by / Monday, 11 June 2018 / Published in Blog


Hydrangeas 101

By Dave Van Raay

Hydrangeas are a summer stunner and one of Canada’s favourite shrubs. Not only do they gain popularity for their significant and vibrant flowers, but the secrets surrounding their chameleon-like colour changes have more gardeners interested each year. To help you make the most of this popular shrub and to get started growing your own impressive globes of colourful blooms in your yard, here’s our advice.

Getting to know Hydrangea

Most species of this blooming beauty call East Asia home, where they can be found covering entire volcanic hillsides in intense blue hues. The varieties that we see in garden centres in Canada range from incredibly tough and hardy, to those that need a little more pampering. With our milder climate, we get a full sampling of the best that hydrangeas have to offer, without stressing too much about our plants surviving the winter.

Basic Care

The everyday basics to take care of your hydrangea are startlingly simple – it’s the pruning that can stump gardeners without some basic knowledge.

Location – While they will grow fine with full sun or partial shade, the perfect spot for your hydrangea is somewhere with a little protection from the afternoon sun. Humidity helps to cut the intensity of the sun rays, but a dappling of shade will help make sure your hydrangea doesn’t fold under the heat and UV. Conveniently, locations with a bit of protection from the sun also offer great shelter from strong winds.

Soil – The key is to keep your soil moist, but not wet. This becomes especially important during heat waves, but your hydrangea will appreciate consistent moisture all season. A few inches of organic mulch is a great way to lock moisture in.

Watering – As we said, your hydrangea will be happiest in soil that is consistently moist. When you water your shrub, water it deeply. Keep in mind that heat waves will leave your shrub more parched than usual, so you’ll need to adjust your watering accordingly. When you water, try to avoid splashing muddy water onto the foliage – mulch can help prevent this, too. Keeping your plant’s leaves clean is especially crucial in cool weather when leaf fungus can set in. This fungus is generally harmless but can ruin the aesthetic of your plant.

Planting – You’ll have the best results planting your hydrangea in cool weather. If you have to plant while temperatures are high, keep their roots moist and provide a 3 in 1 soil compost mix for them to have a good start.


Every year tons of eager gardeners wait in anticipation for their Hydrangeas’ gorgeous bouquets of flowers, only to get an underwhelming season of only leaves. This disappointment usually has pruning to blame, which is easy to fix with a little know-how. Hydrangeas can be broken down into two categories with different blooming and pruning habits.

Old Wood Bloomers

The popular, larger lush-leafed “Macrophylla” varieties – such as Endless Summer, All Summer Beauty, the City Line Series and others – all bloom from old wood. This means that they set their buds in the late summer right after they finish blooming. This way they are prepared all winter to dazzle when the temperatures climb again. Pruning anytime after they set these buds will removed next years bloom potential, and you’ll be left with a pretty, but only  leafy hydrangea next year. To avoid missing out on their flowers, only trim as far back as the winter “dieback,” and remember that trimming less is better. 
This far into the season we’re safely past the new growth phase. You can quickly tidy up by removing any stems that aren’t producing leaves. As the blooming season continues, feel free to deadhead spent flowers to get the best show from these impressive bloomers. 

New Wood Bloomers

Other hydrangea types include those that bloom on new growth. These include “Paniculata” varieties, like Limelight, PG and Little Lamb, and “Arborescens” varieties, like Annabelle, Invincibelle, and Incrediball. These bloomers you can be far more liberal with pruning in late fall or early spring. You can trim them back in either season without being afraid of affecting their summer blooms, which is useful to keep their rapid growth in line.

At this point in the season, it could be a little late to trim them back too aggressively, but you will still be able to safely prune the branches of most varieties by 25-50%, if you feel that it’s needed. Pruning later in the season won’t risk your summer blooms, though it will likely delay them to later in the season.

Colour Changing Hydrangeas

We’ve come to expect the classic colours of vibrant pink and blue from our hydrangeas. One of the most enticing things about these shrubs is the ability to change what colour they bloom! It’s one of the most common questions surrounding these popular plants, and the answer comes down to the magic of chemistry. 
The secret to influencing the colour of your plant’s blooms comes down to pH. Soil that is more acidic will shift the flowers to turn blue, looking just as they do in the volcanic soils of their natural habitat. On the other hand, the same hydrangeas growing in more alkaline soil will bloom pink. 
If you’re excited about experimenting with your plants, you can easily influence your hydrangea to bloom blue by adding aluminium sulphate to the soil to lower the pH. Adversely, if you prefer a pink bloom and the soil you have planted them in has a higher pH level, turning them to a purple or blue hue, adding Dolomitic Lime will neutralize the soil, bringing back your vibrant pink blooms. It is recommended to apply these pH enhancers or stabilizers every two weeks to maintain the soil’s levels. Keep in mind, this process only applies to pink and blue “Macrophylla” varieties.  

Our Favourite Hydrangeas

Here are some of our favourite hydrangeas to grow right here in South Ontario:
Hydrangea Arborescens – “Annabelle” is the most well known of this group. These hydrangeas boast dome-shaped groups of flowers and lovely heart-shaped, floppy leaves.
Hydrangea Macrophylla – Also known as “Bigleaf Hydrangeas,” these classic varieties live up to their name, offering heart-shaped, glossy leaves that are very hardy. They have marvellous, colourful mophead or lacecap flowers that are excellent for colour changing. 
Hydrangea Quercifolia – Known as “Oakleaf Hydrangeas,” these varieties are easy to recognize by their texture-rich, leathery, and oak-like leaves, blooming with cone-shaped flowers. 
Hydrangea Paniculata – Also known as “Peegee Hydrangea,” the most popular variety of this type is “Limelight.” These hydrangeas have iconic cone-shaped flowers that make them easy to identify. 

Hydrangeas are not difficult shrubs to take care of! With a bit of knowledge you can get all the benefits of their gorgeous blooms every year, without risking the frustration of mistakes. These shrubs are so popular because they create long lasting, easy care impact in any yard. For delightful flowers, stunning colour, hardiness, and a little bit of colour-changing magic, stop by the Glasshouse today!

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