pointed ends and serrated edges. — *Hydrangea serrata* is a hardy, shade-loving variety that produces lacecap flowers.

Not too long ago, Hydrangea serrata was Hydrangea macrophylla subsp. serrata. Some still consider it to be a subspecies. The main differences between the two are the size and the hardiness.

Hydrangea serrata is native to the mountains of Korea and Japan, making it an excellent woodland plant or even a good option for a shaded rock garden. The mountain hydrangea is hardy in USDA zones 6-9. This species grows best in dappled shade and rich, well-draining soil.

Their flowers are lacecap for the most part, but there are some mophead varieties as well. These flowers will range in color from pink, blue, or white for the most part. There has been some evidence that shows that Hydrangea serrata will react to soil pH just like Hydrangea macrophylla.

Why Plant Mountain Hydrangea?

Close-up of gorgeous plum purple lacey flowers and dark green oval leaves. Blossoms consist of inner small petal-less purple flowers and four-petal showy flowers arranged in a circle. — This variety has thinner stems and more oblong leaves.

Even though Hydrangea serrata started out as a subspecies of Hydrangea macrophylla, it has evolved into something different. You can expect the same growth habit between the two shrubs.

However, this species has more slender stems and smaller yet oblong leaves than bigleaf hydrangeas. The flowers can be lacecap or mophead, but are predominantly lacecap.

These slight differences present us with a more delicate hydrangea that is a bit softer in appearance. It can still be a showstopper and planted as a specimen, but it can also provide softness to a rigid foundation or be planted in your woodland gardens with grace.

Propagating

There are six green cuttings of several types of flowers, three blooms of different types (white panicle with cone-shaped flower cluster, purple serrata with lacecap flower head, and macrophylla with large rounded light green flower cluster), dark green oval leaves with serrated edges, and shears with dark wooden handles on the wooden table. The cuttings have a stem and several lightly cut green leaves. — One of the most common propagation methods is via cuttings.

If you are looking to propagate your Hydrangea serrata at home, you are in luck. This species is easy to propagate and have a high success rate. The easiest way to propagate Hydrangea serrata is by using softwood cuttings. Softwood is nice fresh green growth, and not the woodier, older stems you may see.

Start by taking a cutting that is about 6 inches long that has a few sets of leaves on it. Remove the bottom set of leaves from the cutting to expose nodes, which are growth points. At this point, you can dip the cutting into rooting hormone if you wish, but this is not always necessary so don’t worry if you don’t have any on hand.

Once you have your cutting prepared, stick it right into some sterile planting medium. Keep your cutting in bright but indirect light and keep the soil moist. You can create a greenhouse effect for your cutting by using a bamboo skewer and a zip-top bag over the cutting. Just make sure the bag does not come in contact with the plant or you risk burning the plant tissue.

Keep monitoring your plant until it is rooted, which should happen in about a month. Harden the cutting off by placing it outside for a week before planting it in the ground.

Planting

The gardener transplants a young small shrub into the soil in the garden. Close-up of black gloved hands holding a young seedling out of a black plastic square container before planting in the ground. Another seedling in a black square container stands on the ground. The seedlings have bright green oval leaves with serrated edges. The gardener is dressed in blue jeans, a dark green sweatshirt and black rubber boots and is squatting down. — Take out the plant from the nursery pot and plant it in a hole twice as wide and as deep as the pot.

Mountain hydrangeas are as easy to plant as they are to grow. Find an area in your garden with dappled morning sunlight and well-draining soil. Be sure to check your plant tag for what the full size of your plant will be. This will help to eliminate any unnecessary pruning, and will make for a happy plant.

Before you remove your shrub from its nursery pot, give it a quick watering. While the water is absorbed, you can begin to dig your hole. Try to dig a hole twice as wide and twice as deep as the pot. Sometimes this can be tough, just make sure there is more than enough room for the plant to stretch its roots. Backfill the hole with garden soil and water again.

Don’t forget your hydrangea once it is in the ground. Check on it regularly, as it will need frequent watering while it becomes established in your garden.

