Growing and Caring for Hydrangeas

“You gotta love a hydrangea.” A stalwart of the garden, they can be found everywhere. Perhaps it’s their “vintage charm,” evocative of an English country garden. Or perhaps it’s because they are just so dead easy to grow and reward you yearly with flowers that can range from big, bold and colourful, to delicate and demure. Did I mention they are also pretty much pest and disease free? Or that they require very little work to maintain? Seriously easy to love. 

Growing 

This is actually a pretty boring topic, because there isn’t really much to write about… they are easy to grow. Plant them in spot that will make them happy and walk away. Hydrangeas are happy in sun to partial shade, with a moist but well drained soil. I have found that you can cheat a little on the sun exposure, I have seen them happy in some pretty limited shade and also in open sunny areas. The different species and varieties available mean that some are better suited to sun and others to shade. Check the plant label before you buy your plant to make sure you know what you are getting into. But in general terms hydrangeas like to have morning sun and afternoon shade. The one thing that will not work is drought conditions. Hydrangea will wilt easily and if you plant them somewhere too hot and forget to water them, then it’s game over. So, plant some lavender in your dry sunny areas and find a cooler spot for the hydrangea. 

All the Choices 

I think for most people, when you say the name hydrangea the image that springs immediately to mind is of the giant pom-pom mophead style. I remember being fascinated by them in my youth, they appeared to be massive. But, while I love their big, bold, soccer-ball-sized-flowers, there is so much more to choose from these days. Plant breeders have been busy and there are now enough varieties, colours and sizes to suit everyone taste. 

According to most sources there are anywhere from 70-75 different species (that doesn’t include many of the modern cultivars), so I hope you will forgive me if I don’t try to list them all. Instead I’d like to induce you to the five different “classes” of hydrangeas and then give you some of what I believe are the top of their classes. And believe me it’s hard to keep the list small, I want them all. 

Big leaf hydrangeas 

(Hydrangea macrophylla) are the largest group and you guessed it, they have big leaves. This is the most common group and the one most people associate with hydrangea. It can be further broken down into two different types based on the flowers: 

Mopheads

 

These are the grand dame of hydrangeas with their massive ball of flowers. ‘Miss Satori’ is easily my first choice for the best of this group. The first time I saw this hydrangea my jaw dropped, literally. And I’m not the only one to appreciate it, in 2014 it was awarded the Plant of the Year at the famous Chelsea Flower Show. The flowers are large, double and have a stunning variegation of creamy centres and dark rose-pink margins. And the foliage itself gives a look-turning a lovely dark burgundy in the spring and fall. Another great showy group of mopheads are the Cityline Series. These are a group of vibrant and colourful hydrangeas that have a compact growth habit, which makes them perfect for containers or small spaces. Check out ‘Rio’ with purple flowers cantered in blue and the vibrant red and cream of ‘Paris’. 

Lace-cap

These big leaf hydrangeas are distinct for the arrangement of their flower heads, instead of a big ball of flowers they are shaped with more of a flat top, the centre containing small fertile flowers surrounded by a ring of showy sterile florets. My favourite of the group is Lanarth White’ with its demure white flowers and nice tidy growth habit. 

Mountain hydrangea

(Hydrangea serrata), also called the tea of heaven this hydrangea is native to the mountains of Korea and Japan so it’s equipped to handle colder temperatures. The flowers are similar to lace-caps with a centre of fertile flowers surrounded by showy sterile florets. ‘Tuff Stuff’ lives up to its name and there is no sacrifice in the impact of the flowers, which are big lace-cap types with a dramattic saturation of colour. A newer cultivar of Tuff Stuff has recently come across my radar and is making me think that I just might have to make some room on my patio for one more. Tuff Stuff ‘Ah-Ha’ has the most beautiful waterlily-like double flowers that range from a soft blue to light peachy-pink depending on your soil pH (see the insert for more information on this). The other benefit of these shrubs is that they do what is called a repeat bloom so you can expect a show of flowers all summer long. 

Panicle hydrangea 

(Hydrangea paniculatathese hydrangeas also enjoy a certain degree of cold hardiness and can grow quite large (1-5m). They can be pruned and trained to grow into a small tree. They are also some of the best hydrangea for sunny spots, being better adapted for sun exposure. They have cone-shaped flowers which is technically called a panicle hence the name, panicle hydrangeas. ‘Limelight’ is a garden legend that has been loved by many. With large football sized flowers that are an elegant celadon green colour, it’s easy to see why. If you want the same look but have less space then consider the dwarf ‘Little Lime’. Another stand out panicle type is ‘Pinky Winky and if I’m being honest… it is not my favourite name but once you see the flowers you will forget about the name. The large white flowers open in mid-summer and the flowers at the base soon start to turn pink. This creates a lovely two-toned affect, with pink flowers at the base gradating up to creamy white at the panicle tip. 

