Coastal Rosemary, scientifically known as Westringia fruticosa, belongs to the Lamiaceae family, commonly referred to as the mint family, which includes aromatic plants like rosemary and lavender. It is part of the genus Westringia, comprising about 30 species native to Australia. The species name fruticosa comes from Latin, meaning “shrubby” or “bushy,” reflecting its growth habit.
The genus is named after Johan Peter Westring, an 18th-century Swedish physician and botanist. Westringia fruticosa is closely related to Prostanthera (Australian mint bushes) but is distinguished by its whorled leaves and five-lobed calyx, as opposed to the two-lobed calyx of Prostanthera.
Westringia fruticosa is an evergreen shrub, typically growing 4–6 feet tall and 5–8 feet wide, though some cultivars are more compact or prostrate. Its small, linear to lance-shaped leaves, about 0.5–1 inch long, are gray-green above with a velvety white underside, arranged in whorls of 3–5 around whitish stems, resembling culinary rosemary.
The plant produces small, white to pale lavender flowers with orange-to-purple spotted throats, blooming profusely in spring and intermittently year-round in mild climates. Flowers are labiate, typical of the mint family, and borne in leaf axils. The shrub forms a dense, rounded mound, with cultivars like ‘Mundi’ (1–2 feet tall) or ‘Blue Gem’ (bluish-purple flowers) offering varied aesthetics.
Coastal Rosemary is native to eastern Australia, primarily along the coast of New South Wales from Forster to Eden, with some records in Queensland and Victoria. It naturally occurs on coastal cliffs, sand dunes, and hills, thriving in sandy, alkaline, or shale-enriched soils. The plant is a key component of coastal shrublands, heathlands, and dune forests, enduring strong winds, salt spray, and poor soils.
Due to its ornamental value, it has been widely cultivated and naturalized in other parts of Australia, North America, and Europe, particularly in Mediterranean-climate regions like California, where it is popular in waterwise landscapes.
Westringia fruticosa is hardy in USDA Zones 9–11, tolerating temperatures down to about 15–20°F (-9 to -7°C) for short periods. It thrives in warm, frost-free climates with mild winters, making it ideal for coastal areas of California, Florida, and the southeastern U.S. In colder regions (Zone 8), it may survive with protection or in pots moved indoors during freezes. The plant prefers full sun but tolerates partial shade, especially in hotter inland areas, and is highly adaptable to drought and coastal conditions once established.
Coastal Rosemary is primarily an ornamental shrub, valued for its fine-textured foliage, year-round blooms, and resilience in tough conditions. It is widely used in waterwise, coastal, and Mediterranean gardens as a ground cover, low hedge, or specimen plant, with cultivars like ‘Mundi’ excelling as prostrate ground covers and ‘Naringa’ as taller hedges.
Its salt and wind tolerance make it ideal for seaside landscapes, while its drought tolerance suits xeriscaping. The flowers attract bees, butterflies, and small birds, supporting biodiversity. Though not edible like true rosemary, it is low-maintenance, deer-resistant, and virtually pest-free, making it a favorite for parks, streetscapes, and erosion control on slopes. In traditional settings, it has minor medicinal uses, but its primary role is aesthetic and ecological.
Cultivation of Coastal Rosemary (Westringia fruticosa)
Select a Suitable Location
Choose a site with full sun for optimal growth and flowering, though Coastal Rosemary tolerates partial shade, especially in hotter inland areas. Ensure the location accommodates the plant’s mature size, typically 4–6 feet tall and 5–8 feet wide for the species, or smaller for cultivars like ‘Mundi’ (1–2 feet tall). The site should have good air circulation and be protected from prolonged freezes in marginal zones.
Ensure Well-Drained Soil
Plant in well-drained soil, as Coastal Rosemary thrives in sandy, loamy, or rocky soils with a pH of 6.0–8.0, tolerating alkaline conditions common in coastal areas. It struggles in heavy clay or waterlogged soils, which can cause root rot. Test soil drainage and amend with sand, grit, or compost to improve structure if needed, particularly in dense soils.
Plant in the Right Season
Plant in spring or early fall to allow roots to establish before extreme heat or cold. Dig a hole twice as wide and as deep as the root ball, positioning the crown at ground level. Backfill with native soil mixed with compost for nutrient-poor sites, water thoroughly, and apply a 2–3-inch layer of mulch (e.g., gravel or bark) to retain moisture, keeping it away from the stem.