How to Grow

Hydrangea serrata has pretty much the same growing requirements as all hydrangeas. You simply need to make sure you meet the unique growing requirements, including sunlight, soil, water, temperature, fertilizer, etc. Let’s take a closer look at each of these imperative factors you’ll have to consider when growing mountain hydrangea.

Light

Your mountain hydrangeas should be planted in partial shade in your garden. Try your best to make sure that direct sunlight occurs in the morning because Hydrangea serrata are not quite as tolerant of high temperatures and overexposure to the sun. If you live in a warmer climate make sure you keep your soil nice and moist to offset any heat.

Water

Just like the other species, mountain hydrangeas love their water. A goal of one inch of water per week is what you should aim for. This can be achieved by precipitation or by hand watering.

Water at the base of the plant to keep them safe from any fungal diseases. If you are using a hose and hand watering, simply aim your hose toward the ground surrounding the plant. When you are using an irrigation system, talk to your irrigation tech and make sure the heads near your hydrangeas are not splashing up on the leaves.

All you need to do is look at the leaves if you are unsure of whether or not watering is needed. If they look droopy and are pointing toward the ground, it is a good idea to make sure they are watered.

Soil

Just like the other hydrangea species, Hydrangea serrata prefers rich, well-draining soil. Well-draining soil will retain a good amount of moisture but it will not become muddy and flood the roots.

Adding some form of organic matter to your soil will help provide the soil with some bonus nutrients, as well as help the soil retain the correct amount of moisture.

This could be in the form of compost or some shredded leaves. Add whichever you choose into your soil during planting time, and again in the fall or spring when you would typically compost your gardens.

Climate and Temperature

Blooming shrub in a sunny garden. The shrub has large dark green rounded leaves with serrated edges. Several purple flowers bloom, each consisting of small blue-violet fluffy flowers surrounded by four-petal showy purple flowers. — This is one of the hardiest species, able to thrive in zones 6-9.

Mountain hydrangeas are hardy in zones 6-9, making this species one of the more hardy of the group.

Even though mountain hydrangeas have smaller leaves than Hydrangea macrophylla, they are still at risk of losing water through their leaves. While choosing a planting site, try to find a spot that is protected from winds.

Fertilizer

Hydrangeas do not often require fertilizer. If you have provided them with a home that has nice fertile soil, they will be able to get what they need from the soil. But even the best of soils can use a little pick-me-up.

If you wish to fertilize your hydrangeas, use a basic fertilizer in the spring. Avoid fertilizing later in the year because it will push growth that may not survive the winter.

If you are looking to promote blooms, select a fertilizer that has a higher phosphorus count, such as a 10-20-10. Phosphorus is needed for big blossoms, and too might nitrogen will cause the plant to focus on leaf production rather than balancing out the flowers and leaf growth.

Color Changing

Close-up of six lacecap flowers blooming on a shrub above lush dark green oval leaves with serrated edges on a sunny day. Purple-blue flowers consist of small green-blue small flowers surrounded by showy four-petaled flowers. — This species can change color depending on the pH level.

Because mountain hydrangeas are very close relatives to bigleaf hydrangeas you may have some success attempting to change the color of your blossoms.

To achieve bluer blooms you want a lower soil pH, try to aim for 5.5 or lower. To do this you will need to use a product specifically labeled for blue hydrangeas or you can use aluminum sulfate which you can find at a garden center. These two products should be applied once in the early spring, and again in the late spring.

On the contrary, if you are looking for pinker flowers you will need to sweeten your soil using garden lime. Garden lime should be applied twice a year, once in the spring and again in the fall. Any pH from 6.5 and up will provide perfect conditions for pink flowers.

Before applying anything to your soil, it is wise to have a soil test done or at least get a pH meter from a garden center so you know you are not adding anything unnecessary to your gardens.

Maintenance

Close-up of a withered flower on a blurred light green background. Dry faded flowers of dark blue in the center surrounded by white four-petaled drooping flowers. The flowers are white, with brown veins. — Deadhead spent blooms to keep your garden looking clean.

Hydrangeas must rank pretty high on the “beautiful and low maintenance” plant list. Hydrangea serrata is no different. These sweet shrubs don’t require much from you aside from water.

You may choose to deadhead if you like to keep your garden looking neater, but this is not a necessary step.

