IN THE GARDEN: THE SHRUB QUESTION
An important layer: These plant stars add structure, foliage interest and colour with careful planning
When you build a garden, you need to think in terms of four key levels of content.
At the top, occupying the skyline, is the tree-canopy, so you naturally need to think of what trees to plant, both tall ones and smaller- and medium-sized ones to create this billowy barrier of foliage. At the bottom, literally at ground level, is the perennial layer, consisting of various hardy herbaceous and semi-evergreen perennials that create a natural sequence of flower and foliage interest.
Below this layer — the subterranean level — is the garden’s bulb content; snowdrops, crocus, daffodils, tulips, erythroniums, alliums and so on. It took me a long time to realize just how important this hidden, below-ground level is to the overall quality and look of a garden. Today, I have no doubts about how vital the bulb/corm/rhizome/tuber content is.
But in between the upper tree canopy and the basement levels, there is the immensely important shrub level.
Many people think this is actually the only plant level. It is often all they see when they walk into a garden — shrubs rubbing shoulders with one another and taking turns to produce either great flower displays or wonderful foliage colour.
Some may argue that shrubs are indeed the true plant stars and the key centre stage acts of any garden and everything else, including flowering bulbs and herbaceous perennials, are just fill-in performers, creating diversion between the main events.
So the big question for many gardeners at this time of year — the start of spring — is which flowering shrubs to plant for reliability, long flowering, hardiness, disease resistance and overall esthetic excellence.
In the first light of spring, when snowdrops and crocuses pop into flower, it is also good to have some fragrant shrubs in bloom.
Sarcococca (sweet box) is a must-have, as it not only tolerates shade and has superb evergreen foliage but also puts out tiny white flowers with a pleasant, pungent scent.
For a sweeter perfume, there’s Daphne odora, considered one of the most fragrant of all springflowering shrubs. It produces clusters of super-scented pink flowers in March.
Some experts regard Daphne bholua ‘Jacqueline Postill’ as superior, but it is also less compact. You also can find a variegated kind called ‘Aureomarginata’. These are worth planting close to a path or entrance.
Another first-class daphne for foliage interest and fragrance is ‘Carol Mackie’, a tough, problem-free shrub that also grows to about 1.2 metres (four feet).
Hummingbirds love red-flowering currant (Ribes sanguineum) and this is also a beautiful shrub for early spring with its attractive pendulous clusters of rich pink-- red flowers set against newly emerged dark green leaves. ‘King Edward VII’ is a star cultivar, but ‘Pulborough Scarlet’ is famous for its cardinal red flowers. Both look terrific with a carpet of hellebores, snowdrops and crocuses underneath.
Viburnums are a group that can’t be ignored. V. bodnantense ‘Dawn’ is a late-winter bloomer, noted for its intense fragrant pink flowers, but the Korean spice viburnum (V. carlesii) is a better long-term choice. Excellent picks for flowers in latespring/early summer would be ‘Summer Snowflake’, ‘Mariesii’ and the snowball bush, V. opulus ‘Sterilis’.
Without question, the most important foundational shrub in coastal gardens is the rhododendron. It’s a mistake not to have a collection of these in your garden of various sizes, both for the beauty of the flowers but also for the reliability, structure, foliage architecture and consistency they provide.
Pay attention to size at maturity when you buy plants and focus as much on the shape and texture of leaves as much as size and colour of flowers. You won’t go wrong with yakushimanum hybrids, such as ‘Ken Janeck’, or williamsianum hybrids, such as ‘Bow Bells’.
Evergreen azaleas are indispensable, growing into neat, compact bushes that tolerate being shorn into globes and other shapes. ‘Hino-crimson’ is popular along with ‘Girard’s Crimson’ and ‘Girard’s Fuchsia’. You can dot these throughout your garden, or use them to create a tapestry of colour.
Camellias are less popular today than they once were, partly because of being prone to mildew and weevil problems, but also because the flowers are often damaged by rain or frost. However, when they are well located and can flower without interference they can be spectacular.
Some gardeners like the winter blooming sasanqua-types, others prefer tried-and-tested springblooming japonica varieties. You’ll find C. williamsii cultivars very reliable, notably ‘Donation’, ‘Brigadoon’ and ‘J. C. Williams’.
Skimmia japonica ‘Rubinetta’ is one of my favourite shrubs. I like its compact form, red-green colour in spring and fragrant white flowers. I’m a fan, too, of photinia for similar reasons: being evergreen; easy to prune and shape; and having striking spring colour with bright new red leaves against green older leaves.
Pieris japonica is another evergreen shrub widely used in coastal gardens and loved for the profusion of lily-of-the-valley-like white or pink flowers it produces in March and April. ‘Valley Fire’ is a winning cultivar along with ‘Valley Valentine’ and ‘Valley Rose’.
The key to placing all these shrubs is to think carefully about size at maturity — both height and width — as well as flowering times to avoid colour clashes and to achieve a more even blooming sequence.
Spirea has beautiful foliage colour in spring, particularly ones with lime green, amber, gold and orange leaf tones, such as ‘Magic Carpet’, ‘Goldmound’ and ‘Goldflame’. The classic white bridal-wreath spirea (S. vanhouttei) seems to have gone out of fashion, probably because of its size as it can sprawl to a massive 2.4 to 3 m (eight to 10 feet).
The same is true of forsythia, which is still a fantastic earlyblooming shrub with beautiful yellow flowers, but unless it is pruned routinely every spring, it can quickly grow out of bounds and become a problem. The worst mistake with forsythia is to plant it too close to an early blooming cherry tree — the competition between the vibrant pink and yellow flowers can be a jarring clash.
Enkianthus campanulatus has superb clusters of tiny bellshaped flowers in late spring. I love this shrub so much, I planted two side by side. ‘Red Bells’ and ‘ Showy Lanterns’ are two top cultivars, and there is a white version if you can find it.
Lilacs bloom in May and are widely loved for their beauty and fragrance. French hybrids of Syringa vulgaris are highly rated, but one of the best kinds for coastal gardens is the disease-resistant, more compact dwarf Korean lily ‘Miss Kim’, which produces pale pinky-purple flowers.
Mexican orange blossom (Choisya ternata) is a reliable evergreen shrub, especially for sunny sites because of its tolerance to heat and bright light. It is also universally loved for its scented white flowers in late spring.
Once you’ve completed the composition of your garden’s foundational shrub content, you can add some specialties such as false spirea (Sorbaria sorbifolia sem), a beautiful deciduous foliage shrub, that looks particularly attractive when it first leaves come out. If you have a warmer, protected spot, you could try adding some pittosporum, exochorda and ceanothus but I have had no luck in my zone 7 garden. Hardiness barriers are always worth challenging, so don’t be afraid to a try few shrubs with a more cold-sensitive streak.
Next, you need to think about summer-flowering shrubs, including ones that bloom from late-summer into fall. But that’s another story.