Giant Silver Plum Bromeliad Alcantarea imperialis Silver Plum

Silver on top, plum underneath: that two tone leaf is what sets this giant bromeliad apart. The leaves are broad and strap shaped, and as they arch out from the centre the dark undersides show along their length, so from across a garden the plant reads as pewter and wine rather than plain green. It builds a single, symmetrical vase, typically 1 to 1.5m across in gardens when mature, which makes it a sculptural plant for open ground or a large pot rather than one for a shady corner.

The leaf edges are smooth, with none of the hooked teeth that make many bromeliads painful to handle, so it can sit beside steps, a pool or a busy path. It is also slow, filling out over several years rather than a season, and each rosette flowers just once, a long way down the track.

Full sun for the strongest silver and plum

Colour follows light. In full sun the silver is brightest and the plum underside darkest, and the rosette stays tight and upright; in part shade it drifts greener, and in real shade the leaves lengthen, soften and flop. A plant grown on under shade cloth needs a few weeks of gradual exposure before it faces a summer afternoon, or the leaves bleach and scorch. Once settled it takes heat, wind and dry spells well, which suits it to open, frost free gardens along the coast from Sydney into Queensland. In south eastern Brazil it grows on granite outcrops, and that decides the planting: drainage first. Plant it high in gritty, free draining soil, at the depth it sat in its pot, or in a large, heavy pot of coarse mix that will not tip once the cups are full of water. Frost is the limit. A light one marks the leaves and repeated frosts can kill the centre, so in cooler districts give it a sheltered spot under a pergola or a deep eave, or keep it in a pot you can shift before winter.

One flower, after a long wait

Flowering usually takes many years. When it comes, a tall, branched spike rises well clear of the leaves and carries pale cream flowers among its bracts. After that the parent rosette slowly dies back over a year or more. It may leave a few offsets at its base, but this species is not generous with them, so do not plan on a clump of replacements. That is the real drawback of a giant bromeliad bought as a centrepiece: you cannot choose when the change comes, and whatever follows takes years to reach the same size. Cut the spent spike low once it dries, peel dead outer leaves off cleanly, and leave any offsets attached until they are a good size before cutting them free with a sharp knife.

Water in the cups, and how it compares

Rain caught in the leaf bases is how it drinks, so in a long dry spell water over the top of the rosette as well as the soil. That standing water can breed mosquitoes, so tip or flush the cups with fresh water every week in warm weather, and in the dengue mosquito country of north Queensland, do it without fail. Feed lightly: a pinch of slow release fertiliser on the soil in spring and nothing in the cups, because rich feeding greens the leaf and dulls the silver. Keep copper well away, since copper fungicides and copper based fertilisers both damage bromeliads. Against the green Alcantarea imperialis, Silver Plum gives the same scale in a paler, cooler colour; the Rubra form trades the silver for burgundy, and Alcantarea extensa is the one for a smaller pot. The silver ties in with grey foliage such as westringia or olive, and the plum picks up dark leaved cordylines. For other plants that cope once settled, browse Low Maintenance Plants or read Low water gardens.

Choosing a size

This plant is supplied in one size, 400mm, at $449.00 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 low water gardens.