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Growing hydrangea – a Master Class

Jennifer Stackhouse

Jennifer Stackhouse

April 22, 2014

I am sure my love for hydrangeas is part of my genetic make up, even though they are disparaged by some as ‘nanna plants’, and others see them as water wasters. I don’t agree with either view, although my Nanna was responsible for my love of these fabulous summer-flowering shrubs. I’ve also discovered that hydrangeas are facing a very 21st century problem (read on for more on this!).

The hydrangea blues

Hydrangeas were a great favourite of my Brisbane grandmother (Norma Howes, my Mother’s mother) and stars of her summer garden. I vividly remember as a child picking them to use to decorate the house for Christmas and learning about plunging the cut stems into a bucket of water to keep them from collapsing and all about smashing the base of the stems so the flowers wouldn’t wilt.

Watch out for powdery mildew on hydrangea

As well as being a gardener, Nanna was an artist and a potter and hydrangea flowers and leaves featured in her work.

When we moved from Brisbane to Sydney I found myself in hydrangea heaven. We lived in Neutral Bay and Mosman, Sydney suburbs noted for their summer displays of blue hydrangeas.

Hydrangea expert
But hydrangeas don’t have a large fan base, so I was delighted to hear that one of the most hydrangea-passionate people in the world was visiting Australia to talk at the Collectors’ Plant Fair.

One f the many questions for Mal Conlon at the Collectors' Plant Fair 2014

One of the many questions for Mal Conlon at the Collectors’ Plant Fair 2014

Mal Condon has one of the largest collections of hydrangea varieties in the USA and firmly believes that the east coast of Australia and particularly Sydney is an ideal place to enjoy the magic of hydrangeas. His motto is

“There’s always room for one more hydrangea in your garden”.


Mal, with wife Mary Kay, owns Hydrangea Farm Nursery at Cape Cod in Massachusetts on the USA east coast in a region with cold winters and mild summers. They recently relocated the nursery from Nantucket Island to the mainland at Cape Cod. Although not a trained horticulturist he is passionate about hydrangeas and has grown and collected them for nearly 40 years.

Hydrangeas on display - all from Don Schofield’s garden at Mount Tomah

Hydrangeas on display – all from Don Schofield’s garden at Mount Tomah

For much of its life the nursery specialised in the growing and selling of large hydrangea plants but, following what Mal described as the trend in the US, he has shifted the business to growing and selling smaller plants with most sales now via the internet rather than from personal shoppers. He also gives workshops and is a regular at plant fairs in the US where he markets himself as a ‘collector’s nursery’.

Hydrangeas at the Collectors' Plant Fair

Hydrangeas at the Collectors’ Plant Fair

In his talks at the Collectors’ Plant Fair in April Mal made valuable comments about hydrangeas and particularly about growing them in 21st century Australia, which I thought would be of interest to GardenDrum readers.

Hydrangea 'Snowflake'. Photo Peta Trahar

Hydrangea ‘Snowflake’. Photo Peta Trahar

He noted that hydrangeas growing in his Nantucket garden tend to be smaller, more compact plants with more flowers than the plants he was seeing in Australia and New Zealand. He put this down to the cold winters on the US east coast. The milder summers also mean that he grows hydrangeas in more direct sun than they are grown here. He has also found that constraining the roots (for example in a container) can lead to increased flowering in some varieties.

The role of UV light
But the story doesn’t end there. For Mal the big difference between growing hydrangeas in the northern and southern hemispheres wasn’t the summer or winter climates or even the latitude, but the amount of UV exposure in our part of the world. Basically the extreme levels of UV that cause us to have high rates of skin cancers are very damaging to hydrangeas especially their flowers.

To get the best from hydrangeas Mal recommends a position with an easterly aspect with shade for the rest of the day. I would add to this a southerly aspect with shade from the late afternoon sun in summer. If this protection is given to the plants, they’ll flower without summer burning. Mal recommends companion planting to provide the necessary shade.

Hydrangea 'Direktor Kuhnert'. Photo Mal Conlon

Hydrangea ‘Direktor Kuhnert’. Photo Mal Conlon

Where sun exposure is inevitable he suggests selecting varieties that have the combination of shiny leaves and dark flowers such as ‘Direktor Kuhnert’ as these varieties have great sun tolerance.

Australian varieties
Mal’s other revelation was that there are varieties in Australia not grown anywhere else. He believes some to be Australian selections or sports and others to be heritage varieties lost from cultivation elsewhere.

