hydrangea
( hye - DRAIN - jee - uh )
At-A-Glance InformationHydrangea, commonly called Hortensia, is a genus of flowering deciduous shrubs and vines that require partial shade and regular water. Leaves and flower clusters are large, and blooms in summer and fall can be white, pink, red, or blue. These shrubs are renowned for their blossoms, and are true garden classics. Some species' flowers will attract bees and other pollinators, others are sterile and do not provide a food source for these animals. Grow Hydrangeas in borders, in pots, and along walkways and near patios where their blooms can be truly admired.
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Hydrangea Species and Varietals
The genus Hydrangea includes about 75 species and many different cultivars, and is a member of the plant family Hydrangeaceae. The genus name is derived from the Greek word for water vessel, referring to the shape of the seed pods left behind after flowers fade. The best growing zones for Hydrangea depend on the species. For more information, see the descriptions below. To find your zone, click here: Zone Map.
Hydrangea anomala petiolaris (Hydrangea petiolaris) (Climbing Hydrangea) This species takes the form of a vine, and grows best in zones A2, A3, and 2-21. This vine is native to Russia, Korea, and Japan. This vine can climb very high (up to 60 feet tall) but can get shrubby without support structures. Green, heart-shaped leaves and flowering branches hold white blooms that form in clusters 6-10 inches wide. |
Hydrangea arborescens (Smooth Hydrangea)
This shrub grows best in zones A3 and 1-21. Native to the Eastern to Middle United States, it has an upright, dense growth to 10 feet tall and wide. Greyish green leaves and white flowers. This species produces flowers that bees and other pollinators love. Varieties of this species are outlined below.
This shrub grows best in zones A3 and 1-21. Native to the Eastern to Middle United States, it has an upright, dense growth to 10 feet tall and wide. Greyish green leaves and white flowers. This species produces flowers that bees and other pollinators love. Varieties of this species are outlined below.
Hydrangea aspera This shrub grows best in zones 4-9 and 14-24. Native to Eastern Asia, this is a formidable shrub that grows to 10-12 feet tall and wide. Dark green leaves and flat clusters of purple-white-pink flowers. This shrub's form can be improved by cutting back hard for the first three years. |
Hydrangea macrophylla (Hydrangea hortensia, Hydrangea opuloides, Hydrangea otaksa) (Bigleaf Hydrangea, Garden Hydrangea)
This shrub grows in zones 3b-9, 14-24 and H1. Native to Japan. It has a symmetrical, rounded habit to 4-8 feet tall and wide. This species produces flowers that bees and other pollinators love. Varieties of this species are outlined below.
This shrub grows in zones 3b-9, 14-24 and H1. Native to Japan. It has a symmetrical, rounded habit to 4-8 feet tall and wide. This species produces flowers that bees and other pollinators love. Varieties of this species are outlined below.
'Glowing Embers'
Blooms only on old wood. 6 feet tall and 8 feet wide, with deep pink flowers. |
'Madame Emile Mouillere'
Blooms only on old wood, 6 feet tall, 6-8 feet wide. White flowers with blue or pink eyes. Fall foliage turns orange-red. |
'Nigra'
Dark purple to black stems with light green leaves and flowers that can be anywhere from soft pink to blue. Blooms only on old wood. |
Hydrangea paniculata
This shrub grows to 10-20 feet tall and wide. This native to Japan and China grows best in zones A2, A3, and 1-21. Paniculata has dark green leaves. Flowers are in elongated clusters of greenish white to begin, and mature to a pink color. Blooms last for months, and spent spikes can be pruned to give the plant a more neat look. This species produces flowers that bees and other pollinators love. Prune to shape the plant during the dormant season. Varieties are outlined below.
This shrub grows to 10-20 feet tall and wide. This native to Japan and China grows best in zones A2, A3, and 1-21. Paniculata has dark green leaves. Flowers are in elongated clusters of greenish white to begin, and mature to a pink color. Blooms last for months, and spent spikes can be pruned to give the plant a more neat look. This species produces flowers that bees and other pollinators love. Prune to shape the plant during the dormant season. Varieties are outlined below.
Hydrangea quercifolia (Oakleaf Hydrangea)
This shrub grows in zones 2b-23. Native to the south-east United States. This species forms a shrub 6 feet tall and 8 feet wide. Lobes are deeply lobed, resembling oak leaves, and turn bronze or red and autumn. Produces clusters of white flowers that turn pinkish purple as they age. This species produces flowers that bees and other pollinators love. Prune after blooms expire. Sensitive to temperatures below -10 degrees Fahrenheit; the cold can damage flower buds and new growth. In these areas, the foliage of this species is still a beautiful sight in the garden. Varieties are outlined below.
This shrub grows in zones 2b-23. Native to the south-east United States. This species forms a shrub 6 feet tall and 8 feet wide. Lobes are deeply lobed, resembling oak leaves, and turn bronze or red and autumn. Produces clusters of white flowers that turn pinkish purple as they age. This species produces flowers that bees and other pollinators love. Prune after blooms expire. Sensitive to temperatures below -10 degrees Fahrenheit; the cold can damage flower buds and new growth. In these areas, the foliage of this species is still a beautiful sight in the garden. Varieties are outlined below.
