When it comes to beautiful flowers the genus Hydrangea is unrivaled in the shrub world.  This diverse group of plants contains roughly 23 different species native to North and South America, and Eastern Asia. The group offers hundreds of cultivars that are well suited for the landscape and deserve greater consideration.

    It seems that I am not alone in my appreciation for Hydrangea, for this group of plants has found new popularity and its demand is skyrocketing.  And with its increased popularity there has been increased demand for information about Hydrangea. Which species are hardy?  When should I prune them?  Which cultivars are good for drying? Which cultivars are dwarf? How do I get blue flowers and so on.  It has been our business philosophy that providing information is a basic business function. 

There are seven species that are well adapted to our climate and can make a great addition to our landscapes.  Most thrive in rich porous, somewhat moist soils.  Most prefer full sun, however, many  will also grow and bloom in partial shade.  The hallmark of Hydrangea is its large flower heads and its long bloom time. These attributes contribute to its appreciation by American gardeners.

Hydrangea anomala is the Climbing Hydrangea.  We most often see the subspecies petiolaris because it is  hardier (zone 5) than the typical species.  This plant is considered by many to be the Cadillac of all vines. It is a strong grower but not so aggressive that it will tare down a house or fence like many vines.  It is in fact poorly suited for a fence because it does not twine but climbs by aerial roolets.  It is at its best when grown on the trunk of a tall oak tree or covering the face of a brick wall.  It blooms from late June to early July.   Its lightly fragrant, creamy white blooms are 6 to 10 inches across and composed of a lacy center of fertile flowers ringed with a bracelet of larger sterile florets.  The effect is breathtaking and any self- respecting designer should include this plant in his or her arsenal of plants. This jewel is also noted for its attractive thick glossy leaves and its rich brown exfoliating bark.

There are several new cultivars of climbing hydrangea that are worth looking for. 'Skyland's Giant' (image above) is a new variety selected for especially large flowers. 'Fire Fly' is a new variegated selection of climbing hydrangea that is simply spectacular in in the spring when the plant flushes. It has the same great flowers as the species. As the season progressed the variegation becomes less pronounced.

Hydrangea arborescens has the common name of Smooth Hydrangea.  Few people know or have seen this conspicuously flowering species, but we all know its cultivars. Everyone knows the large, snowball-like blooms of Snow on the Mountain the common name for the cultivar ‘Grandiflora’.  Unlike the species, this plant does not have the flat flower head composed of mostly fertile flowers.  It has a big ball of sterile flowers that bow to the ground after a heavy rain. The cultivar most commonly grown today is ‘Annabelle’.  This is because it has the extremely large, tight,  symmetrical blooms, reaching up to  14 inches across. It is widely used in the north because it is hardy to zone 4, and because it blooms on new wood.  The wood will often freeze back in the winter but will still reliably bloom from buds produced in the spring  It can be pruned either in the fall or spring, or in mid to late summer after it is finished blooming.  The one negative attribute of ‘Annabelle’ is that its blooms are so big and heavy the plant will often collapse under its own weight.  Staking is often necessary to keep this plant together. White Dome is a new lace-cap variety that has large lacy dome shaped blooms. It has attractive large dark green leaves and strong flower stems that never flop. This plant is particularly attractive in the winter when the snow settles a top the dried flower heads.

Hydrangea heteromalla is nearly impossible to find in the nursery trade but with the new found interest in hydrangea we may begin to see more of this hardy species.  It is a medium to large shrub that reaches 6 feet in height. Its white flowers  are of the lacecap type, having a loose sterile ring of flowers encircling a fertile grouping.  The noted ornamental attribute of this plant is its variation in flower color as it ages. The 5-7 inch white blooms appear in early July and gradually take on a brickish-pink tone, then a brownish-orange color. Several cultivars are in existence, although I have only seen the straight species. Don’t be surprised to see this plant and its cultivars hit the nursery market in the next few years.