Smooth hydrangea 

(Hydrangea arborescens) known for the large creamy white flowers, although some of the new cultivars are light pink it is a medium sized shrub that boasts peeling bark and cold hardiness. With the cultivar Incrediball you can forget soccer ball-sized flowers these are basketball sized flowers with strong sturdy stems capable of holding those flowers proudly upright. White flowers in mid-summer that age to a soft green. A definite show-stopper in the garden and a great option for colder interior gardeners. 

Oakleaf hydrangea 

(Hydrangea quercifolia), just like it sounds the leaves of this native North American hydrangea are shaped like an oak tree, and they change colour in the fall just like their namesake. The bark on new stems is soft brown colour with a velvety texture. As the stems mature, they change colour to a cinnamon-brown and are prone to peeling off in an attractive fashion. The flowers are borne in creamy white cones (or panicles) that age to a pinkish hue. These hydrangea are great option if you have site with deeper shade. ‘Snowflake’ is a double flowering cultivar that has won a Royal Horticultural Society Award of Garden Merit, and it’s well deserved. 

Climbing hydrangea

 (Hydrangea anomala subsp. petiolaris) a climbing version of a lace-cap style hydrangea with cream coloured flowers. Technically a liana, which is a woody climbing plant as opposed to a more traditional vine type climber. This is an elegant plant which can be easily left to wind its way around a tree trunk, trellis, retaining wall or anywhere else you might need to cover something. ‘Miranda’ is a particularly lovely cultivar with a green-on-green variegated leaf. 

  

Pruning types 

All of the above types of hydrangeas fall into one of three groups when it comes to pruning. Some form flowers on stems that have grown in the current year (new wood), or on stems from last season that have been through a winter cold period (old wood), or a relatively new development are plants that can bloom on both.

Now, before I talk about the different types it’s important to point out that the worst thing that can happen if you do something wrong with pruning is you might lose a year of flowers. That is the worst case. So don’t be afraid to cut back your hydrangeas if you want to control their growth, they respond very well and can even be cut right back to the ground and recover. 

Hydrangea that bloom on old wood need to pruned right after they bloom and I generally don’t prune after August to allow the plants to slow down growth and produce some branches that can mature and form flowers the next season. The types of hydrangea that need this kind of pruning are: 

  • Big leaf 

  • Lace-cap 

  • Oakleaf  

  • Mountain  

  • Climbing  

Hydrangea that bloom on new wood should be pruned in late winter, before the spring growth. In many cases these plants can be left to their own devices and pruned only to remove deadwood. Shaping is generally not necessary with these types, just plant them mindfully paying attention to their growth needs and mature sizing. Hydrangea that need this pruning are: 

  • Panicle 

  • Smooth 

And the last type are relatively new, they bloom on both new and old wood. These are considered repeat bloomers since they can start blooming early in the spring (like the old wood types) and then keep going through the summer (like the new wood types). Some great examples are the Tuff-Stuff and Endless Summer series. Read your labels and you will be sure to spot the repeat bloomers as it understandably a desirable trait that will be well advertised. 

I recently also found out that in the Victorian era “language of flowers” or flower symbolism, hydrangeas symbolized gratitude for being understood. They also signify frigidity and heartlessness… but I’m just going to gloss over those ones and concentrate on the good stuff. I can understand the connection between hydrangea and gratitude because I am grateful that the hydrangea understands that I need a plant to just perform without requiring too much work from me. So, practice a little gratitude and plant a hydrangea. 

  

Sidebars: 

Can I change the colour of my hydrangea? 

Yes, and no. White flowering hydrangea cannot change colour for the simple reason they are lacking pigment and so can only be white.

A few species and cultivars, such as big leaf types Hydrangea macrophylla and mountain Hydrangea serrata, are able to change colour slightly ranging between blue, red, pink and purple. This happens due to the presence of aluminum ions in the soil. When the soil is acidic (pH below 5.5) then the aluminum ions are able to be taken up by the plant and the flowers will be blue or purple. But in an alkaline soil (pH above 5.5) the aluminum ions are bound-up in the soil and can’t be absorbed by the plant, the result is pink or red flowers. Raising or lowering of the pH isn’t always going to mean a colour change because if you don’t have aluminum ions in the soil then there is nothing for the plant to take up not matter what the pH is. Also, many of the newer cultivars are what I call “colour-fast,” no amount of mucking about with the relative soil acidity is going to affect the colourIts more about intensifying the colour you have (bluer blues and pinker pinks). So if you have a type that will change colour and you want to give it a try you can consider adding sulfur or aluminum sulfate to get bluer flowers and dolomitic lime to increase the intensity of your pinks.

 Written By: Ingrid Hoff

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