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Hydrangea Sensations
Centre of the City, Toronto, March/April 2006.

Looking for a shrub that will have some interest all year long? Consider adding hydrangea to your garden. Lush and lovely through the spring, it produces magnificent bloom through the summer. As a bonus, the flower heads stay on the plant throughout winter, if you allow it.

Hydrangeas range in height from one meter to over 20 meters, so read the label before you buy, to get the right fit in your site. Hydrangeas are often classified by the type of bloom they produce. Mopheads produce blooms that form a large globe. Lacecaps produce a flatter bloom with a lacier effect. The paniculata family produces blooms in a panicle or spike.

There are over 1200 varieties of hydrangea, which can be narrowed down into just a few categories for our area:

- Hydrangea macrophylla – Big Leaf Hydrangea - may be mophead or lacecap
- Hydrangea serrata - Sawtooth Hydrangea - a sub-species of macrophylla
- Hydrangea quercifolia – Oakleaf Hydrangea – with oak-like leaves that turn crimson in fall
- Hydrangea arborescens – Annabelle Hydrangea – the native hydrangea
- Hydrangea paniculata – Panicle Hydrangea - including popular Peegee and Limelight varieties
- Hydrangea anomala petiolaris – Climbing Hydrangea

Most of the coloured hydrangeas we see are of the macrophylla species. Colour is confined to the range between red and blue and varies depending on soil acidity. In very acid soil, flowers are blue, while in less acid soil, flowers may be purple or mauve in colour. If soil is neutral, colours are red or pink. Contrary to popular opinion, it’s not the acidity that affects colour; it’s the aluminum in the soil that can only be absorbed by the plant under acid conditions.

According to Agriculture Canada, Toronto is in zone 6. When buying hydrangea, check that it is rated to over-winter in our area. If you’re thinking about planting hydrangea at the cottage, check the hardiness zone on the web. Remember that deer seem to like macrophylla and arborescens best for snacking.

In general, hydrangeas like moist, well-drained soil. Due to the size of bloom, the stems can bend and break if exposed to strong winds, so a sheltered location is best, or plan to stake them They enjoy mid-day shade, but like direct morning or late afternoon sun. Dappled woodland shade would be ideal. A soil enriched with organic matter, and mulching is a good idea to conserve moisture. If your hydrangea doesn’t flower, it’s usually because of frost or winter damage, pruning too late, or too much nitrogen. Fertilize once in early spring, and again in early fall.

Most macrophylla and quercifolia varieties bloom on last year’s wood, so take care when cleaning up in spring that you don’t snip off all the buds. Prune arboresecens and paniculata varieties in early spring as they bloom on new growth. They will respond to this pruning by sending out new growth and flowers. Renewal pruning (removing 1/4th of the old wood at the base) is suggested on an annual basis. Trim winter damaged shoots to new growth and remove old flower heads in spring.

This Easter, you may be lucky enough to receive a hydrangea. Most gift plants are not meant for the garden, and for most people, the life of the plant indoors enough. But if you just can’t abide to lose it, why not try setting your potted hydrangea into the garden once danger of frost is past. You might actually end up with a handsome new perennial shrub in your yard.

Helen Kirkup
HMK Consultants
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Also by Helen Kirkup:
The Kirkups: Pioneers & Travellers
Available now on