Hydrangea serrata
This shrub grows in zones 3b-9 and 14-24, and is native to Korea and Japan. Gets to 4-6 feet tall and wide. Prune after blooms expire. Varieties are outlined below.
This shrub grows in zones 3b-9 and 14-24, and is native to Korea and Japan. Gets to 4-6 feet tall and wide. Prune after blooms expire. Varieties are outlined below.
'Beni Gaku'
Pale blue surrounded by white, red-edged flowers that age to purple. |
'Bluebird'
Deep blue flowers surrounded by pale blue. |
'Fuji Waterfall'
3-4 feet tall and wide, with double white flowers. |
'Woodlander'
Compact variety, grows to 4 feet tall and wide. Leaves mature to a dusky purple. White to pale pink flowers. |
Caring for and pruning Hydrangea shrubs
Before you choose the Hydrangea you'd like to plant in your garden, there are a few things to think about. Hydrangea shrubs fall into two general categories; Group 1 and Group 2. The first group includes Panicle Hydrangeas (Hydrangea paniculata) and Smooth Hydrangeas (Hydrangea arborescens). This group forms their buds in early summertime on new growth, and will flower well each year without a lot of extra work involved. Group 2 includes Big Leaf Hydrangeas (Hydrangea macrophylla), Oakleaf Hydrangeas (Hydrangea quercifolia), Mountain Hydrangeas (Hydrangea serrata), and Climbing Hydrangeas. If you live in a warm area, this group of Hydrangeas may do better in your garden; they set flower buds in fall on old wood and these buds are prone to frost damage (and subsequent drop) if not given adequate protection from the cold.
Plant Hydrangea shrubs in fall in early morning or late afternoon, and in soil that is well-draining. Soil should have a pH of between 6.0 and 6.2 (acidic). Amend soil with plenty of organic material before planting. Applying a layer of mulch at the base of the plant can help to protect the roots and help soil moisture retention. These shrubs need regular water for the first two years after planting, especially during times of drought. Water in the morning at the base of the plant. Hydrangeas need some protection from frost, so either move your plant to a more protected area or indoors (if it is grown in a pot), or you can also cover the plant when temperatures drop too low in wintertime.
The schedule for fertilizing Hydrangea shrubs varies, depending on which type you have. In general, these shrubs like to get fed with a balanced, slow-release fertilizer, for example a 10-10-10 or a 12-4-8. For Bigleaf varieties, feed lightly several times during the months of March, May and June. Oakleaf and Panicle Hydrangeas should be fed twice a year in April and June. Finally, Smooth Hydrangea varieties should be fed one time each year in late winter. Pruning Hydrangeas also depends on which type you are growing. Refer to the chart below for pruning times:
Plant Hydrangea shrubs in fall in early morning or late afternoon, and in soil that is well-draining. Soil should have a pH of between 6.0 and 6.2 (acidic). Amend soil with plenty of organic material before planting. Applying a layer of mulch at the base of the plant can help to protect the roots and help soil moisture retention. These shrubs need regular water for the first two years after planting, especially during times of drought. Water in the morning at the base of the plant. Hydrangeas need some protection from frost, so either move your plant to a more protected area or indoors (if it is grown in a pot), or you can also cover the plant when temperatures drop too low in wintertime.
The schedule for fertilizing Hydrangea shrubs varies, depending on which type you have. In general, these shrubs like to get fed with a balanced, slow-release fertilizer, for example a 10-10-10 or a 12-4-8. For Bigleaf varieties, feed lightly several times during the months of March, May and June. Oakleaf and Panicle Hydrangeas should be fed twice a year in April and June. Finally, Smooth Hydrangea varieties should be fed one time each year in late winter. Pruning Hydrangeas also depends on which type you are growing. Refer to the chart below for pruning times:
Hydrangea Pruning Times
Type
Bigleaf Hydrangea (Hydrangea macrophylla) Oakleaf Hydrangea (Hydrangea quercifolia) Panicle Hydrangea (Hydrangea paniculata) Smooth Hydragea (Hydrangea arborescens) Mountain Hydrangea (Hydrangea serrata) |
Pruning Notes
Prune in summertime after flowering fades Prune in summertime after flowering fades Prune in late winter, before spring new growth appears Prune in late winter, before spring new growth appears Prune in summertime after flowering fades |
Bloom Location
Old growth Old growth New growth New growth Old growth |
Hydrangea shrubs that bloom on the previous season's wood form flower buds in late summertime. These buds hold on through the fall and winter, and open in the next spring season. Avoid pruning these types after the beginning of August; cut away dead or damaged wood in early springtime or fall. In late springtime or fall, cut back one or two of the largest stems to the base of the plant and deadhead as needed to remove spent flower heads. To rejuvenate, cut the entire plant to the base. The plant will lose is flowering capability for a year, but will come back strong in the next. Hydrangea shrubs that bloom on the current season's wood should be pruned in wintertime when the plant is dormant. Prune only remove dead or damaged branches, and deadhead as necessary. These shrubs do not need and do not respond well to much shaping or sizing pruning, so choose a species that is right for your space.