Hydrangea macrophylla, the Big Leaf Hydrangea is extremely popular today because of it is the most colorful of all the species.  Like Hydrangea arborescens, this plant too can be categorized into two main groupings: Mopheads (snowballs) and Lacecaps.  The Mopheads are large round clusters of sterile flowers and the lacecaps are flat heads composed of both fertile and sterile flowers.  The Mopheads are the most popular because we tend to love the gaudy.  The lacecaps are gaining in popularity and are considered by many, including myself, to be even more beautiful because of their delicate looking nature.

  Hydrangea macrophylla is unique for several reasons.  It sets it flower buds in the fall and overwinters them.  A hard winter can kill the buds and eliminate flowering. An early  fall or late spring freeze may also result in a loss of flowers.  Although completely root hardy in Zone 5, the buds should be protected with a light mulch in the North to improve the bloom reliability.  Feedback from growers around the country have provided us with valuable information on bloom reliability.  The most exciting news is that the cultivars Pink Shira, 'Sadie Ray', 'Endless Summer', and 'Forever and Ever' have the ability to bloom on old and new wood alike. If the buds are winter killed the plant will form new buds in the spring and still bloom. These are great selections for the Midwest where it is hard to get Hydrangea to bloom.

 In you live in milder sections of the country consider the new dwarf cultivars sold under the CITYLINE series. These compact plants form a neat compact plant that is covered with blooms.

Another interesting  attribute of this plant is that its flower color may change depending on soil p.H..  It is not the p.H. itself that changes the color, but it is the availability of Aluminum ions that directs the color. Aluminum has greater availability in acid soils thus the blooms turn blue in acid soils.  If the soil is either basic or high in phosphorous, the aluminum is tied up and flowers tend to be pink.  The degree of color change is dependent upon the amount of aluminum ions available and the cultivar itself.  It should be noted that if you are growing in a soil-less mix you may not have much aluminum availability even at low p.H. levels.  Aluminum sulfate treatments would then become necessary to get blue flowers.  Commercial nurseries often tie up the aluminum with high levels of phosphorous.  Pull out your old soil science book and see for yourself.

Many new and rediscovered cultivars of Hydrangea macrophylla are hitting the market.  It’s real exciting to see so many varieties, but only time will tell which are the best for your area.  New breeding efforts are underway to bring us hardier cultivars and more varieties that will bloom on new wood.  Until then, remember to mulch in the winter and to site these plants in a microclimate for best results.

Hydrangea paniculata (Panicle Hydrangea) is our hardiest species and perhaps the best choice for the Midwest.  How can one help but say “oooh!” when we see this plant change daily from its pure white blooms to hues of warm pink. It is unfortunate that many nurseries sell only the tree form of the cultivar ‘Grandiflora’ which we call Pee Gee or P.G. for short.  This plant is noted for its abundance of sterile blooms on its thick conical flower head.  What is unfortunate is that so few growers, retailers and designers have yet discovered the many excellent cultivars now available. Also, it need not be a tree form to look good.  In fact, the plant shows off its flowers better if grown as a shrub.  I particularly like the cultivar Pinky Winky which has very large but delicate, lacy flowers.  Its combination of fertile and sterile flowers gives it a soft intricate look. It is also one of the earliest cultivars to bloom and its flower heads continue to grower as the season progresses. This continued growth results on interesting bi-colored because the older flowers turn dark pink while the new flowers emerge white.   Quick Fire is a very early blooming selection which blooms in late June - early July. It is not as open as Kyushu, but not as dense as Pee Gee.  When used together with other varieties  the bloom period can be extended over three months. Other new cultivars include ‘Little lamb’ which has tighly packed sterile blooms in petit flower heads. The plant is only 3-4 feet tall so it makes a great shrub for around the home.  In the autumn the blooms turn pink  to create a breathtaking floral display.  Perhaps the most exciting news for Hydrangea paniculata comes in two new and markedly distinct new cultivars. Limelight is a fantastic new selection from the Netherlands with exquisite cool green  flowers. The blooms are large and held up on strong stems making a handsome display. The color, may seem odd, but once you seen the flowers you'll be convinced this a great plant that blends wonderfully into any garden or landscape.   In the autumn the bright green flowers transform to shades of pink, burgundy and green all at the same time.