Water Sparingly After Establishment
Water deeply but infrequently during the first year, providing 1 inch of water weekly to encourage deep roots. Once established (1–2 years), Coastal Rosemary is highly drought-tolerant and typically relies on rainfall in suitable climates. Supplemental watering every 2–3 weeks during prolonged dry spells enhances vigor, but avoid overwatering to prevent root issues.
Mulch for Soil Health
Apply a 2–3-inch layer of organic or inorganic mulch, such as gravel, wood chips, or crushed stone, around the base, extending to the drip line but avoiding contact with the stem. Mulch conserves moisture, regulates soil temperature, and reduces weed competition, which is especially beneficial in coastal or arid conditions where soil dries quickly.
Fertilize Lightly
Coastal Rosemary requires minimal fertilization due to its adaptation to nutrient-poor soils. In spring, apply a low-nitrogen, slow-release fertilizer (e.g., 5-10-10) or a light layer of compost to boost growth, particularly in sandy soils. Avoid high-nitrogen fertilizers, which promote leggy growth and reduce flowering. A soil test can guide nutrient applications.
Prune for Shape and Density
Prune lightly in late winter or early spring to maintain shape, remove dead or damaged growth, and encourage bushiness. For hedges, shear regularly to promote dense foliage, but avoid cutting into old wood, as the plant may not resprout vigorously. Tip-pruning after flowering maintains compact forms like ‘Mundi’ or ‘Smokey’. Always use clean, sharp tools to prevent disease.
Monitor for Pests
Coastal Rosemary is virtually pest-free but may occasionally attract spider mites or scale in hot, dry conditions. Check for webbing, stippling, or sticky residue on leaves. Treat minor infestations with a strong water spray or insecticidal soap, and ensure good air circulation to prevent issues. Encourage natural predators like lacewings to maintain pest control.
Prevent Diseases
The plant is highly disease-resistant, but root rot (e.g., from Phytophthora) can occur in poorly drained soils. Ensure proper drainage and avoid overwatering to prevent fungal issues. If leaves yellow or wilt, check for soggy soil and improve drainage. Remove affected roots or plants promptly and avoid replanting in the same spot without soil remediation.
Protect from Cold Damage
In Zones 9–11, Coastal Rosemary is frost-tolerant, but in Zone 8 or during unexpected freezes, protect young plants with frost cloth or mulch around the base. Plant in sheltered sites, such as near walls, to minimize cold exposure. In colder regions, grow in pots and move indoors during winter, maintaining temperatures above 15°F (-9°C).
Support Pollinators
The plant’s white to lavender flowers attract bees, butterflies, and small birds, especially during spring blooms. Avoid pesticides during flowering to protect pollinators. Pair with nectar-rich plants like salvia or lavender to create a pollinator-friendly garden, enhancing biodiversity in coastal or xeriscape settings.
Propagate for Expansion
Propagate Coastal Rosemary via semi-hardwood cuttings in summer or seed, though cuttings are preferred for cultivars to ensure true-to-type plants. Take 4–6-inch cuttings, dip in rooting hormone, and plant in a mix of sand and peat, keeping moist until rooted (6–8 weeks). Seeds require scarification and may not produce uniform plants, making them less common for propagation.
Choose Appropriate Cultivars
Select cultivars based on your garden’s needs and climate. ‘Mundi’ is a low, prostrate form (1–2 feet) for ground cover, while ‘Naringa’ grows taller (6–7 feet) for hedging. ‘Blue Gem’ offers bluish-purple flowers, and ‘Smokey’ features variegated gray-white foliage. Ensure the cultivar’s size and hardiness suit your USDA Zone and aesthetic goals.
Additional Tips
- Long-Term Care: With a lifespan of 10–15 years, regular pruning and soil care maintain vigor. Pair with succulents or native grasses for a cohesive, low-water landscape.
- Staking: Rarely needed, but stake young plants in windy coastal areas for the first year to stabilize roots, removing stakes after establishment.
- Coastal Adaptation: Its salt tolerance makes it ideal for seaside gardens; plant in exposed sites to leverage its wind resistance.