Shamrock

The world's most complete collection of hydrangeas is a hidden jewel on the picturesque coast of Upper Normandy.

10/22/2001
Shamrock
Hydrangeas are the signature plant of the country landscapes of Upper Normandy. From June until frost, virtually every home--from thatched cottage to lordly chateau--is smothered in a profusion hydrangea blossoms. Blooming with a luxuriance that has to be seen to be believed, their flowers of pink, blue, lavender, rose, violet, and every nuance in between weave a rainblow of color throughout the region.

Shamrock, a garden dedicated to the study of the genus Hydrangea, was founded just outside the charming village of Varengeville sur mer by Corinne and Robert Mallet. Robert's (pictured above) family has lived for generations in Varengeville. His family estate is the stunning nearby landscape park, the Parc du Bois des Moutiers, which was created in a collaboration among Edward Lutyens, Gertrud Jekyll, and Robert's grandfather, Guillaume Mallet. But that's another story.

Robert, the third generation of his family to be impassioned by plants, hired an energetic young woman to help him in the nursery he had many years ago. His new employee, Corinne, soon impressed him with her knack for plants and her ability to retain an astoundingly encyclopedic knowledge about every cultivar in his nursery. Corinne became fascinated with hydrangeas during this period, and soon her obsession became a shared one. The couple married, and dedicated their lives to the collection, study, breeding, and taxonomy of hydrangeas in a garden they called "Shamrock."

Shamrock existed in its first incarnation (Picture 1 below)on a small piece of rented property near Robert's family park. But a couple of years ago, the couple finally located a property nearby that was suitable to the larger and permanent garden they envisioned. They bought it and embarked on the gargantuan task of clearing the indigenous blackberries from the land, preparing the soil, and with the help of a crew of 15, moving the hydrangeas of Shamrock to their new home.

The new garden just completed its first season. The more than 700 species and cultivars of hydrangea are arranged in beds that are fanned over a gentle south-facing slope like the veins in a giant leaf. Each main bed has features the hydrangeas of a particular nationality of introduction or origin, such as French, Japanese, German, etc. Robert and Corinne have planted giant-leafed empress trees (Paulonia tomentosa) throughout the beds to shelter the hydrangeas and help maintain high humidity in the beds.

Because the hardiness of hydrangeas is a problem for gardeners in USDA Zones 5 and northward, I specifically asked Robert and Corinne to recommend cultivars and techniques for gardeners in regions with severe winters. (The Shamrock garden is located in the Seine-Maritime region of France, which has a climate roughly equivalent to that of coastal Washington state in the U.S.)

Their first answer was of course to grow the extreme hardy cultivars of H. paniculata, which is suitable for USDA Zones 3 through 8. The panicle hydrangea is a large shrub that begins blooming in mid to late summer. Thanks to the De Belder family of Belgium, this species has seen a proliferation of wonderful new cultivars including 'Unique', with snow white flower panicles that are much lacier and larger than those of the old standby, the PeeGee hydrangea. Also introduced by the De Belders is 'Pink Diamond,' a large-flowered selection whose florets turn a deep pink as they age, a characteristic that varies with weather and temperature patterns.

A recent introduction by Pieter Zwijnenburg Jr. is 'Limelight', with rounded blossoms of almost exclusively sterile florets that are a soft creamy chartreuse that contrast wonderfully with lavender pinks as well as violet-blues.

'Pink Fantasy' is a brand new introduction with large conical flowers tinged pink that is remontant, meaning it goes through more than one bloom cycle per growing season. And 'Big Ben' (Picture 2 below) has enormous lacy elongated panicles that swoop gracefully and age a delicate pink.

If you're a gardener lusting to grow blue or pink lacecaps or mopheads (also known as "hortensias") in the north, Robert and Corinne stress that the tribe of H. serrata is in general hardier than the better-known H. macrophylla. You can recognize the serrata types by the matte surface of their leaves as contrasted to the glossy foliage of the macrophyllas. Although most serratas are lacecaps, with a ring of larger sterile florets surrounding a center of fertile florets, H. serrata var. yezoensis (Picture 3 below) has entirely sterile, mophead flowers of blue to pink. Not only is it hardy, but it flowers on new wood and is remontant.

If you're a northern gardener, you may have noticed that your H. macrophylla plants die back to the ground each year, or nearly. Because most cultivars of this species only flower on the previous year's wood, this means that if the plant freezes back, you've lost all the next year's flowerbuds. Robert stresses that even a small amount of frost protection can prevent this from happening. He encourages you to plant your hydrangeas in a wind-sheltered spot, as icy air currents are anathema to hydrangea flower buds, rapidly drying them out. He also points out that the overhead shelter of tree branches, preferably evergreen or with winter-persistent dry foliage (like oaks and beeches) provides a surprising degree of protection.

And here's the lowdown on hydrangea color. Most (not all) serrata and macrophyllas will change from pink in neutral or alkaline soils to blue in acid soils (See Picture 4 below). But there's a bit more to it than that. It's actually the hydrangea's ability to take up aluminum that determines the blue color. Aluminum is unavailable (like iron to acid-loving rhododendrons) to hydrangeas in alkaline soils. But unlike iron, aluminum is not always present in soils. If your soil is aluminum-poor, your hydrangea may remain obstinately pink even if you acidify its bed. In this case, use aluminum sulfate, but sparingly, as too much aluminum is toxic.

The second point of confusion in growing hydrangeas is correct pruning practice. The paniculata types should be pruned right after the blooms fade. Left unpruned, however, they will suffer no worse fate than retaining the unsightly skeletons of the old flowers the next year. Macrophyllas and serratas, however, are more likely to rebloom if the spent flowers are pruned off at the first pair of viable buds (usually the second pair) below the flower. This practice also minimizes the occurence of botrytis blight of the flowers, that unsightly condition where part or all of the blossom turns brown in midbloom. Under no circumstances should these two types be pruned more severely than that as doing so will remove potential flowerbuds.

Learn more about the incredible world of hydrangeas by visiting Shamrock yourself. If you're lucky enough to live in a mild climate, you'll discover many new species of rare beauty and strong flowering power. And northern gardeners will find the best of the hardiest. Either way, the garden in July and August offers a breathtaking tapestry of color. And there are many other spectacular gardens to visit nearby.

Collection des Hortensias "Shamrock"
Route du Manoir d'Ango
76119 Varengeville sur mer
FRANCE
Tel: 02.35.04.02.33
Fax: 02.35.85.30.20
Email: Jacoll@compuserve.com
http://ourworld.compuserve.com/homepages/Jacoll
Open every day except Tuesday from July 1 through September 15 from 10 a.m. to 12 noon and from 2:30 p.m. to 6 p.m.
Entry: 30 F; children under 15 free.

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