hydrangea

The 'Dirt' on Hydrangeas

The 'Dirt' on Hydrangeas

By Jim Hole


Fact or Fiction?
You can change the colour of your hydrangea flowers by making the soil acidic.’

Hydrangeas are some of our most spectacular flowering shrubs. And while there are over a dozen great varieties that grow beautifully on the prairies, there are those among us who just can’t resist the challenge of changing a pink flowered hydrangea to one that flowers blue or vice versa. Today there are over a dozen varieties that we can grow here successfully.

But can one really change hydrangea flower colour? The answer is yes…well, sort of.

Changing the colour of hydrangea flowers starts with understanding a bit about soil chemistry and then choosing the right varieties. In our greenhouses, I was the guy who was in charge of adding the correct ingredients, in the right proportions to the soil half of the hydrangeas would flower blue while other half would flower pink. But I’ll be the first to admit that I didn’t always get it right. More often than I care to admit, I ended up with what are known as ‘blurple’ hydrangeas – mostly blue but with enough red blended in to give the hydrangea flowers a purpley tone. Now, I thought the blurples were rather attractive but, apparently, that sentiment wasn’t shared by everyone!

So how does one get a red, blue or even a blurple hydrangea for that matter? It all begins with choosing hydrangeas that have the capacity to change colour. The vast majority of the hydrangeas that we grow here are incapable of changing colour regardless of what you do. For example, white hydrangeas will remain white regardless of what treatments you provide.

If you have responsive hydrangeas then the next step is to raise or lower the soil pH above a threshold level depending on whether you want blue flowers or pink flowers. If you want a pink hydrangea, the soil must be fairly alkaline (higher pH) but if you want a blue hydrangea the soil must be rather acidic (lower pH).

Diving into soil chemistry just a bit deeper, acidic soils make aluminum (a naturally occurring soil element) more soluble and more readily absorbed by plant roots whereas alkaline soils make aluminum less soluble and thus more difficult for roots to absorb. At the cellular level the aluminum alters the pigments in the hydrangea blooms and, voila, the flower colours change. But the caveat here is that if you don’t tweak the soil correctly, you’ll end up with my blurple colour.

Keep in mind that only a select few hydrangeas are responsive to manipulation of soil pH. In you want to experiment, a variety called Bloomstruck is one variety to have some fun with.

Remember too that once an existing flower is already pink or blue, it won’t change colour. Tweaking soil acidity will only affect the coloration of flowers that have yet to develop.

Also, in the garden, pH manipulation can be very difficult particularly if you have a clay-loam soil with lots of lime in it. Acidifying this type of soil is nearly impossible so just be satisfied with growing a healthy, floriferous hydrangea and enjoy whatever colour you get!

The florist type hydrangeas (hydrangea macrophylla) are the best hydrangeas for having some fun with flower colour transformation. They are only marginally hardy outside but are great for playing around with outside in containers during the summer. They love morning sun but hate intense afternoon sun so place them in a spot where they won’t suffer from sunburn.

Remember that even if you change soil pH beyond certain threshold levels, you won’t get a rainbow colours from your hydrangea flowers. Pink and blue are your only two choices…and blurple, if you weren’t paying attention in your soil chemistry class.

Some great Hole’s Hydrangeas to grow:

  • Annabelle, Bloomstruck, Bobo, Incrediball, Limelight

Training Shrubs to Single-Stem Tree Form

Training Shrubs to Single-Stem Tree Form

Looking to add a distinctive feature to your yard? Try training shrubs into a long, branchless central stem topped with a full head of foliage. With quality plants, the right technique and patience, you can transform your favourite shrubs into dynamic tree silhouettes. Here’s how.

  • Start with a high-quality shrub in a one or two gallon pot and plant as you would any shrub.

  • Examine the shrub and select the largest, healthiest stem. This will become the ‘trunk’ of your tree-form shrub. Prune off most of the other stems, leaving some extra branches untouched for the moment. The extra foliage of these branches will give the plant the energy it needs to grow.

  • Maintain the tree form by pruning off new side shoots so that all of the plant’s energy goes into the remaining stem.

  • Stake and rod the stem to keep it upright. The rod and stakes should remain in place until the selected stem is able to support the weight of the plant.

