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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.

Posted on: July 29, 2019 50 Comments
Filed Under: Landscape Design, Woody Plants, Plants, Deborah Silver and Co Inc Tagged With: , , ,

Designing With Hydrangeas

Lots of gardeners in my zone has a love affair going on with hydrangeas. As well they should. They are rangy growing shrubs that deliver a heart stopping show of big luscious blooms from early to late summer, provided they get some regular water, and a decent amount of sun. It is that easy to have a spectacular show of flowers in the landscape in late summer. Even the fall color on the blooms is good.The Annabelles start blooming in June, and are followed up on into August with cultivars big and small –  too numerous to list or review. Every season seems to bring a new collection of hydrangea cultivars to market. It is easy to understand why. They give a lot, and do not ask for much. The oak leaf hydrangeas are equally stunning both in leaf and in bloom, and are incredibly shade tolerant. Our hydrangea season is late this year. Think back to that April we had that was snowy and cold the entire month – you get the picture.  My overgrown Limelight hydrangeas needed a strong pruning this spring. I could not tell now that they had been pruned down to 14″ above grade. They are blooming lavishly. They make me look like an expert gardener. In spite of what I do or do not do, they thrive.

Hydrangeas are easy to grow, but they can be difficult to site in the landscape. They are big growing show offs that don’t naturally play well with neighboring plants. A single Limelight hydrangea can grow easily to 7 feet tall, and 7 feet wide. Even the smaller growing cultivars have giant flowers. They can easily become the elephant in the room-impossible to ignore.  It takes some thought to integrate them into a garden, or a landscape. I am not so much a fan of their woody legs, so I try to place them where that bottom third of the plant is not so much a part of the overall view. I also favor planting blocks of them, meaning I like lots of them as opposed to planting a single plant. They want to be the star of the summer garden, so why not let them show off?  Masses of summer blooming hydrangeas speak to summer in the Michigan garden in a way that no other plant does.

My limelight hydrangeas at home have a long bank of planter boxes placed in front of them. Those boxes are planted with nicotiana alata lime, and nicotiana mutabilis. The boxes hide those long woody hydrangea stems coming out of the ground. The delicate airy mass of nicotiana flowers interact in a contrasting way with those giant hydrangea blooms. The hydrangea flower backdrop makes it easier to see the nicotiana from a distance.

The foliage of the nicotiana repeats the big leaves of the hydrangea. The large leaves are a good foil for the diminutive boxwood foliage. The simple mass of boxwood sets the stage for a late summer.  Nothing can rival the excitement generated in the spring as the landscape roars back to life, but I look forward to this late summer display. On a 90 degree August day, this looks fresh and inviting. The hydrangeas are part of a story.

As a designer, I have a concern about about how spaces come together, and read. Shrubs, perennials,annual plants, and containers have their contribution to make. The design issue is making sure all the various voices work together in some way. The green leaves of the Persian Lime in the center of the pot helps to balance the green of the hydrangea foliage. The big growing hydrangeas need some equally strong minded company.  I did face down my limelight hydrangeas with an outside row of Little Limes. Was that a good idea?  It is too soon to tell, as the Limelights were very hard pruned this spring, so they have fewer and larger flowers this year. This is only the second season for the Little Limes, so they are not yet full sized. They are actually quite different in coloration than Limelight.

This landscape project from last year features a long sweeping curve of upright yews. All that is visible from the street of the Incrediball hydrangeas are the flowers. An annual planting at the base of the yews provides another layer of interest.

Inside the Incrediball hydrangea hedge is a mass of Bobo hydrangea, also faced down with flowers. All those woody stems and leaves are sandwiched in between plants that reveal the best part of these big growing plants, and obscures the least interesting. Hydrangea Bobo is the smallest growing of this series, which means it is the easiest of the three to place. It is perfectly scaled at 3′-5′ tall for smaller gardens. Small spaces can easily be overwhelmed by big growing hydrangeas.

We planted several large masses of these on either side of a pool. The creamy green color of the flowers contrasts dramatically with the color of the water. This hydrangea grows large enough to just obscure the fact that the bed was originally terraced into two levels with large informally placed slabs of stone.

Though the grade does drop considerably and quickly from the pool to the water, the mass of low growing hydrangeas helps to soften the descent. The transition from the pool level to the lake level happens fast.  The hydrangeas provide a reason to slow down, and linger.

The view of these hydrangeas, filtered with tall later blooming perennials and annuals, is a soft and informal look. Hydrangeas are stiff and static growing, and benefit from some airy companionship. Phlox have that same stiff habit of growth. In this arrangement, the phlox looks so much more relaxed, given a static growing plant that is so much larger growing.

There are those places where a single hydrangea can make a statement. This tree hydrangea, one of a pair, spends the winter in my landscape building, in a big plastic pot.  In the spring, it is pruned, both on the top, and the roots, and planted back into this large box. A second pruning a month or six weeks later helps to provide a network of strong branches which will help support the blooms. The box is large enough to permit an under planting of euphorbia, petunias and variegated licorice. Seeing it yesterday for the first time since it was potted up in May was a treat. Part formal and part exuberant, it is everything a well grown hydrangea can be.

Posted on: August 21, 2018 37 Comments
Filed Under: Landscape Design, Woody Plants, Deborah Silver and Co Inc Tagged With: , , ,