Thorny Problems

The essential evergreen backbone This week: how to prune mopheads; curb an invasive weed; and plan for next spring

Some of the old gardening rules – “only plant in groups of three, five and seven” and “don’t prune your box hedges on Derby Day” – belong to a different gardening era, when people strove endlessly for perfect lawns, and wild flowers were all “weeds”. But one rule holds good still and applies to even the most modest outdoor space: in order to give a garden structure and winter interest (not to mention masking “unsightlies” and filtering the wind), a third of garden shrubs should be evergreen.

FOR SMALL GARDENS

Small, clipped evergreens do not have to be box, with its bad reputation (blights and defoliation by box tree moth caterpillars). There are box lookalikes, such as Euonymus ‘Jean Hugues’, Ilex crenata and Phillyrea latifolia, which can be clipped into formal shapes, if that is your thing.

Less clippable, but with a neat flowering habit, are the smaller hebes, while warm, sunny gardens can benefit from an array of Mediterranean flowering evergreens, ever-greys and shrubby euphorbias.

IN LARGER GARDENS

Stalwarts such as evergreen viburnums, choisyas and olearias all earn their keep in a flowery informal garden and as punctuation mark plants in a mixed border, and most are unfussy about full sun (although they grow more compact and flower better the more sun they get).

In gardens with neutral to acid soil, slow-growing camellias and rhododendrons are an obvious choice. Any of the above, when planted together with taller, relatively fast-growing evergreens with less significant flowers but with interesting shaped or coloured leaves (e.g. photinia, Corokia ‘Bronze King’, the pittosporums, eleagnus and variegated rhamnus) will make an informal hedge to mask a 2m-high fence in two or three years after planting (researching average rates of growth for each is essential when deciding how to space them). It is worth noting that evergreens that have New Zealand origins tend to be wind-tolerant, which can be an added bonus.

A WORD ON SCREENING

First came towering shiny laurel, then came more textured conifers (and the infamous Cupressus x leylandii). Then there was a fad for glaucous eucalyptus. Hot on the heels of this came the great bamboo invasion. All are offered up as the answer to the “how do I hide my neighbour’s satellite dish/loft extension” question.

An evergreen described as “fast growing” inevitably means the words “high maintenance” should also be on the label. Furthermore, one household’s “screen” can be the next-door neighbour’s area of uncultivatable shade and, in “hiding” whatever-it-is, the evergreen might do just the opposite, namely draw attention to it by its very overbearing presence.

In all cases, using the light canopy of a garden-friendly deciduous tree such as a winter flowering cherry, a fruit tree or a white-stemmed birch to literally draw a veil over the perceived eyesore would be preferable. There are many column inches written here and elsewhere about small garden trees, but I thought it would be useful to mention them again, for their many benefits.

Even a small garden benefits from a few evergreens to lend year-round structure, in this case a group of clipped box balls