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A Plantswoman’s Guide to Gardening – Tessa Knott – Glenwhan

September 2nd 2019

News from Galloway, South West Scotland

When Mervyn Kessell was last here in the garden at Glenwhan he was very struck by the hydrangeas and how well they blended in with the rhododendrons. Not long after, he suggested I write an article to that effect. This must have been more than a few years ago and I feel now I want to write this to honour Mervyn’s memory.

Hydrangeas are a large family, and to my mind much underrated and under planted in the British Isles. I suspect to some; the word hydrangea conjures up a picture of muddy coloured mop heads poking over white washed walls be the seaside. It is certainly true they are a very good seaside plant, but hydrangeas deserve their place as well in a woodland setting or the smaller garden. The genus comes in all shapes and sizes and is a large and varying family. The species can be roughly divided into three sections: deciduous and shrubby, deciduous climbing and evergreen, and the evergreen climbers and trees. This covers a very wide area, so I will only attempt to sing the praises of some of the plants I know and grow in my own garden.

As with many other plants, we owe a great debt to the different explorers who travelled the world at risk of life and lib driven by the potential reward of standing in rapture before some unimaginably beautiful sight round the next bend in the path. The Japanese grew hydrangeas in their gardens for a very long time without the rest of the world knowing, as foreigners were seen as an undesirable influence. Now, however, we can grow and obtain many different varieties. Outdoor hydrangeas are the late summer glory of favourably situated gardens from the far North West of Scotland to Dover and are a family of beautiful plants flowering late into the autumn until the flower heads finally succumb to autumn frosts. This to my mind makes the hydrangeas invaluable companion plants to the rhododendron.

One such plant is the hardy Asiatic species H. paniculata grandiflora (from Japan and China) with conical ivory flower heads which grow to a length of 45cm. These flower heads remind me more o rather luscious white lilacs. I grow two lovely cultivars, H. paniculata ‘white Moth’ and “Brussel’s Lace’ both which flower in August and continue on for six weeks or more. In the spring these plants look like brown sticks and one would be forgiven for thinking they were dead, but R. barbatum growing nearby takes over at this time and fills the gap with its beautiful bright red flowers. Hydrangeas enjoy similar conditions to those of the rhododendrons (another food reason for planting them) though the former is less fussy as to soil, merely turning a different colour according to the mineral content. The white varieties tend to stay white and here I must mention the lovely H. ‘Madame E. Mouilliere’, a superlative classic white hydrangea which grows in full sunlight or can be grown in tubs without difficulty, thus lightening up the green foliage of a bank of rhododendron.

The beautiful lacecap clonal varieties with their dark fertile flowers at the centre and the sterile florets round the edge (hence the name) all turn a beautiful blue. The visitors in my garden derive much amusement from H.‘Teller’s Pink’ which here at Glenwhan, on our acid soil, becomes a vivid electric blue and is certainly a ‘star turn’ in the garden. These lacecaps in fact will grow trouble free for a great many years with little attention paid to them. Where space permits, and with a certain amount of shelter, I would recommend the stunning species lacecaps, which look wonderful in woodland gardens and blend together with azaleas and rhododendrons and spices roses, particularly H.villosa and H. sargentianawith their large woolly leaves from China. Both these woody shrubs can grow into small tress, and again look nothing in the spring, but give off their best after the rhododendrons have finished their show.

If you fancy something a bit different, what about H. quericifoliawith oak shaped leaves, the only hydrangea to have lobbed leaves. A native of the US, this plant grows to about 4 m. The flowers are creamy-white turning to purplish-pink and to cap it all, the leaves turn a glorious crimson, orange and yellow. For the smaller garden, H. ‘Blue Deckle’ (developed by Michael Haworth-Booth) with small neat heads of powder blue lacecaps in a magnificent plant producing plenty of flowers, being a useful low grower not reaching more than 1.8m in height.

If you are partial to ‘show-offs’, H. arborescens ‘Annabelle’ takes some beating with the huge showy white pouffe-shaped heads that weigh down the delicate stalks. The original species was the first hydrangea discovered in South East USA in 1739. H. manchuricahas attractive dark chocolate stems, and H. maculata boasts showy cream and white variegated foliage with large pale lacecap flowers making a good even sized border subject. This plant may be somewhat tender in certain parts of the country, but it makes a good patio subject where it will get the necessary shelter. If it is a vigorous climber that you want to reach for the sky, and have a north facing wall, H. petiolariswould very well fit the bill.

To conclude, I must lastly mention a little gem, H. serrataf. chinensis. Originally from China, it is a small dense bush and never grows more than 40cm; the lacecap flowers are a beautiful pure pink, which never turn blue even on the most acid soils. This plant is best grown in semi-shade because the root system is very fine and close to the surface.

A few Notes on Cultivation: though hydrangeas may be grown in shade and have the advantage of keeping their colours longer (which allows them to be used to make a lovely arrangement of dried flowers) they may be grown on a south facing slope where the frost runs down the hill. Northern and western positions are preferable while exports to the east should be avoided as late frosts can damage and destroy young shoots. The plants tend to need plenty of water and is another reason why a cool position is preferable. Hydrangeas benefit from an annual mulch of leaves, bracken or fertiliser, as after several heavy crops of flower they can exhaust the nutriment of the surrounding soil.

Finally, I would like to end these jottings with a quote from Michael Haworth-Booth’s book entitled ‘The Hydrangeas’: “The history if this plant goes back a long way. Among the wooded hills and on the shores of Japan, among the beautiful red and black pines leaning picturesquely away from the wind, among the fretted lava rocks or the myriad smoke blue wisteria and the azalea and wild white rose, like a scene in a fairy story the ancestral wild hydrangeas grow.”