  • Once the shrub reaches the desired height (1.2 m of clear stem is a good guideline), clip the top to force buds out, and remove any buds on the stem. This is also the time to remove those extra branches you left on the stem for plant growth. Treat like a normal shrub to produce a nice round head.

  • The shrub will continue to produce shoots in unwanted areas. Remove these shoots to maintain the tree form.

Make sure your expectations are realistic—training will not transform a 2-m tall shrub
into a 4-m tall tree, though your shrub may grow a little taller than usual because the
plant’s energy has been redirected to a single, central stem.

You can train almost any shrub, but here are a few suggestions to get you started.

Amur maple
Russian olive
Lilac
Evans cherry
Ninebark
Potentilla
Dogwood
Hardy roses
Hydrangea
 

Multi-Stemmed Tree Forms

Many large shrubs can be trained to multi-stemmed tree forms of three, five or seven
stems. Russian olive and amur maple look beautiful when trained to these forms.

Buying Tree-Form Shrubs

If you like the look but don’t feel like doing the work, you can buy mature shrubs in tree
form. Some of these shrubs are trained to tree form (dogwood, potentilla, ninebark, hydrangea), while others are created by grafting a shrub such as lilac or caragana to a
compatible rootstock. Note, however, that grafted tree-form shrubs are generally easier
to maintain than trained tree-form shrubs, as the rootstocks are chosen both for height
and their tendency to avoid creating side shoots. Grafted tree form shrubs come in a
variety of heights. In some cases, the central stem may be a metre tall, in others only
half that. It all depends on what the grower has chosen.

Moon Garden

Create a Nighttime Garden for the Senses


A nighttime garden is a magical place filled with unfamiliar murmurs and inviting
fragrances—the perfect place for rest and retreat. At the end of a workday, there
may be little time to spend in the yard before dusk, so it just makes sense to plan
a garden that comes alive in the evening. The best of these gardens play to our
sense of sight, scent and sound. Softly lit shadows, fragrant night air, musical
dark water. With a few thoughtful choices, you too can create a space that
functions as well in the evening as it does in the day—all it takes is a little night
magic.


See the Night
Many of the features that turn a garden into a place of nighttime splendour will
also improve its daytime beauty. Luminous whites, silvers and creams reflect the
moonlight and contrast dark foliage, giving your eyes a reprieve from the pinks,
blues and yellows that populate most flowerbeds. Two perfect examples are
‘Incrediball’ hydrangea and ‘Affinis White’ nicotiana. Both have striking blossoms
and architecture that would enhance any garden, but at night, they stand out
from the shadows and create luminous points of interest.


The lemon yellow blossoms of this evening primrose (Oenothera macrocarpa)
open at dusk, making this perennial an ideal choice for a nighttime garden. For
best results, give this plant a home in a sunny rock garden with good drainage.
Height: 15–30 cm; width: 30–50 cm. Sun. 
Incredibly large ball-shaped flowers are the hallmark of this new variety of
hydrangea arborescens. ‘Incrediball’ is a hardy hydrangea bred to have sturdier
stems and larger blooms than the similar-looking and ever-popular ‘Annabelle.’
Spectacular, late-summer blooms emerge lime green, mature to white and then
age to a darker green. Given sufficient moisture, this shrub will tolerate full sun.
Height: 60–100+ cm; width: up to 1 m. Shade to A.M. sun.

Nicotiana is known for its
jasmine-like scent, but it’s this
variety’s white flowers that will
capture your attention in the
moonlight. ‘Affinis White’ blooms
continuously throughout the                                                                                                summer, providing a plethora of
trumpet-shaped flowers with which
to tempt the senses of both
gardeners and hummingbirds.
Height: 90–100 cm; spacing:
25–30 cm. Sun to P.M. sun.


Lighting Made Easy
There are numerous ways to supplement moonlight in the garden. Here are a
few of our favourite options.
• Solar lighting: A few well-placed solar lights will cast a subtle luminescence on
your garden. Because of its recent popularity, solar lighting can be found in
every style from path lights that oscillate a kaleidoscope of colours to
traditional carriage lights and whimsical paper lanterns. All are fantastic
options.
• Electrical lights: String lights are ideal for adding a twinkle to evergreens or the
rooflines of gazebos. Spotlights are ideal for highlighting a central garden
feature, such as a fountain, pond or statue.
• Candlelight: Little else can compete with the flickering glow of candlelight.
However, to keep your garden safe as well as beautiful, you should house
your candles in lanterns or other lidded vessels.


