Some give Martha Stewart the biggest share of the credit for creating an American hydrangea obsession. Serious gardeners, new homeowners and casual flower-lovers, all seem to want the huge, silky blue mop-headed flowers that grace the New England landscape.
The craze pushed breeders back to the drawing board to come up with hydrangeas that would bloom as well in Cleveland as they do in Cape Cod. Further, it’s triggered a procession of new varieties, not only of the ones that could be turned pink or blue, but of other species as well. As Martha always says, “that’s a good thing.”
For hydrangeas that can change color, soil with lower pH allows the plant to more easily absorb aluminum if it is present in the soil. There are two types that are capable of changing color. They are:
Bigleaf Hydrangeas (Hydrangea macrophylla).
This species has very large, somewhat rounded leaves, a trait that gives it the common name, bigleaf hydrangea. The flowers are either mophead (round) or lacecap (flat cluster) in shape. While this species blooms on the previous year’s stems, some varieties are remontant, meaning they also bloom more than once per season and even on current year’s stems. Hydrangea macrophylla are hardy in Zones 5-9 and prefer partial sun.
Flowers on the bigleaf hydrangea can vary from the red to the blue and everything between, depending on the soil in which it is grown. Two factors contribute to plant developing blue flowers—the soil’s pH and the presence of aluminum* in the soil. According to American Scientist magazine’s article by Henry D. Schreiber, for the bluing of hydrangea blossoms, one needs both aluminum ions and acidic soil. He recommends using commercially available aluminum sulfate to change a pink hydrangea to blue. An excellent explanation of soil pH and how it affects plant grown is available from Rodale’s Organic Life.
*Note: Aluminum is one of the most abundant elements on the planet: roughly eight percent of the earth’s mass is made up of aluminum, a chemical element that is not required for plant growth.
The first, and best-known reblooming hydrangea is ‘Endless Summer’, a mophead type. The story of how it came to be is interesting and can be found on the Endless Summer website. Since that introduction, others in that category have followed. Personally, I have some in my northern Indiana garden. They include ‘Let’s Dance Starlight’, ‘Let’s Dance Big Easy’.
Mountain Hydrangea (Hydrangea serrata)
Typically more cold-hardy than Hydrangea macrophylla, but with smaller, mostly lacecap flowers, Hydrangea serrata has been catching on in American gardens. This species from Japan and Korea isn’t as showy as the Bigleaf mopheads, but they are subject to color change based on soil pH and aluminum content in the soil. They also produce flower buds on side stems as well as the end of the main stems, providing a continual source of color. Hardy from Zones 6-9 (often hardy in Zone 5), it rarely grows taller than four feet. Varieties that I favor:
Besides the two species that have blue to pink potential, listed below are three others that are worthy of attention for their beauty and no-fuss culture.
Smooth Hydrangea or Annabelle Hydrangea (Hydrangea arborescens)
This American native hydrangea has either lacecap or mophead flowers whose colors cannot be changed. The best new varieties have a more compact stature and stronger stems. Some boast flowers as big as your head, and a few even sport pink flowers.
Hydrangea Arborescens are hardy in Zones 3 -9, prefer full sun to partial shade, and bloom on the current year’s stems. It has fluffy white-flowers and is icon of high summer that goes into a droop after a few rainstorms.
To encourage strong, new growth, and lots of flowers, prune back by one-third its total height in early spring.
Panicle Hydrangea (Hydrangea paniculata)
One of the easiest hydrangeas to grow, as it blooms on current season’s stems, Hydrangea paniculata flowers start out white and change a rosy pink as they slowly age. Panicle hydrangeas bloom on the current season’s stems, and can be cut back by about one third their height in early spring. Hardy from Zone 3-9, they prefer full sun, but also do well in partial shade. Panicle hydrangea grows anywhere from three to 10 feet and has conical-shaped blossoms that typically contain both fertile and infertile flowers.
One of the most important breakthroughs on this species was the introduction of a variety called ‘Limelight’. Almost as soon as word got out about its huge, bright lettuce-green flowers, this 2006 landscape innovation began winning awards for its stunning presence in the garden.