Pruning

Every type of hydrangea comes with its own pruning requirements. Hydrangea serrata blooms on both old wood and new wood, which is important to remember when you are planning your pruning. They typically will not grow taller than 4 feet and do not require much pruning at all.

Because this hydrangea blooms on both old and new wood, you will want to prune it as if it is only blooming on old wood. Hydrangeas that bloom on old wood will produce flower buds shortly after the blooming period ends. If you wait too long to prune, you will shear off next year’s blossoms.

To prune your mountain hydrangeas, you may want to start by deadheading. Then you should look for deadwood. These stems may be hollow and will wiggle easily. Oftentimes you can pull these out by hand. Removing deadwood will increase the airflow throughout your plant.

If you still want to prune them back, just take a quick peek to make sure there aren’t any buds forming on the branches. If there aren’t, you are in the clear to do your trimming. Use clean gardening shears and make nice cuts that angle away from the center of the plant.

Mountain Hydrangea Varieties

There are several popular varieties of Hydrangea serrata that all require the same growing conditions. You can find a type that blooms in blue, purple, or pink. Let’s take a look at some of the stunning varieties you can find.

H. serrata ‘Blue Billow’

Close-up of a flowering shrub. The flowers are in groups of small blue florets in the center and with several larger showy white four-petaled flowers on the outside of each group, forming lacy caps. Flowers consist of rounded petals arranged in two layers with a purple center. The leaves are dark green, oval, serrated at the edges. — ‘Blue Billow’ is a stunning variety that produces light blue lacecap flowers from summer to late frost.

Plant size: 3-4 feet tall, 5-6 feet wide
Plant zones: 5-9

‘Blue Billow’ is an excellent choice if you live in a northern climate and want a blue blooming variety of hydrangea. The light blue lacecap flowers will begin to bloom anytime from early to mid-summer which keeps the buds and flowers safe from any late frosts. ‘Blue Billow’ is a heavy bloomer, covering the entire plant for many weeks.

The foliage on ‘Blue Billow’ is narrow and lush green, turning to burgundy in the fall. Although this mountain hydrangea is cold hardy, it will perform beautifully in warmer climates with even more dependable blooms.

H. serrata ‘Bluebird’

Close-up of a blooming flowers surrounded by dark green, oval, pointed-tipped, serrated-edged leaves. For each lacecap flower, there are small blue flowers growing in the center, surrounded by several larger showy pale blue flowers consisting of four rounded petals. — ‘Bluebird’ has light blue lacecap flowers surrounding deeper blue small flowers in the center.

Plant size: 3-4 feet tall, 3-4 feet wide
Plant zones: 6-9

‘Bluebird’ is another mountain lacecap hydrangea. The flowers that grow on this variety are light blue with deeper blue fertile flowers in the center. These flowers can reach up to 8 inches in diameter.

This shrub will grow in a mounded form and is great in perennial gardens or foundation plantings. The bloom time of ‘Bluebird’ will span the entire summer. The leaves are deep green throughout most of the season and will turn red in the fall.

H. serrata ‘Diadem’

Close-up of a blooming pink flower under the dappled sun in a garden. The flower consists of small fluffy bright pink flowers in the center surrounded by showy pale pink flowers. The flowers consist of four petals slightly whitish in the center. — ‘Diadem’ is an early flowering variety that has muted blue or pale pink flowers.

Plant size: 2-3 feet tall, 2-3 feet wide
Plant Zones: 6-9

If you are longing for a mountain hydrangea that will bloom a bit earlier than the rest, ‘Diadem’ might just be the choice for you. These flowers, although pH sensitive, come in muted tones of blue and pale pink which are very pretty.

This type will grow to about 6 inches in diameter. A little smaller of a variety, ‘Diadem’ would be great in containers or planted together in a mass.

H. serrata ‘Tiny Tuff Stuff’

Close-up of two-toned lacecap flower blooming in the sun. Large light blue, almost white double-blooming flowers consisting of rounded petals arranged in two layers. These showy flowers surround beautiful small deep blue flowers placed in the center. Dark green leaves in the background. — ‘Tiny Tuff Stuff’ is a dwarf hydrangea with incredibly delicate blue flowers.

