Conifers for screening and structure: what to plant and what to avoid

Conifers usually enter the conversation with a fence line in mind: a second storey has gone up next door, and a row of something evergreen and upright looks like the fix. Conifers do it well and hold a formal shape. But the group runs from columns that stop at three metres to forest trees the height of a power line, and the difference does not show for six years, by which point you are paying an arborist. This guide sorts the conifer range by job.

Work backwards from the finished height

Decide the height the screen must hold, then buy a plant that reaches roughly that height on its own. A conifer held well below its natural size needs clipping two or three times a year forever, and clipping is where conifers go wrong. If you need eight metres, accept you are planting a tree and give it a tree's worth of room.

Separate the two jobs. Screening is a green wall in a line, judged on how fast it closes and how well it holds foliage low. Structure is a single plant used as a shape: a dark vertical at a path's end, or a matched pair at a gate. Most disappointing plantings ask one to do the other's job.

Italian cypress for formal verticals

Cupressus sempervirens sits behind most formal verticals in Australian gardens, and it works because the narrow column is genetic rather than maintained. Italian Cypress Stricta is the standard tight green column, Cupressus sempervirens Glauca carries a blue-grey cast that suits rendered walls, and Nitschkes Needles is a narrow selection with fine foliage for shallow beds.

Italian cypress wants full sun and free drainage, and rots in a wet lawn corner or clay that stays damp through winter. Young columns splay open after heavy rain or wind, so tie the upper third softly for the first few years. Used as a screen, a row at one metre centres makes a narrow wall at head height and above, though the base thins where the row is crowded or shaded, so plan a low hedge in front if you need cover low down.

Fast screening, and the honest problem with Leyland cypress

Leyland cypress is the quick option in the privacy screening range and a common regret. Leighton Green is the standard dark green form, Castlewellan Gold the gold-toned one, slightly less vigorous but the same in temperament. Both can put on a metre a year and close a boundary in three or four seasons.

Here is what that speed costs. Left alone, a Leyland cypress is a forest scale tree well over twenty metres, and it does not stop at the height that suited you. Holding one at three or four metres means clipping twice a year for as long as you own the house. Miss two seasons and you cannot bring it back, because a conifer cut into bare wood does not regrow. Add a hungry surface root system and a high susceptibility to cypress canker, and the sums change.

Buy it only with real depth on the boundary and a commitment to clipping twice a year. Otherwise use a plant that stops on its own. Juniperus chinensis Spartan is a dense dark green column that holds its shape and handles heat and dry once established. Thuja occidentalis Smaragd gives a soft narrow cone for temperate gardens, and Cupressus torulosa Arctic Green suits a clipped hedge inland. Our guide on how many plants you need for a hedge covers counting.

Native conifers: Callitris and Podocarpus

Australia has its own conifers and they are under-used. The cypress pines, Callitris, are fine textured, drought hardy once established, and better suited to hot dry inland gardens than anything from a northern mountain. Port Jackson Pine makes a neat conical tree on the eastern seaboard, Callitris preissii is the Rottnest Island form for coastal salt and wind, and Callitris gracilis the slender one. All want drainage and to be left alone: they resent wet feet and root disturbance, and will not take hard pruning. Water through two summers, then stop. They belong on any shortlist from the native range.

Illawarra Plum is the useful outlier: a conifer botanically that reads as a broad-leaved evergreen, dark, glossy and dense, and the one plant here that forgives a hard cut and reshoots from older wood. That makes it the safer choice for a formal clipped hedge, and it handles humidity and coastal air far better than the cypresses. It fruits, and the soft plums stain paving, so keep a clipped run off a pale path.

Araucaria as a landmark tree

The araucarias are not screening plants but single specimens with an architectural silhouette, and they need acreage or a large front garden. Bunya Pine and Hoop Pine are Queensland natives that mature into very large trees. Norfolk Island Pine is the coastal one, salt and wind tolerant. One warning on Bunya: mature trees drop cones weighing several kilograms, so never plant one over a driveway, path or play space. Buy at size from the feature trees or advanced trees range: the shape is the point and takes years.

Spacing a conifer screen

Spacing is where good plants get ruined: crowded conifers shade each other's inner faces and those faces never recover.

For Leyland cypress held at three to five metres, plant 1.5 to 2 metres apart. For narrow columns such as Spartan juniper or Thuja Smaragd, 800mm to one metre. For Italian cypress used as a screen, one to 1.2 metres. For a Podocarpus hedge, 750mm to one metre. Use a single row rather than a staggered double, and keep the line a metre back from the fence for anything Leyland sized so you can get behind it to clip.

Conifers do not reshoot from brown wood

This is the rule that makes or breaks a conifer planting. Cupressus, Leyland cypress, Callitris, Thuja and juniper carry almost no dormant buds in old bare wood. Cut into the brown interior and you get a bare patch that stays bare for the life of the plant; no feeding or watering fixes it. The araucarias behave the same way about a lost leader: top one and the shape never returns.

So the pruning rule is narrow. Clip only into green growth, lightly and often, and start while the plant is short of the target height so you build a dense outer skin. Never top a conifer expecting it to thicken, and never buy one assuming you can cut it back later. Podocarpus will take a hard renovation. The rest will not.

Canker and root rot

Two problems account for most conifer failures. Cypress canker turns individual branches or whole limbs bronze while the rest of the plant looks healthy, often with sunken lesions and resin bleeding. It is not only a coastal problem: Monterey and Leyland cypress have been hit hard through Victoria, South Australia and inland NSW, where drought stress makes it worse. No spray cures it. Cut affected limbs well below the damage, disinfect tools between cuts, and remove badly affected plants. Every cut is a way in, so prune in dry weather and keep wounds small by clipping the outer green on time rather than taking limbs off later.

Root rot is a drainage problem, not something the plant catches. Heavy clay, an irrigation line against the trunk, or mulch piled up the stem will do it. Plant on a raised mound in clay and keep mulch and drippers clear of the trunk.

When not to buy a conifer

Skip conifers if your boundary strip is under about 1.2 metres and you still need to reach the fence: clipping both faces is miserable and the shaded face browns out anyway. Our notes on screening plants for narrow spaces cover better options. Skip them in wet ground and irrigated lawn, and in deep shade, where they thin and never fill in. On the humid subtropical coast the cypresses are usually short lived, with canker and root rot both common, and cool climate species such as spruce and western red cedar are a poor bet. Use Podocarpus, Araucaria or Callitris. And if you want a plant you can reshape later, or one that flowers and feeds birds, choose from the low maintenance range.

What size to buy

For a long screen, 200mm to 400mm pots are the sensible buy: smaller conifers establish quickly, catch a larger plant within a few seasons, and the saving across twenty is real. Keep large stock for structure roles, where a matched pair at a gate must look deliberate from day one. Water through the first two summers and keep mulch off the trunk. None of these are heavy feeders, and Callitris does better lean than fed.

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