Since then, several new varieties have come out, but ‘Limelight’ is still one of the best. Smaller stature with sizeable flowers and strong stems are what hybridizers are looking for in panicle hydrangeas. Newest varieties include:
Oakleaf Hydrangea (Hydrangea quercifolia)
This American native hydrangea makes a statement from mid-summer into fall. With panicles of creamy sterile and fertile flowers that age to rose, it doesn’t stop there. Hydrangea quercifolia’s large, oak-like leaves turn a gorgeous deep red in fall. Hydrangea quercifolia is probably one of the tallest shrubs you can grow; its dwarf varieties top out around three to four feet. It blooms on previous season’s stems, prefers partial shade, and is hardy from Zones 5-9.
Standard varieties, the tallest of which is ‘Alice’, can grow to eight to 10 feet tall. There is a double-flowered form called ‘Snowflake’, which has been a staple in hydrangea-expert Michael Dirr’s Georgia garden. Flowers on this variety look double because of the way its new sepals (infertile flowers) sprout on top of older ones. ‘Snowflake’ grows up to eight feet tall and 10 feet wide.
One of the best, and most compact varieties is ‘Ruby Slippers’, reaching just three to four feet tall.
Conclusion
Whether you’ve had the success of Martha Stewart or have thrown in the towel on the blue Hydrangea, there are so many varieties to add to your landscape that are cold hardy, heat tolerant, and forgiving of untimely pruning, you’re bound to find one (or several) that you’ll fall in love with.
Terminology:
There are certain flowers and plants that have, for me at least, come to serve as quintessential representations of the seasons. In autumn, I can’t get enough of asters, ornamental kale and the reds, golds, and purples of hardy mums. Winter brings visual interest in the form of evergreens, holly berries, dried seed pods, and eventually hellebores. And spring wouldn’t be the same without the bright, cheerful tulips and daffodils nodding in our front lawns. But nothing evokes the lazy, late afternoons of summer quite like hydrangeas.
At once carefree and elegant, hydrangeas turn this Midwestern girl’s thoughts directly to sunshine, sea spray, and sandy boardwalks. Traditionally a staple of coastal New England gardens, hydrangeas can be grown with great success throughout much of the United States. There are varieties suitable for full sun and full shade and everything in between, and flowers in varying colors, sizes, and shapes.
Plants are a good choice for beds and borders, and of course a white picket fence is an attractive and time-honored backdrop. But consider yourself warned: there’s just something about those oversized blooms that makes me want to scoop them into the wicker basket of my beach cruiser by the armful and pedal off into the sunset.
Perhaps the most instantly recognizable of all the hydrangea species, and the most popular among home gardeners, is Hydrangea macrophylla, commonly known as bigleaf or mophead hydrangea, due to its large, showy, round flowers. Often spotted growing in spectacular borders, along fences, or as foundation plantings adjacent to adorable Cape Cod beach houses, these typically pink or blue flowers have an old-fashioned charm that makes them a classic choice for a formal landscape or a whimsical cottage garden.
H. macrophylla grows and blooms best when planted in fertile, well-drained soil, with a mix of morning sun and some afternoon shade, though in northern climates like the upper Midwest, plants can tolerate more sun throughout the day. These shrubs grow 3-6 feet tall, with a spread of 6-10 feet, making them an excellent choice both in mass plantings and as specimen plants.
Mophead hydrangeas require little to no pruning, aside from the occasional removal of dead blooms and stems, and they should be planted in a location where they can reach their full potential without being transplanted. Fertilizing, with either a chemical fertilizer or organic matter, once in spring or early summer should be all that is required to keep plants thriving.
Bigleaf hydrangeas set their buds in late summer or early fall for the following season, which historically made them a risky bet for gardeners in northern climates where harsh winters and freezing temperatures in late spring threatened blooming. However, new varieties that bloom on both old and new stems have allowed for successful growth as far north as zones 4 and 5.
