She-Oak Casuarina equisetifolia

Coastal she-oak is a fast growing tree of foredunes and headlands, developing an open, spreading crown on a straight trunk. What look like drooping grey green needles are jointed branchlets, the true leaves reduced to tiny scales at each joint, and the whole canopy sighs in wind. It is one of the few large trees that will grow directly in exposed coastal sand under salt wind, which is why it is used for foredune windbreaks, shelterbelts, beachfront shade and large scale coastal revegetation.

Salt, sand and open ground

Full sun and a warm climate. Its natural range runs along the tropical and subtropical coast, so it suits Queensland, northern New South Wales and the far north of Western Australia, and it is not a tree for cold frosty inland districts or for southern coastlines. Soil is barely a constraint: it grows in pure sand, tolerates salt spray and saline groundwater, and fixes its own nitrogen through root associations, so it establishes on ground with almost nothing in it. Water through the first year, then leave it alone. For a windbreak, plant in a staggered double row set well back from the boundary. On a beachfront site, plant small stock rather than advanced trees, because young plants anchor themselves against wind far better than a large transplant does.

The failure mode is putting it near a building. This is a large tree with a substantial root system, it drops a continuous litter of shed branchlets that blocks pool filters and gutters, and that litter mats down and suppresses grass and most understorey beneath it. It is a good tree in the right paddock and a constant nuisance over a courtyard, a pool surround or a narrow verge.

Coastal she-oak or swamp she-oak

The two casuarinas in this range suit different ground. Swamp she-oak is the eastern species for waterlogged clay, brackish flats and saline sites, and it throws root suckers freely, which makes it a shelterbelt and revegetation tree rather than a garden one. Coastal she-oak is the sand and salt wind specialist, warmer in its climate range and better on a dune or beachfront reserve, and it does not sucker the way glauca does. Pick coastal she-oak for exposed sandy coast in warm districts, swamp she-oak for wet or salty ground further south. Neither belongs in a suburban back garden, since both are shelter and revegetation trees at heart. Both sit in the screening range.

Early shaping and litter management

Pruning is limited to structure and it is done early. Remove double leaders and any low branches you want gone in the first few years, in late winter, then leave the crown to develop, since large cuts into mature wood are slow to seal. It needs no feeding on most sites, because the nitrogen fixing root nodules do that work, and a native fertiliser in the first spring is enough on very poor sand. Rake shed branchlets off paths and pool areas, and use them as mulch under the tree where little else will grow anyway.

Choosing a size

This plant is supplied in one size, 90L, at $479.00 per plant. The size shown is the pot it arrives in, which is the rootball, not the height of the plant. Not sure which to choose? Read our guide to fast growing screening plants.