Cultivating Hydrangeas

Hydrangeas of varying types have to be the most widely grown summer flowering shrubs of all. How so? The numbers of cultivars bred from the species serrata, macrophylla, paniculata, arborescens, anomala (climbing hydrangea) and quercifolia (oakleaf hydrangea) surely number in the hundreds. The numbers of those hybrids and cultivars commonly available for sale are staggering. And it seems that every year new cultivars are offered for sale. Should you be interested in hydrangeas for your garden, there are many from which to choose. I am by no means complaining. A warm sunny late July day in my zone featuring a blue sky and the hydrangeas in bloom is one definition of a Michigan summer garden. The spring in Michigan is breathtaking for the sheer number and diversity of plants that break dormancy, come on, and bloom. And of course the June garden features the peonies, roses and delphiniums, and countless other perennials. The July and August garden is ruled by the hydrangeas, much to my delight. I do love these robust growing shrubs that grow and bloom profusely. My hydrangeas make me look like an accomplished gardener, and ask for little in return.       That said, I am fairly selective in what varieties I plant. The short version is that I avoid any hydrangea that blooms on the previous year’s growth. Michigan winters can and will kill the latent flower buds. Pink and blue hydrangeas may do well for you, but they are underwhelming for me. I tend to stick with just a few of the available white blooming cultivars. Hydrangea paniculata, notably Limelight, and its compact relative Bobo, is hardy as can be. These cultivars are overwhelmingly generous with their flowers. They are solidly hardy in my zone. My Limelight hydrangeas in my front yard have been there over 20 years, and endured every one of my pruning experiments. I try to dust them with Hollytone in the spring – but if I forget, they grow and bloom anyway. If I am late with the water, the wilted leaves let you know to get out the hose and use it. Should I cut the blooms, they are gorgeous in a vase. The aftermath of a vase full of hydrangeas is a vase full of dry hydrangeas.

I have a number of clients with Limelight hydrangeas on standard in containers. A number of them choose to overwinter them in their pots, against my advice. I am not a fan of overwintering any plants in pots in my zone. Very few plants can tolerate their roots being above ground during our winter. My worries were unfounded. All of those hydrangeas spending the winter in pots came on without skipping a beat. Our past winter dealt a lot of damage to woody plants. I lost the entire top of a picea mucrunata – shocking, this. Four boxwood burned and died near my front walk. It was a sleeper tough winter. I was shocked at the extent of the winter damage this spring. But the hydrangeas in pots did not skip a beat. One pair has been in pots for 8 years now. Really? That is what I call the willingness to be. I decided to try them myself, both at the shop, and at home. Our grower prunes them after they flower, in July, and again early the following spring.  This routine keeps the heads compact and dense.

Cultivating hydrangeas is not that difficult. Site them with more sun than not-meaning 6 hours a day of good sun. . They do like that sun to bloom well. Hydrangeas can be quite shade tolerant, but those in a lot of shade have weak stems and sparse flowering. Have a lot of shade? Try the oak leaf hydrangea. All of the cultivars of Hydrangea quercifolia are very tolerant of low light. The oak leafs are reputed to do very well in southern US locations. They are easy going about the soil composition, but soil that is enriched with organic matter is optimal.  Being large shrubs with a full complement of large leaves, they need a regular supply of water. Don’t be fooled by their wilting leaves on a very hot day. Those big leaves are thin, and they wilt from heat. If they perk up once the sun goes down, and the weather cools, leave the watering for another time. Hydrangeas of one kind or another in my zone have been blooming or are about to bloom for several weeks. Annabelle hydrangeas typically bloom in June here. A very cold spring set the bloom date back a bit, but all of the rain attending that chill resulted in luxuriant growth. The cultivars known as Bobo (a dwarf relative of Limelight) and Incrediball (a more upright and strong stemmed version of Annabelle). The Little Lime hydrangeas are budding up, and will be in bloom soon. As much as my clients might want pink or blue hydrangeas, I discourage planting hydrangeas in my zone that bloom on old wood. Our winters can be breathtakingly cold and hard. The shrubs will survive. The flowers not so much. The Bobo hydrangeas pictured above bloom profusely. The white florets have a decidedly greenish cast. The color of the creeping jenny on these stone stairs echoes that green.

These Bobos are planted in full sun. Do not try this at home unless you have the patience and dedication to monitor the water closely. The flowers will burn and go brown if the plant lacks for water. Some afternoon shade is a good idea. If you have the room, massing hydrangeas can be an especially dramatic look. Their are no hard and fast rules about the spacing. The mature size of a Bobo is 3′-5′, so spacing them at 4′ apart will result in a billowy and undulating hedge. Spacing them at 36″-42″ inches on center refers to the distance from the center of one plant to the center of the next. This spacing will produce a denser hedge or mass. There are pros and cons to every spacing decision. But it is worthwhile to note that hydrangeas grow very fast.