I discovered Hydrangea aborescens the same way many a frustrated gardener has- I loved the mopheads of H. macrophylla, but just didn’t have enough sun in my yard to sustain them, though try (and try, and try again), I did. Enter H. aborescens, commonly known as smooth hydrangea, my favorite of all the species for its easy care, beauty, and reliability.
Like H. macrophylla, these hydrangeas have huge, ball-shaped flower heads, at times reaching 12 inches in diameter! In fact, these flowers can grow so large they may need to be staked or propped up with a small wire fence to prevent them from drooping. The creamy white flowers are stunning against darker green foliage, and when used in a hedge or mass planting the effect can be striking.
Plants bloom on new growth each year, so they can be pruned back if desired, and cold winter temperatures won’t phase them- H. aborescens is one of the only hydrangeas native to the United States and they are hardy to zone 3! Reaching a height and width of 3-6 feet, this low maintenance plant performs best in part shade, and blooms from early summer right into fall. Smooth hydrangeas are profuse bloomers, and snowball shaped flowers are excellent for cutting.
Another reliable cold weather bloomer is Hydrangea paniculata, hardy to zone 3, and named for its tapered flowers, which form cone-shaped panicles. Unlike most other hydrangeas, H. paniculata actually performs best in full sun, and can reach a height and width of 6-8 feet, with gently arching branches that give the shrub an overall vase shape, making it striking in the background of a perennial border, or ideal as a focal point in the garden.
Blooms are large and pyramidal, first appearing white or pale green in midsummer, but turning a muted, rosy pink closer to fall. Blooming takes place on the current season’s growth, so panicle hydrangeas can be pruned in late winter or early spring, and are the only hydrangeas that can be shaped into tree form, which makes them an excellent and attractive choice for specimen plantings.
Commonly known as oakleaf hydrangeas, due to their leaves’ resemblance to those of an oak tree, Hydrangea quercifolia is, like H. aborescens, native to the United States, though hardy only to zone 5, which means it is, unfortunately, not an ideal choice for much of the Midwest. Similar to H. paniculata, flowers form a spiky panicle and start off white, aging to a deep pink as the season progresses. In fall, the leaves claim center stage as they turn dramatic shades of red, yellow, and orange.
Oakleaf hydrangeas can be grown in much sunnier areas than the mophead varieties, though they will thrive in part shade as well. If pruning is necessary, it should be done immediately after plants finish blooming to avoid removing the buds of next year’s flowers.
Last, but certainly not least, the climbing hydrangea! Hydrangea petiolaris is a robust deciduous climbing plant with masses of white flowers that bloom against a backdrop of heart-shaped leaves in midsummer. Native to Japan and Korea, vines are hardy to zone 4, and will tolerate the entire spectrum of growing conditions from full sun to full shade.
Though it’s a slow starter, once established H. petiolaris can reach heights of up to fifty feet at maturity, with lateral branches extending three feet, making for a dramatic appearance, and providing an attractive privacy screen or covering for a fence, wall, or trellis. Dried flower heads and bark offer visual interest in winter. If pruning is required, it should be done after blooming has ended and before buds for the next summer are set, since plants do bloom on old wood.
When choosing a hydrangea to plant at home, it’s best to consider which of the many different varieties will perform best in your particular growing conditions. Select a spot in your yard with cool, moist, but well-drained soil, and amend with organic matter if necessary.
Once planted, water deeply 2-3 times per week, or use a soaker hose to maintain the proper moisture balance. Hydrangeas are sensitive to over- as well as under-watering, exhibiting symptoms like wilting leaves in each case, so it’s important to establish consistent and healthy watering practices early on. Hydrangeas don’t like to get their feet wet, so avoid planting in sunken areas of the garden, where water will tend to pool around the base of the plant to prevent roots from drowning.
Whether you have an expansive backyard or just a trellis to climb, hydrangeas are an appealing addition to the garden. They provide desirable height and shape, are dazzling when flowering, and the profuse bloomers will reward you with cuttings throughout the summer and into fall. Well, as long as you remember to keep an eye out for brunettes on bicycles.