Coastal Rosemary Westringia fruticosa Jervis Gem

Jervis Gem is a compact selection of coastal rosemary, denser and lower than the taller forms, with narrow grey-green leaves in whorls of four along stiff stems. The flowers are mauve rather than white, appearing on and off through the year with a heavier flush in spring, and that colour is the main reason to choose it over its siblings. It goes into low clipped hedges, kerbside and median mass planting, path edging, and front line coastal gardens where wind pruning does half the work.

Full sun or nothing, and the shade that thins it out

Give it an open position with free draining soil and it needs almost nothing: salt wind, sand, reflected heat off paving and long dry spells are all within its tolerance, and once established it can be left to rainfall in most coastal gardens. Set plants around 40 to 50 cm apart for a low hedge so the row closes quickly and can be shaped as one. The failure that catches people out is shade. Planted on the shaded side of a house, under a tree canopy or behind a fence that blocks the sun for half the day, Jervis Gem stretches for light, thins out, flowers poorly and goes hollow at the base, and no amount of clipping brings it back, because it will not reshoot from the bare wood you would have to cut into. Site it in sun from the start. Wet heavy soil is the other thing to avoid, so mound the row on clay rather than digging individual holes that hold water. Frost is handled in most temperate districts, and the plant accepts clipping from a young age, which lets a row of small stock be shaped in its first year.

Mauve flowers, white flowers, or the full sized species

Within the westringias here the differences come down to flower colour, leaf size and final height. Zena carries white flowers with faint throat markings on a finer leaf and takes a tighter clipped face, so it is the more formal option. The straight species, Westringia fruticosa, is taller and more open, suited to informal hedges, batters and large scale mass planting where bulk matters more than neatness. Take Jervis Gem when you want mauve flower against grey foliage and a low hedge that keeps its shape without constant attention. The flower colour also changes what you can plant beside it: mauve sits comfortably with silver foliage and blue flowered natives, where the white forms hold a cleaner line against rendered walls and dark green hedging. All three sit in the hedging range.

Trimming after each flush, and a light feed

Keep the shears moving. A light trim after each flowering flush holds the plant tight from the base and brings on the next round of flower, while plants left alone for a few years open in the middle and are hard to bring back. Always leave leafy growth below the cut. Feed lightly if at all, since a small spring application of general fertiliser is enough and rich feeding produces soft growth that burns in salt wind and flops after rain. Water through the first summer, then taper off, paying attention to any part of the row sitting above a hot kerb where the soil dries fastest.

Choosing a size

This plant is available in 6 sizes, from 125mm up to 300mm, priced from $16.95 to $93.95 per plant. The size shown is the pot the plant arrives in, which is the rootball, not the height of the plant. These are younger plants, priced for planting in quantity, and they establish quickly once in the ground. Not sure which to choose? Read our guide to coastal planting.