A hydrangea of decent size in a nursery pot means the plants are most likely root bound. This means they will need to be watered faithfully, maybe daily, until they settle in. That water needs to be applied directly to the root ball. A newly planted hydrangea that goes dry can react with singed leaves and flowers.

Enough sun and water and some moisture retentive soil is all they ask for.

A mass of Bobo hydrangea

Even the north sides of these south facing hydrangeas bloom well.

mass of hydrangea Incrediball

On my driveway, a Limelight hydrangea on standard is getting ready to bloom.

The Hydrangeas

Little Lime hydrangeasSometime between mid July and mid August, the Limelight hydrangeas come in to bloom. It is a moment worth waiting for. The fast growing large leaved plants bloom profusely on the current year’s growth. They are easy to cultivate, asking for not much more that some decent light and some regular water. The spectacularly large flowers are a gorgeous mixture of lime green and white. Limelight hydrangeas are known for their sturdy stems, which keep those flowers aloft in all but the stormiest weather. They do need a lot of room. A single well grown shrub can grow 8′ tall by 8′ wide. Hydrangea “Little Lime”, pictured above, is a hybrid of Limelight that only grows 4-5 feet tall, and as wide. They make themselves right at home in an informal or cottage style garden. But its relaxed habit of growth can look just as interesting in an alternative universe –  a more formal planting.

Little Lime hydrangeasThis mature size is not only friendly to smaller gardens, it looks great in a mass planting. This landscape is situated on a very steep slope, so these Little Limes are responding to the force of gravity. Some gardeners may find their sprawling habit unruly and irritating. Others will find them charming, even beautiful. They certainly endow the late summer garden with their willingness to bloom. All of the pictures in this post but one were taken on days with temperatures above 90 degrees.

hydrangea LimelightMy Limelights are 12 years old, or more.  Some years I prune them down to between 24″ and 30″ inches.  Some years I only remove the old flower heads and 6″ of stem. I always prune them in the spring, when the leaf buds begin to swell. The final result in terms of the flowering and height is fairly uniform, year to year, no matter how I prune. This illustrates the important of choosing shrubs whose mature size will fit the space that is available. I have been watering them twice a week for the past several months, as we have had very little rain.  The group to the far right in this picture get the least water, as they are difficult to reach.  They are shorter than usual, but they have plenty of flowers. How reliable they are to grow and bloom is a very good reason to plant them.

after the rainYesterday morning, after an exceptionally heavy and blustery rain, the water soaked flowers had fallen over in to the path. We’ll see what happens once they dry out. There is no staking hydrangeas at this stage.  If you are bound and determined to keep them upright, very stout and tall tomato cages need to be put in place in the spring. If the flower heads do not spring back up, I will cut some, put them in water, and let them dry indoors.

limelight hydrangeaLimelight hydrangeas can provide an easy going and breezy sense of enclosure. My hydrangeas are planted in a block, not in a single row.  Though the shrubs are very open growing, multiple staggered rows provide a dense green screen which makes my front yard garden quite private.

hedge of limelight hydrangeasGiven enough room, a generous sweep of Limelight hydrangeas can be quite architectural in feeling. Once these hydrangeas are pruned in the spring, they are not pruned again until the following spring.  Few deciduous shrubs can tolerate or perform well having been sheared. Hydrangeas are no exception. Prune to the best of your ability in the spring, and then turn loose of them. Looking for a rule?  The plants will tell you a very detailed story. Very few things bother hydrangeas.  They will bloom in part shade, but not as profusely. The flowers will be smaller, and the leaves will singe on the edges if they get too dry. I mulch them with bark fines in the spring after I prune. I water infrequently, but regularly. Outside of that, I just enjoy them.

limelight hydrangea Limelight is a hybrid of hydrangea paniculata.  Paniculata refers to the fact that the flower heads of these hydrangeas are comprised of hundreds of individual flowers arranged in a cluster around the flower stalk-this flower form is called a panicle. The individual florets will acquire a pink tinge as they age. When the temperatures cool down in the fall, the flowers will age to rose pink. I water the plants more in the early fall than I do in late summer. Truly?  The sure sign of a plant that has gone too dry are flowers that brown before their time. I do everything I can to extend the hydrangea season. I do leave the flower heads on all winter – why not?  Most of them stick tight throughout the winter for me.

August 10,2016 (64)I do not grow hydrangea Little Lime at home, but I have planted plenty of them elsewhere. Their shorter stature means there are flowers at eye level, on top of this retaining wall.  Had I planted the much bigger Limelight in this location, I would be looking in to the stems from the lower level. I recently planted a row of Little Limes in front of an old hedge of Limelights.  This will insure flowers from top to bottom.