Propagation
Hydrangea can be propagated either by using cuttings or from seed. To ensure that your propagated plant will have the exact same qualities and characteristics as the parent plant, use the cutting method. If you would like to experiment and see what plant you can grow from seed, just keep in mind that it will not necessarily be the same as the parent plant. To propagate your shrub, follow the instructions below:
Propagating Hydrangea by Cutting
Propagating Hydrangea by Seed
Propagating Hydrangea by Cutting
- Gather your materials. You'll need a clean, sanitized, sharp pair of garden shears, rooting hormone, a pencil, and a 3-inch pot filled with well-draining compost or other organic material. If you don't have any potting medium on hand, you can make some. Just mix together equal parts (by volume) moss peat and horticultural-grade sand or grit sand.
- In spring or early summertime, choose the plant that you'd like to propagate. Ensure that this plant has had a good watering the night before, as this will improve the chances your cutting will take root. Cut one or more semi-hardwood non-blooming branches and strip all but the top two leaves off. Shorten the cutting so that it is about 5-6 inches long, and discard the bottom. Make a hole in your planting medium by pushing your pencil into the soil. Dip the end of the stem in rooting hormone, and plant it in your pot. Fill in soil around the cutting to support it, but do not pack it down too much.
- Moisten with water, and ensure that the pot has good drainage. Your pot should be kept in warm, sunny conditions indoors (and not in direct sunlight). Water whenever your soil is dry under the top layer. After about one to two weeks have passed, your cutting should be rooted. When you notice new growth, you'll know you have roots.
- Keep your new plant in an area with bright light (though not direct sunlight) and temperatures between 55 and 70 degrees Fahrenheit. Ensure that the soil stays moist, but not wet, until the next spring, when you can transplant it to its new home. Ensure that the last frost of the year has occurred before doing this, as it can seriously damage your new shrub.
Propagating Hydrangea by Seed
- Keep in mind that the plant you get from seed will not necessarily mimic all of the characteristics of the parent plant. To propagate by seed, you will need a paper bag, a pot or tray filled with well-draining compost or other organic material, a spray bottle and a fork. If you don't have any potting medium on hand, you can make some. Just mix together equal parts (by volume) moss peat and horticultural-grade sand or grit sand. You will also, after a few weeks, need individual 3-inch pots for each seedling that grows.
- Harvest your seeds. The seed pods on Hydrangea shrubs are left behind when flowers fade in late summer or fall (depending on the variety grown).
- Caesalpinia seeds have a hard coating that protects them, but this coating also makes it a little difficult to get them to germinate. We can help the process along by scarifying them with sandpaper (or simply rubbing them against an abrasive surface). Do this with as many seeds as you can; they will probably not all sow, and the ones that do will be of varying characteristics. The more seeds you plant, the more chances you will have to get the resulting shrub you want. Place your seeds in lukewarm water for six hours. Viable seeds will sink to the bottom, and non-viable seeds will float to the top. You can discard any seeds that float.
- Water your prepared seed tray or pot filled with soil, and ensure that good drainage is occurring. Place your seeds in your prepared pot or seed tray about a quarter inch to a half-inch under the soil surface. Cover them with soil and water with your spray bottle. Place your tray of seeds in a warm area that receives bright, indirect light. A greenhouse is the most ideal climate, but a planting tray inside a window will do as well. Germination usually takes 7-14 days from sowing. Once you begin to see seedlings sprout and they are able to be handled, transplant them to their own individual 3-inch pots, filled with the same potting medium as described in Step 1. Loosen the seedlings from the potting medium by digging down with the tines of your fork about an inch and a half, gently working the seedling up until it is out. Then, replant the seedling in its individual pot.
- Keep the seedling's potting medium moist, but not wet, by spraying the soil with your spray bottle. Keep your new plant in an area with bright light (though not direct sunlight) and temperatures between 55 and 70 degrees Fahrenheit. Ensure that the soil stays moist, but not wet, until the next spring (after the danger of frost has passed), when you can transplant it to its new home.
Problems and Pests
Although Hydrangea shrubs are generally pest and disease-free, if they are stressed they can develop some issues, such as:
- Blight
- Leaf Spot
- Crown or Root Rot
- Rust
- Nematodes
- Aphids
- Spider Mites
Gallery
Videos
How to grow Hydrangeas in your garden.
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Propagating Hydrangeas.
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How to prune your Hydrangea shrubs.
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These Hydrangeas produce show-stopping flowers.
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A how-to video on growing Hydrangea shrubs in containers.
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Having some trouble getting your Hydrangea shrub to bloom? Watch this video to discover a solution.
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Resources
The New Sunset Western Garden Book: The Ultimate Gardening Guide (2012) - Pages 367 - 369, Hydrangea
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