Quick tip
Create a nighttime focal point that’s visible from your window. This way, you can
enjoy your garden even on nights when the weather keeps you in.


Breathe the Fragrance
Our senses come alive at night, so there’s no better time to experience the sweet
fragrance of flowers and the pungent scent of evergreens. Evening scented stock
are traditionally a favourite, but more unusual options, such as brugmansia
(Angel’s trumpet), should not be overlooked. To bring those fragrances indoors,
simply plant aromatic annuals near a frequented doorway or an open window.


The gorgeous fragrance of evening scented stock more than makes up for
this plant’s unassuming nature. Pale mauve flowers fill the night air with a vanilla
and nutmeg scent that can best be described as irresistible. Their airy
and unkempt growth habit is best suited to mass plantings or the middle of
borders where shorter plants can disguise their bases. Height: 35–40 cm;
spacing: 10–15 cm. Sun.
 
If vanilla-scented mounds of lacy flowers are your thing, then heliotrope is your
plant. Its upright habit makes this annual perfect for framing the edges of borders
or filling out pots and window boxes. Height: 30–35 cm; spacing: 25–35 cm. Sun.
 

Merely brush past a container of petunias in the evening, and you’ll instantly
know why they belong in a nighttime garden. Few other plants perform as
exceptionally as petunias, but it’s their heady fragrance that makes these
annuals stand out in the evening. ‘Midnight’ (from the Madness series) is a
particularly beautiful shade of purple. An old favourite for good reasons. Height:
25–30 cm; spacing: 15–20 cm. Sun to P.M. sun. 


Take an evening stroll through a
patch of woolly thyme (Thymus
pseudolanuginosus) and be
instantly refreshed by the earthy,
herbal notes it releases. And
don’t worry about the thyme
because it can withstand light
foot traffic. The grey-green
foliage of this perennial is
covered in bright-pink blooms from
late spring to early summer.
Drought tolerant. Mat forming.
Height: 1–2 cm; width: 30–45+ cm.
Sun to P.M. sun. 


For a sense of drama that’ll keep you smiling, add brugmansia to your patio or
garden. This massive annual has impressive trumpet-like flowers that are up to
30 cm long. During the day, the large leaves of this towering plant do a great job
of filtering light. During the night, the fragrance from its sweet-scented flowers fills
the air. Height: 1–2 m. Sun. 


Hear the Night Music
Each fountain, brook or waterfall has a sound and charm unique to itself.
Selecting a fountain that’s music to your ears will often mean finding a
fountainhead that generates the sound you like. Fortunately, there are almost as
many styles as there are gardeners. 
Whispering in the softest breeze, the elegant blades and seed heads of feather
reed grass (Calamagrostis x acutiflora) will create sound and movement in your
nighttime garden. ‘Avalanche’ is a particular favourite on the prairies for the
interest its towering blades add to the wintery landscape. This clump-forming
grass tolerates poor soils but performs best with good moisture. Height:
90–150 cm; width: 30–45 cm. Su
n
Finding wind chimes you’ll want to listen to on a regular basis can be as
difficult as finding a radio station for your daily commute. However, when you do
find the right fit, you don’t want to be without it. 


Garden Frogs 101
Frog calls have their own magic. With diminishing global frog populations, many conservation groups are encouraging gardeners to create urban frog habitats.
• If you wish to attract frogs to your garden, you’ll need a body of water with
sloping sides. At least part of the water should be shallow; frogs prefer shallow
water for laying eggs.
• Algae is a vital food source for tadpoles, so a frog pond should be partly
shaded (to keep the soil moist) and partly sunny (to increase algae production).
• Frogs do not mix well with fish, so if you have Koi or Gold Fish, you’ll have
difficulty attracting frogs.
• Provide shelter and shaded areas in the form of rocks, shrubs and low-
growing plants.
• Be aware that, although enchanting at a distance, frog calls can become quite loud during breeding season. You may not be popular if your frog habitat is located close to your neighbour's bedroom window.


Did you know?
Frogs are nature’s pest control experts. Frogs eat slugs, cutworms, mosquitoes, earwigs and various beetles.