August 10,2016 (71)The Little Limes smaller size makes them quite companionable to a host of other perennial and annual plants.

hydrangea BoboHydrangea Bobo is not related to either Limelight or Little Lime, but it is a panicle hydrangea.  Hybridized by Johan Van Huylenbroeck, the same breeder that developed the Pinky Winky hydrangea,  was patented and introduced by Proven Winners. Topping out at 3′ tall by up to 4′ wide, it is beautiful in a mass. Though this group has only been in the ground for 2 inhospitably hot and dry months, they are blooming.  By next year, the chances are good they will completely cover this large sunny area. I can cross this group of Bobo’s off my list of plantings to worry about. They’ll be back.


















Limelight Hydrangea

limelight hedge 2The photograph above has been repinned from my pinterest page, 10 times more than any other image I have ever posted.  I understand the sentiment behind that.  This cultivar of hydrangea paniculata, Limelight,  bred by a Dutch breeder whose name is little known, and marketed solely by the patent holder, Spring Meadow Farms, is is gem of a summer blooming shrub. This ever willing and easy to grow shrub begins blooming at the end of July in my zone, and represents well into the fall.

Limelight-hydrangeas.jpgHydrangea is another word for summer in the garden.  They grow fast, and bloom profusely.   Small plants gain size and stature just a short time after planting.  Given how fast they grow, if you buy Limelights in pots, be prepared to water those root balls frequently after you plant, until they get established.  I water mine via drip irrigation; hydrangeas appreciate regular moisture.  Once they are established, this is about all the care they require.  They deliver so much, and ask for so little.

limelight-hydrangeas.jpgI get emails almost every day about them.  Will the Limelights grow in Atlanta, or Montreal, or upstate New York, or Houston, Arkansas,  or Canada?  Will they thrive in shade?  I have no knowledge of the performance of this shrub outside of my own zone.  Should you have an interest in growing this shrub, contact your local nursery.  See what they say.  In my zone, this hydrangea is happy in full sun with adequate water, and it will bloom, although not as well, in part sun.

limelight-hydrangeas.jpgA Limelight hydrangea is just about the most easy going and tolerant shrub it has ever been my pleasure to plant.  The big coarse leaves provide lots of texture.  They can endure the coldest winter.  They do not require any staking.  Flower heads that are cut will dry and be beautiful in a vase indoors-almost indefinitely. Once they begin to bloom, every garden featuring them gets gorgeous.

hydrangeas.jpgI have planted plenty of Limelight hydrangeas over the course of the past 9 years.  They are easy to grow.  They are happy in no end of environments.  I would want for all of my clients to experience the pleasure they provide in late summer.  How do I maintain them?  I prune in late March, or early April.  If I have a mind to keep them short, I prune them in late March or early April-when the buds swell.

Limelights-in-a-pot.jpgI do feed them once a year with a balanced fertilizer, although I suspect they would be fine without in good compost enriched soil.  They are happy in containers, as long as they are able to spend the winter in the ground.  Tree form/topiary Limelights can be maintained in this fashion for a number of years.

limelight-hydrangeas.jpgI usually prune them in the same manner as a shag haircut.  I prune the top branches short.  I leave the lower branches long.  If you need the Limelights under 5 feet tall at maturity, trim to 30 inches tall in early spring.  Trim again in early June.  the second trimming is crucial to produce a shorter display.  Plan for a late July bloom.  If you like your Limelights really tall, trim off the previous years flower heads.  Leave them tall.  Plan to eventually under plant them with another shrub that will disguise those long bare legs.   Deciduous shrubs ask for a serious yearly dressing down-should you want foliage to the ground. If you need your hydrangeas to be tall, go easy on the pruning phase-and deal with the bare legs. The other option is to plant hydrangea “Little Lime”.  The flowers and habit are the same as Limelight, but it matures at 4 to 5 feet.

limelight-hydrangeas.jpgThe Limelight hydrangea is a garden friend without so many demands.  Prune, or do not prune so much.  They are happy with whatever water you can provide.  If they need water, the leaves will droop in a dramatic way-you can’t miss it.  It is just about the most gardener friendly shrub it has ever been my pleasure to meet.  This has not been the best gardening season for me.  I have plenty of plants not doing so well with the cold and the relentless rain.  But my hydrangeas are breathtaking-as usual.

limelight-hydrangeas.jpgI truly appreciate the work that has been done by the breeder and the distributor to make this shrub available to me.  It is easy to grow, beautiful in leaf, and spectacular in bloom. I planted lots of them in my garden, and today I am really happy I did. The Limelight hydrangeas are illuminating my late summer garden.   Consider planting some Lime lights.  You won’t be sorry.  I promise you will be charmed. What says summer better than the hydrangeas in bloom?


At A Glance: Hydrangeas Blushing

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