Rehydrating the Hydrangeas

Sunday, 29 November 2009

Mopheaded Hydrangea macrophylla

The awful heatwave conditions over the past few weeks have taken a bit of a toll on my Hydrangea shrubs: they wilt tragically in the onslaught of the hot days. However, I have noticed that they have bounced back pretty well once the temperature cools down, as long as they get some water during the hottest times.

Hydrangea macrophylla Tosca

Plump Hydrangea bushes, with their bold blue or pink mopheads, were part of the landscape of my childhood. Everyone grew them, including my parents, who had a row of them on the southern side of our house where we would play on hot days. When I first started gardening, I spurned them as 'too common', but eventually I realised that they are wonderful plants for our Sydney climate, blooming over an extended period from late spring through summer, and being attractive even as their flowers age in autumn. The fact that they enjoy shady parts of the garden is an added bonus. They provide excellent cut flower material as well: pick the stems in the early morning and keep immersed in a bucket of water, up to the flower heads, for several hours before arranging in your vase. Stems picked in autumn can be dried to provide a long-lasting floral display. Remove the leaves then keep in a vase of water until the flowers become like paper.

Hydrangea macrophylla Lanarth White in the garden of Pamela and Harry Fowell in Sydney

It's true that Hydrangea can look hideous and straggly if they are neglected and unpruned, but as long as they are given some water and a bit of attention, they will reward you many times over. Their need for water can be reduced somewhat by planting them from the outset in good, compost-enriched soil and keeping them well mulched. Once they are established, they need less watering. It is best not to plant them too near to large trees with greedy roots - they grow best in the shade cast by buildings where there is no root competition. They don't mind having some morning sun - and in fact will flower better for it; it is the hot afternoon sun that will singe their leaves and burn their blooms. Refer to my plant directory entry for Hydrangea macrophylla to see more cultivation details.

Hydrangea macrophylla Libelle in the garden of Pamela and Harry Fowell in Sydney

The status of Hydrangea macrophylla has risen in recent years, with many fancy cultivars now available. The big domed mopheads are the most commonly seen - all mine are cuttings of the ones once grown by my parents in their mountains garden, with no identifiable names. The pretty lacecap varieties, with an outer ring of sterile florets surrounding a clustered centre of tiny fertile flowers, are very popular with gardeners at the moment. Reliable cultivars include 'Libelle' (ht 1.5m) and 'Lanarth White'( ht 1.5m), both with white florets. Coloured ones are also available. I have a variegated-leaf lacecap originally grown by my grandmother in her garden for many years (possibly H. 'Maculata').

Hydrangea macrophylla Ayesha

I also have an unusual Hydrangea macrophylla cultivar named 'Ayesha', which is a very strong, tough shrub, growing almost 3m tall. I received it as a cutting from my old neighbour the day I left my previous home in Ryde. Each flower has a cupped, waxy form, a bit like a lilac - our local florist refers to it as 'popcorn Hydrangea', and each flower-head does actually look like a cup of blue (or pink!) popcorn! Hydrangea flowers vary from pink to blue depending on the pH of the soil - an acid soil results in blue flowers, whilst an alkaline soil gives pink blooms. I have one cultivar called 'Tosca' (pictured earlier in the blog) which is said to always stay pink because it doesn't take up the aluminium in the soil, but even that one has been known to turn blue. White forms are stable. There are red ones available - I'm not sure how these fare in different soils. Various substances are available from nurseries to manipulate the colours. On the whole, the intensity of the flower colour in any particular cultivar doesn't change a lot: some are naturally pale and others more strongly coloured. There are forms which have double flowers, which are intriguing and attractive. Hydrangea heights vary from 1 - 3m; many of the smaller Hydrangea can be grown in pots.

?Hydrangea Maculata

Their large, lush green leaves provide an effective backdrop to other plantings. I think they look best when massed together, rather than grown on their own. In the long shady border where my Hydrangea bushes are, I also grow Japanese windflowers, renga renga lilies, Solomon's seal, arum lilies, Plectranthus species and variegated honesty. Other options are shrubby or cane Begonia, Justicia carnea, Acanthus mollis and ferns. My border only needs attention for a few hours a year and always looks OK - my own oasis of coolness like the one remembered from my childhood.