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Hydrangeas are one of the most popular flowering shrubs in the landscape today. Prized for their showy blooms and long-lasting flowers, in my opinion, they are a must-have for almost any garden. They come in a variety of forms to small and medium deciduous shrubs, to climbers, and small trees. They're versatile, thriving in partial shade and full sun making them easy to incorporate into almost any landscape. Hydrangeas are one of the few flowering plants that can add a pop of color to your outdoor space for much of the growing season and into autumn.
If I had a dollar for every customer that has asked me, "why is my hydrangea not blooming," I'd be able to purchase a beach house for the cat and serve him a plate full of minnows at teatime. Hydrangeas are among the most misunderstood plant in the garden. Years ago, when I bought my first house, I had a beautiful lush green hydrangea in the front bed. It never bloomed and seemed content being just a big, dumb, green shrub. The first year I accidently dropped an A/C unit on it from the second story window. It squished it to a pulp. I thought for sure I killed it, but it came back with vengeance. In the five years I lived in that house, it never produced anything but big green leaves. I was perplexed. It seemed healthy and determined to live, so why wouldn't it bloom? I started investigating, by reading articles and talking to gardeners. The terms "new wood" and "old wood" were common gardener lingo, thrown around like cheap bird seed. It left me wondering, what on earth were they talking about?
Big-Leaf Hydrangeas
When people think of hydrangeas, many will be referring to the hydrangea macrophylla or big-leaf hydrangea. These mophead hydrangeas are famed for their blue color. A few years ago, I was in Cape Cod for a quick summer getaway. I was in awe seeing these blue beauties everywhere. Even houses that looked abandoned, tangles of them were bursting in blue. It made you believe they are easy to grow, but travel a few hours inland throughout New England, or even into Upstate New York and you'd be hard pressed to find one blooming. Here in the Northeast, blue hydrangeas started to become popular in the late 90s. Garden centers showcased their big blue flowers and listed them as a must for gardens in the north, selling thousands to all of us. What they failed to recognize was that this plant produces its flower buds in late summer then carries them throughout the winter to bloom the following season. This is where the term "old wood" comes from; mature stems that are more than a year old. While the plant is cold hardy in Zone 5 as advertised, it's buds are not. Cold winters and sporadic springtime temperatures swings often kill the buds leaving you with no flowers and just a big, dumb, green shrub. In the coastal areas, it's a tad bit warmer making this location more ideal for flower production. Plant breeders have created and continue to create new hydrangeas that produce a more consistent blue flower in colder climates. The endless summer hydrangea is a bigleaf hydrangea believed to be cold hardy down to zone 4. Flower production will still vary from year to year in the North with some summers still leaving you with no blooms. If your heart is set on having the blue and you live in Zone 5 or colder, plant these hydrangeas in a location that is protected from the wind, near a fence or the foundation of your house. Wrap them in several layers of burlap in late fall and remove it after the danger of frost. Oakleaf Hydrangeas
Oakleaf hydrangeas are one of the few hydrangeas native to the United States. Like the big leaf, they also bloom on "old wood". Their lobed leaves really do look like an oak leaf. Flowers are typically white with some pink varieties. Their lovely fall color and peeling bronze bark can add four-season appeal to your landscape. Unlike the big leaf hydrangea, oak leaf is slightly more adapt in colder climates, but it too can struggle with flower production after a late spring freeze. I like this plant and I've found that it usually blooms, some years more prolific than others.
Smooth Hydrangea
If someone refers to a hydrangea as blooming on new wood, it simply means the flower buds will form on new growth in the spring. These hydrangeas are among the most robust and reliable producers of large flower heads because you don't have to rely on the flower buds overwintering. They can be cut back in the late fall or winter making them quite forgiving of incorrect pruning. Hydrangea arborescens or smooth hydrangea is another hydrangea native to the United States. It's sometimes referred to as a wild hydrangea because it originates from woodlands of moist soil near riverbanks and under the canopies of hardwood forest. Common cultivars include Annabelle and Incrediball. This type of hydrangea produces giant white flowers on new wood making it one of the most reliable hydrangeas for northern climates. It's often seen in mass plantings as a hedge or around foundations. It has a reputation for flopping over especially after heavy rain, but newer varieties have created cultivars with sturdier stems.
Panicle Hydrangea Panicle hydrangeas are my favorite type of hydrangea. They are excellent producers of large white flowers turning to a shade of pink or cranberry in late summer or early fall. They too produce their flowers on new wood and can be a standalone shrub or small tree. Their stems are much sturdier than the smooth hydrangeas. They make elegant cut flowers and can be dried for long lasting home décor. Common varieties include Limelight, Little Lime, Bobo, Fire Light, Strawberry Sundae, and Quick Fire.
How to Prune Hydrangeas
Some varieties of hydrangeas can get BIG, so choose your location wisely. The big leaf and oakleaf hydrangeas are best planted in an area where they are free to grow without interference. Pruning is not recommended for these varieties but if it is required, cut back to the desired height in late fall or winter, knowing you will not get flowers the following year. If light pruning is needed on a branch or two, cut back to a leaf node in late summer.
Smooth hydrangeas can be cut back to the ground in late fall or early winter. New stems will emerge in the spring. Panicle hydrangea shrubs can be cut back to as little as 10 inches from the ground in late fall or winter. Often times these hydrangeas are cut back to control their size and to maintain a compact shrub form. Many people like to leave these hydrangeas up until late winter to add interest in a winter garden and create a habitat for birds.
Hydrangea Care
Hydrangeas are happiest with morning sun and afternoon shade, especially the big leaf varieties. Because of their large leaves, water loss is common in direct sunlight. This will stress the plant leaving many of its flowers to wilt and brow out prematurely. The panicle hydrangea is the best choice for gardens with full sun due to its smaller leaves. Hydrangeas grow quickly and therefore need a lot more water than most landscape plants. Soaker hoses or drip irrigation laid at the base of the plant is the easiest way to keep your hydrangea plants hydrated and it also saves you from constantly dragging out the garden hose. If a hose is your only option, lay it at the base of the plant for a few minutes so enough water can soak the entire root ball. During hot dry spells its recommended to do this at least twice a week. Adding a layer of compost or mulch around the base of the plant will help retain moisture, reducing the plant's water needs.
Fertilizing Hydrangeas and How to Change the Color
Fertilizing hydrangeas is another common misconception. Most require little fertilization and actually too much can limit your flower production. The highly sought after true blue flowers are only found on the big leaf hydrangea. The blue color is dependent upon soil pH. This means this type of hydrangea requires acidic soil to maintain its blue color, or it will bloom in various shades of pink, purple, or light blue. The typical Cape Cod cottage garden is high in acidity due to sandy soil which makes the big leaf flowers turn blue without any fertilization. Further inland, the soil contains clay making it slightly less acidic. A Soil Acidifier must be added around the base of the plant at least twice a season to achieve the blue color if your soil lacks the desired acidity. Early spring and again in early summer are ideal times to add the acidifier.
Soil acidity does not affect bloom color in panicle and smooth hydrangeas. A balanced fertilizer in early spring is sufficient and often times not even needed once the plants become established.
Crafty Ideas
Hydrangeas are excellent cut flowers. A couple plants can give you fresh flowers for your home for much of the season. They can also be dried and incorporated into all kinds of crafty ideas such as wreaths, table arrangements, and ornaments. I love sticking a few in my Christmas tree.