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!).
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.
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.
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.
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.
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’.
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.
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.
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.
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.
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.
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’.
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.