One that he was very excited to discover here in Australia (in Peta Trahar’s Woodgreen garden at Bilpin west of Sydney) was a green-flowered form called ‘Green Mantle’. He also mentioned that he considers ‘Aeysha Superior’, ‘Caroline’, ‘Ne Plus Ultra’, ‘Prince Henry’, ‘Snell’ and maybe ‘United Nations’ are unique Aussie varieties.

Hydrangea 'Green Mantle'. Photo Peta Trahar

Hydrangea ‘Green Mantle’. Photo Peta Trahar

Top tips
Mal had lots more good advice. Here’s some of what he told us about growing hydrangeas, particularly Hydrangea macrophylla.

Fertiliser: Hydrangeas have low fertiliser needs but benefit from an application of slow-release fertiliser with micronutrients in spring. He recommended a low phosphorus fertiliser for blue hydrangeas.

Small fertile flowers are in the middle of petal-like bracts

Small fertile flowers are in the middle of petal-like bracts

Pruning: He recommends a seasonal approach to pruning Hydrangea macrophylla and reminded us it was part science and part aesthetics. Hydrangea macrophylla flower on old wood in early summer.
1. Mid summer: In mature plants, prune non-flowering and burnt blooms before February 1.
2. Autumn: Deadhead.
3. Late winter: Remove spent flowers cutting back to first pair of live buds. Also at this time hard prune old stems. The maximum life of a stem is five to six years. Take out ageing stems (identified by exfoliating bark) to ground level to rejuvenate plants and let in more light.

Repeat flowering: Some newer varieties are repeat flowering (for example Endless Summer forms). These flower from summer to autumn with flushes of blooms. Some older varieties also repeat flower including ‘Penny Mac’ and ‘Nikko Blue’.

Hydrangea 'Prince Henry'. Photo Peta Trahar

Hydrangea ‘Prince Henry’. Photo Peta Trahar

Soils: Make sure soil has good aeration and is free draining with high organic content.
pH Flower colour of H. macrophylla varieties responds to aluminum content of soil (usually related to soil pH) with the best pH for blue sitting at 5.2-5.6 and for pinker tones 6.0-6.5. Apply aluminium sulfate as a drench at a rate of 2 tablespoon per 9-litre watering can applied twice per season to ‘blue’ up hydrangeas or add dolomite lime to raise pH.

Wetting agents: Highly recommended. Mal admitted that his plants grow in very sandy soil in Nantucket.

For more of Mal’s hydrangeas see his website Hydrangea Farm and for more on Hydrangea ‘Green Mantle’ see Peta Trahar’s storyFalling in love with hydrangeas again’.

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9 years ago

I think the late Joan Arnold held the Australian collection of hydrangeas. Would love to know what happened to her collection. Does anyone know?

Peta Trahar
9 years ago
Reply to  Paul

Hi Paul. As far as I know, Joan offered Don Schofield everything she had of the National Collection because she wanted to be sure that it would not be lost when and if she moved from her garden. This was several years ago. Over the years Don has added more to this collection, now planted in his beautiful garden at Mt Tomah. It was Don who introduced Mal Condon to us and suggested that he would be perfect as a presenter at the Collectors’ Plant Fair. Judging by the interest Mal has stirred up it was the right time to feature Hydrangeas. I for one have really started to build up more species in the garden. A couple of weeks ago, Don and Mal visited another gardener in Victoria who has maintained an excellent collection so thank goodness, looks like the genus is in good hands and on the brink of a real resurgence.
Cheers, Peta

Jennifer Stackhouse
Jennifer Stackhouse
9 years ago

Thanks for the update Peta.

Peta Trahar
9 years ago

Oh, I should also remind everyone that the 10th Collectors’ Plant Fair will be held again at Clarendon on 11/12 April 2015. http://www.collectorsplantfair.com


Libby Cameron
Libby Cameron
9 years ago

Thanks Jennifer for such an informative article, as I was unable to attend the Hydrangea talks at the wonderful Collectors Plant Fair. What a great event that is, thanks to you and your helpers, Peta. I am enjoying my hydrangeas more than ever at my new home, and I guess that must be because I have so many grandchildren. I am looking forward to adding a few interesting hybrids to the ones that came with the house! We have struggled with moving a few large plants that were being burned by the westerly sun, mainly because of our very dry spring, but I am sure next year they will take off.
Wonderful plants, and so indicative of Sydney summer!!