 Hydrangea paniculata The Swan is a new plant from Belgium. It's unlike any other hydrangea, with massive sepals the size of your hand. This is a great selection for cut flower or dried flower arrangements, or for the garden. Take note that The Swan is an ugly duckling as a young plant and takes a few years in the garden to mature into a swan.

Oak Leaf Hydrangea, Hydrangea quercifolia, is a great landscape plant. As its name indicates it has an oak-shaped leaf.  It is noted for its unrivaled  burgundy red fall color.  It blooms in late June - early July and is persistent into winter.  The flower heads are cone-shaped, open white and fade to a pleasing pink and then rich brown. The plant is 6 to 10 feet tall, course in texture, and very useful in the landscape. It sets it buds in the fall and exhibits excellent bud hardiness.  It should thrive in zone 5 even though it is native to the Southeast.  Due to its variability when grown from seed, I recommend the use of its fine cultivars. ‘Snow  Queen’ has consistently good fall color and very large florets arranged in large, erect, dense heads.  ‘Snowflake’ is a doubled flowered form that combines pink and white florets on the same flower.  The extremely large flower heads are so heavy they weep downward making it easy to recognize. Some criticize this attribute, but I like it very much. To each his own!  The cultivar ‘Harmony’ has a very dense, rounded pear shaped flower head with very few visible fertile flowers.  The cultivar ‘Alice’ is also very popular.  It is a selection made by Mike Dirr for its exceptionally fine fall coloration.

Hydrangea serrata is considered by some to be a Hydrangea macrophylla variety and not a distinct species.  Yes the plants are quite similar in many respects, but I personally view these plants as distinct, and hence treat them here as a separate species.  Unlike H. macrophylla, which is native to the coastal climate of Japan, Hydrangea serrata is native to the mountainous regions of Japan and Korea.  Coming from higher elevations serrata tends to be a hardier plant.  The leaves, as the name suggests, are more serrate “having a saw-like leaf margin”  They tend to be smaller, finer stemmed plants, with smaller more linear leaves and nearly all the cultivars being lacecaps.   ‘Bluebird’ is perhaps the best known of the serrata cultivars.  It has clear blue flowers with lighter blue sterile florets with each sepal evenly space, never touching each other. The leaves take on a coppery-red coloration in the fall which is quite pleasing.  ‘Diadem’ is a dwarf plant reaching only 2 feet. It is free blooming and makes a beautiful display. It is perhaps the earliest blooming cultivar, with the flowers appearing in mid-June.  The bloom is dome shaped, 4-5 inches across, with a soft pink or blue depending on p.H.. The cultivar ‘Beni-gaku’ is a long cultivated Japanese cultivar, often depicted in Japanese art. This very graceful plant reaches three to four feet at maturity.  Its flowers, a delicate pure white lacecap, become tinged with red as they age.  An interesting plant that is considered a cross between macrophylla and serrata is ‘Preziosa’.  Its mophead blooms emerge a pure white and gradually change to  a translucent burgundy red by the end of the season. The leaves undergo a similar coloration change as well. If planted in acid soil the blooms will color an extraordinary blend of pale blue, mauve, violet and pale green.  I have also received a lot of good feedback as to the hardiness and bloom reliability.  This is a remarkable plant by any standards!

As you can see the genus Hydrangea is an amazing group of plants.  Is it any wonder that they are so popular?  It is a fun group of plants to learn as well.  There are numerous cultivars in each species that I did not mention that are excellent plants and deserve greater use.  This article is my attempt to give you an overview of the usable species in the genus. A small taste to make you hungry and want to learn more about this outstanding group of plants.  There are several excellent books on Hydrangea that can guide you on your Hydrangea journey.  HYDRANGEA species & Cultivars  by Corinne Mallet is a two volume set that is invaluable to the Hydrangea fanatic. It has excellent descriptions and color plates of hundreds of varieties.  The book HYDRANGEAS by Haworth-Booth is also an excellent resource.  Still the best way to learn your Hydrangeas is to start growing them and see for yourself the beauty and excitement these plants create.  And for those of you who felt this article gave your more information that you ever wanted to know about Hydrangea. The name Hydrangea is Greek meaning “water vessel”. It is derived from the shape of its seed capsule.  My Hydrangea overflowith!

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