My opinion on hydrangeas is always evolving. There’s the snob in me that regards them – especially the mophead or pom-pom varieties – as common, conservative and way too blousy.
They’ve always been there – even in the gardens of people who don’t necessarily like plants or gardening. You’ll not seek them out at a specialist nursery but instead buy them on a whim, picked up on a garage forecourt or market stall, alongside all the other 1970s’ throwbacks. Hydrangeas are a mainstay and a stalwart that can be relied upon to underwhelm.
But then around Lúnasa they will catch my eye – a range of alluring blues or deep reds, and sometimes, somehow, all the subtle pinks, scarlets, aquas and cyans in between.
The hydrangea’s colour palette sounds impossible on paper but against the odds it manages to display half the colour spectrum, occasionally on a single plant, its flowers’ shades dictated by the pH of the soil - blue in acidic soil, red/pink in alkaline.
My preferences are at each extreme, with the washed out colours in between reinforcing the plant’s bland image when they are dominant.
I’m also more amenable to lacecap varieties. Imbued with greeter elegance than mopheads, their flowers are discs of clustered blossom surrounded by florets. Again, the range in colour is extensive and determined too by whether its roots rest in acid, alkaline or neutral soil.
Less common again are ‘panicle’ varieties, which take their name from their cone-shaped plume-like flowers, the dictionary describing a panicle as a “loose branching cluster of flowers, as in oats”.
Notably, unlike the aforementioned mopheads and lacecaps, panicle hydrangeas’ flower colour is much less influenced by soil pH. The flowers mostly turn various shades of pink as they mature through the summer.
Attempting to ensure your mophead or lacecap flowers in your desired colour may yet prove a fruitless task, despite all the books and online advice to the contrary.
There are all sorts of recommended methods, some that sound truly scientific, others that are old wives’ tales. There’s also a host of commercially available feeds and fertilisers that are packaged in the seductive, deep tones of your dream hydrangea.
Yet unless containerised or at least contained, seeking to change the pH of your soil is a bit ambitious. Adding ericaceous compost – ie peat – is a non-starter from an environmental point of view, while it’s also likely to be costly.
Adding sulphate of iron, available from garden centres, is a more sensible and economical option but in my experience has yet to succeed.
One common method that may have some scientific basis is mulching with the contents of used tea bags around the base of the plant to turn pink flowers blue. As tea is made from Camellia sinensis, a plant that’s most productive when pH levels are between 4.0–5.5, this makes perfect sense.
Sounding similarly good in theory is placing rusty nail in the hold as you plant your hydrangea or feeding with a liquid made from soaking nails or other waste metal in water.
The experts argue that hydrangea macrophylla or hydrangea serrata lend themselves better to colour transformation but you probably have to seek those out from a specialist nursery.
