Italian Alder Alnus cordata

Italian alder holds a narrow, upright, conical frame and suits avenues and boundary lines where a broad crown would be in the way. The leaves are the giveaway: heart shaped, glossy and dark, held late into autumn on a deciduous tree, with yellow catkins hanging in late winter and small woody cone like fruit persisting afterwards. It is planted as a screening and windbreak tree, and on poor or disturbed ground it does extra work, because it fixes nitrogen through root nodules and improves the site as it goes.

Cool district planting for Italian alder

Alnus cordata is a southern European tree and it earns its place in cooler Australian districts: the tablelands, central and western Victoria, the Adelaide Hills, Canberra and southern New South Wales, where the winter chill gives it a proper dormancy. Full sun, and it is not fussy about soil. Compacted clay, gravelly fill, alkaline ground and reclaimed sites all suit it, which is why it turns up on subdivision and rehabilitation plantings where other trees give up. Coastal wind does not bother it either. Space a windbreak or screening row generously, and stagger two lines if you want wind broken properly rather than funnelled between trunks. The one thing that goes wrong is siting. People buy it for the narrow young shape and put it close to a house, a fence or a service trench, then find the crown broadens as the tree matures and the trunk keeps thickening. This is a full size forest tree, not a columnar cultivar, so give it open ground and plan around the mature spread from the day you dig the hole.

Italian alder next to tipu and michelia

The other deciduous tree in this batch is Tipuana tipu, and the two barely overlap. Tipu is a warm climate tree with a broad flat top and roots that lift paving; the alder is upright, cold tolerant and far better behaved along a boundary. If your winters are genuinely cold and you want height without width, the alder is the pick. Where the requirement is a year round screen rather than a line of trunks, look at Michelia Fairy White instead, because the alder stands bare for part of winter and the privacy goes with the leaves. Plenty of properties use both: alders for the outer windbreak, evergreens for the sight line.

Dormant season pruning and going easy on nitrogen

Prune in late winter while the tree is dormant and before the buds move. Formative work matters more than anything done later: settle on one leader, remove competing verticals, and lift the lower branches over a few seasons rather than all at once. Mature alders need little beyond dead or crossing wood. Feeding is where people overdo it. The tree fixes its own nitrogen, so a high nitrogen fertiliser only pushes soft growth that catches the wind. A mulch ring and a light application of a complete fertiliser in early spring on genuinely poor ground is enough. Browse the rest of the range in advanced trees.

Choosing a size

This plant is supplied in one size, 45L, at $229.00 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 when to plant in Australia.