Plant size: 1-2 feet
Plant zones: 5-9

‘Tiny Tuff Stuff’ is arguably the most popular Hydrangea serrata variety, and for good reason. Everything about this plant is tiny and cute. The leaves are dainty, and the overall size is compact as well. Even though the flowers are small, there is no shortage of them as they cover the entire plant.

‘Tiny Tuff Stuff’ will rebloom all season long with blossoms that are sensitive to your soil’s pH. This hydrangea is extra low maintenance because of its small size, it will require very little if any pruning at all!

Pests

Close-up of a blue lacecap flower and an orange beetle crawling on it against a blurred green background. The beetle has an elongated orange body with thick black stripes. The flower has small blue flowers that are surrounded by showy purple flowers consisting of four petals each. — The most common pests of *Hydrangea serrata* are beetles and aphids.

Hydrangea serrata does not struggle with any pests that are out of the ordinary. You may run into aphids and beetles. While hydrangeas are not the top choice for wildlife, you will likely find them nibbling on the flowers on occasion.

If you would like to try to prevent these insects, you can spray some insecticidal soap or another preventative spray such as a diluted neem oil solution.

You can also manually remove these insects. You can knock Japanese beetles into a bucket of soapy water, and you can spray the aphids off with your hose.

Diseases

Close-up of diseased leaves infected with the fungal disease Colletotrichum. The leaves are oval, dark green with serrated edges. Zonal brown-black spots on leaf surfaces. — Hydrangeas can be prone to fungal diseases due to improperly created conditions.

When it comes to diseases, hydrangeas in general are pretty resilient. They do struggle with fungal diseases, however. This is mainly because of where they are planted. The shade and moist soil can create a perfect environment for fungal spores to spread, especially in the heat of the summer.

The best way to prevent these fungal diseases from getting out of control lies in your hands. Removing any leaf litter, and potentially diseased plant tissue is a necessity. However, planting at the correct spacing will allow for adequate airflow and will help to prevent the muggy environment that favors fungus spores.

Plant Uses

Close-up of a beautiful pink lacecap flower against a blurred green leafy background. The dark pink center of the domed flower are surrounded by large showy pale pink flowers with four rounded petals each. The flowers are small in the center without petals. — Serrata is perfect for tighter areas that require a more compact shrub.

Hydrangea serrata grow anywhere from 2-4 feet, making it a really great hydrangea species for any garden, but especially for smaller gardens where some of the other varieties will be too overbearing. Make sure you select the right hydrangea type for your garden to ge the most out of them!

As with other species, mountain hydrangeas make really nice mass plantings and would make a great short shrub selection for foundation planting. They also make a great addition to a large perennial garden.

Don’t forget the containers! Plant your hydrangea serrata in large pots in your shady areas such as a covered porch or a patio.

Frequently Asked Questions

Unfortunately, Hydrangea serrata are not deer resistant. Flower and leaf buds have been known to be an occasional wintertime treat for deer. The good news is that, throughout the growing season deer are much more interested in other plants, such as hostas.

If you have a high deer population where you live, I would suggest using netting or burlap over them in the winter to prevent the buds from being nibbled on. There are also deer sprays that will deter them from eating your plants.

Hydrangea serrata are not evergreen shrubs. In fact, no hydrangeas are evergreen. Evergreen plants hold on to their leaves over the window, where deciduous plants will drop their leaves after a frost or two.

If you are looking for an evergreen shrub with large leaves try holly, inkberry, or rhododendrons. These shrubs not only are evergreen, but they also require the same living conditions.

Lacecap flowers are a pretty style of hydrangea flower. They are airy, and as the name states, have a lace-like appearance to them. The flowers are made up of two parts: fertile flowers and sterile flowers.

The fertile flowers are in the center of the flower, and look like foam or tightly closed flower buds. They are not showy, but they do add to the beauty of the overall flower.

The sterile flowers surround the fertile flowers, and resemble the flowers of mophead blossoms. They are larger, and may or may not have a different color than the fertile flowers.

Final Thoughts

I personally think Hydrangea serrata is a greatly underused hydrangea species. The lacecap flowers are darling, and I love the more compact size. If you have not tried growing a mountain hydrangea yet, give it a try!