Broom
Carmichaelia appressa
A low, appressed broom adapted to exposed, sunny, stony habitats. Leafless, flattened green stems perform photosynthesis and resist drought and wind. Provide sharp drainage and full sun. shrubs .
Plant Description
Botanical Features
Carmichaelia appressa (Native Broom) is a unique, prostrate shrub that forms dense, flattened mats of stiff, interlacing green stems (cladodes). It essentially lacks true leaves, using its green stems for photosynthesis-an adaptation to dry environments. In summer (October-January), the mat is covered in small, pea-like flowers that are white with purple veins, followed by small seed pods.
Quick Facts
Content for Carmichaelia appressa ( Carmichaelia appressa ).
| Scientific Name | Carmichaelia appressa |
|---|---|
| Height | 0.3-2 m (compact shrub) |
| Spread | 40-120 cm across |
| Water Needs | Low to moderate; free-draining soils |
| Light | Full sun |
| Frost Tolerance | High - tolerant of severe freezes |
| Salt Tolerance | Low to moderate |
| Growth Rate | Slow to moderate |
| Lifespan | Long-lived perennial |
Climate Suitability
Content for Carmichaelia appressa ( Carmichaelia appressa ).
| City | Climate Suitability |
|---|---|
| Whangārei | Suitable |
| Auckland | Suitable |
| Hamilton | Suitable |
| Tauranga | Suitable |
| Rotorua | Suitable |
| Gisborne | Suitable |
| New Plymouth | Suitable |
| Napier | Suitable |
| Whanganui | Suitable |
| Palmerston North | Suitable |
| Wellington | Suitable |
| Nelson | Suitable |
| Christchurch | Suitable |
| Dunedin | Suitable |
| Invercargill | Suitable |
Natural Habitat
Kaitorete Spit Endemic
This species is strictly endemic to the Kaitorete Spit in Canterbury, New Zealand. It is a specialist of stable sand dunes, gravelly ridges, and shingle lag plains. It grows in extremely free-draining, low-nutrient substrates and is exposed to constant salt-laden winds and high solar radiation.
Conservation Status
Current Threats and Protection
Listed At Risk (Localised). Key pressures include browsing, habitat loss and weed invasion. Site protection and pest control support persistence.
How to Grow
Cultivation Requirements
Provide maximum sun, sharp drainage and low fertility. Avoid overhead irrigation in winter. Prune lightly after flowering to maintain low, tidy habit.
Planting Guide
Cultivation
This broom requires full sun and extremely free-draining soil. It thrives in sandy, gravelly, or rocky sites where other plants would desiccate. It is very drought-tolerant once established. Avoid rich, heavy, or wet soils, which will cause root rot and rapid death. It is perfectly suited for a gravel garden, scree bed, or coastal rockery.
Ecological Role
Nitrogen Fixer
Like all legumes, it fixes atmospheric nitrogen through root nodules, allowing it to colonize and thrive in nutrient-poor gravels. Its dense, mat-forming habit helps stabilize the loose substrate of its habitat, reducing wind erosion. The flowers provide a food source for native bees and butterflies in an otherwise sparse environment.
Uses
Landscape Value
Valued for its toughness and ground-covering ability in dry, exposed sites. It forms a "living mulch" that suppresses weeds and retains cool root runs for other plants. It is an excellent subject for native xeriscaping (low-water gardening) and coastal restoration projects within its range.
Landscaping Uses
Garden Design Applications
Excellent for rock gardens, alpine collections, and naturalistic plantings. Best used in open, well-drained positions where its distinctive form can be appreciated. Combines well with other native alpine plants and provides year-round structure. Consider placement carefully due to sharp foliage - avoid high-traffic areas. Creates dramatic focal points in contemporary and native-themed garden designs.
Seasonal Care
Year-Round Maintenance
Spring management focuses on removing winter-damaged foliage and assessing drainage. Summer care emphasizes maintaining adequate moisture without waterlogging. Autumn preparation includes reducing irrigation and ensuring good air circulation. Winter protection may require covering in areas subject to excessive moisture. Year-round monitoring ensures early detection of problems and maintenance of optimal growing conditions.
Pruning
Maintenance
No pruning is generally required. The plant naturally maintains a low, prostrate habit. Any dead stems can be snipped out if necessary. If it encroaches on paths, it can be trimmed back, but it is slow-growing enough that this is rarely an issue.
How to Grow Broom
From Seed
Carmichaelia appressa is easily propagated from seed. The seeds have a hard coat and benefit from scarification (nicking the seed coat with a knife or sandpaper) or soaking in hot water (pour boiling water over seeds and let stand for 12-24 hours) before sowing to improve germination. Sow pre-treated seeds in spring onto a free-draining seed-raising mix, lightly covering them. Maintain consistent moisture but avoid waterlogging. Germination can be variable but usually occurs within a few weeks to months after proper pre-treatment. Once seedlings are robust enough, prick them out into individual pots and grow them on in a sunny, well-ventilated location until ready for planting out.
From Cuttings
Semi-hardwood cuttings can also be taken in summer, though seed is generally considered more reliable for this species. Select healthy, firm stem sections (cladodes) about 8-10 cm long. Remove any soft growth from the tip and base, and treat the cut end with a rooting hormone. Insert the cuttings into a very free-draining mix of sand and perlite. Place in a sheltered, well-ventilated environment with good humidity but avoid excessive moisture around the stems to prevent rot. Rooting typically occurs within a few months, but can be slower.
General Cultivation
Carmichaelia appressa is a unique, prostrate broom that thrives in exposed, sunny, stony habitats, making it an excellent choice for rock gardens, gravel gardens, and coastal areas. It requires maximum sun exposure and exceptionally sharp drainage, performing best in lean, mineral soils with high grit content (e.g., 50-70% gravel or coarse sand). Avoid rich composts, heavy clays, or waterlogged conditions, which will quickly lead to root rot and plant demise. Once established, it is very drought-tolerant and requires minimal watering. Avoid overhead irrigation, especially in winter, to keep the crowns dry and prevent fungal issues. This species is hardy to severe freezes. Minimal pruning is typically required; light trimming after flowering can help maintain its low, tidy habit and encourage denser growth. Its prostrate, mat-forming habit effectively stabilizes loose substrates and acts as a living mulch.
Pests and Diseases
Common Issues
Caterpillars (such as the Kōwhai Moth caterpillar) and slugs can sometimes graze on the stems or flowers. In garden settings, it may be susceptible to root rot fungi (Phytophthora) if overwatered or grown in heavy clay. Keeping the crown dry and ensuring sharp drainage is the best prevention.
Cultural Significance
Conservation Icon
As a single-location endemic, Carmichaelia appressa is a conservation icon for the unique biodiversity of the Kaitorete Spit ecosystem. Its survival is linked to the protection of this rare gravel-barrier landform.
Bonus Tip
Leaf Adaptation
The lack of leaves is a brilliant evolutionary strategy. By photosynthesizing through tough, green stems (cladodes), the plant minimizes water loss through transpiration, allowing it to survive in its arid, windswept home.
