Lophomyrtus obcordata (Rohutu): Complete Shrub Growing Guide
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Lophomyrtus obcordata
1. Introduction & Taxonomy
Lophomyrtus obcordata, the rohutu or New Zealand myrtle, is a charming small-leaved shrub endemic to New Zealand. This member of the myrtle family features distinctive heart-shaped leaves, aromatic foliage, and tiny white flowers followed by colorful berries. Its compact habit and ornamental appeal make it increasingly popular in native gardens and containers. Lophomyrtus obcordata is notable for its white flowers.
A shrub or small tree with mottled bark, tiny, rounded, reddish leaves and sprays of small, white flowers followed by small, purplish to black fruits. Lophomyrtus obcordata is native to forests throughout New Zealand. It adapts readily to cultivation in a range of temperate climates. The seeds require cold stratification around 4°C for at least 4 weeks after sowing.
Taxonomic Classification
Habitat and Distribution
Lophomyrtus obcordata is native to forests throughout New Zealand. This species inhabits environments typical of the Myrtaceae.
Botanical Note: A family of aromatic, evergreen trees and shrubs concentrated in Australia and tropical America. Many have essential oils and edible fruits. Includes eucalyptus, guava, and bottlebrush.
Native Range & Distribution Map
The map below shows the native range and notable cultivation regions for Lophomyrtus obcordata.
2. Biology & Morphology
Growth Form & Architecture
Lophomyrtus obcordata is a multi-stemmed woody plant, typically smaller than a tree, with several stems arising from or near the base.
Flowers & Reproductive Structures
Shrub flowers vary enormously across families, from tiny wind-pollinated catkins to large, showy insect-pollinated blooms. The flowers are white in colour.
Key Characteristics
- Height: 1-3m
- Growth Habit: Erect Shrub
- Growth Rate: Moderate under optimal conditions
- Life Cycle: Perennial
3. Reproduction & Propagation
Primary propagation methods for Lophomyrtus obcordata: Cuttings, seed, or layering (varies by species).
Propagation Methods
Propagated by semi-hardwood cuttings in summer, softwood cuttings in spring, or seed. Division may work for suckering species.
Propagation Tip: Use rooting hormone and maintain high humidity for best cutting success.
4. Cultivation Requirements
Soil / Substrate
Well-draining, moderately fertile soil. A mix of garden loam, compost, and coarse sand.
Watering
Regular watering during the growing season. Allow soil surface to dry slightly between waterings.
Light Requirements
Full sun to partial shade. Most ornamental shrubs perform best with at least 4-6 hours of direct light daily.
Temperature
- Optimal Growth: 18-30°C (65-86°F)
- Minimum Tolerance: -12°C (10°F)
- USDA Hardiness: Zones 8-11
Pruning
Prune after flowering to maintain shape. Remove dead, damaged, or crossing branches.
Fertilization
Apply a balanced slow-release fertilizer in spring. Most shrubs are moderate feeders.
Common Cultivation Mistake: Over-watering is the most common cause of shrub failure. Ensure good drainage and match watering to the species' natural habitat.
Seasonal Care Calendar
Follow this season-by-season guide for optimal care timing throughout the year.
🌱 Spring (March–May)
Active growth begins; apply native plant fertilizer low in phosphorus. Good time for planting and propagation from cuttings. Flowering begins late spring.
☀️ Summer (June–August)
Peak flowering through summer; maintain moisture during hot weather. Monitor for myrtle rust on new growth. Light pruning to shape after main flowering flush.
🍂 Fall (September–November)
Berries ripen through autumn in attractive progression of colors. Reduce watering as temperatures cool. Good time for planting in mild climates. Collect seeds from ripe berries.
❄️ Winter (December–February)
Minimal care required; hardy throughout New Zealand. Can prune for shaping if needed. Avoid fertilizing during dormancy. Tolerates light frost to -8°C once established.
5. Diseases & Pests
Lophomyrtus obcordata is generally robust and pest-resistant when cultural conditions are optimal.
Major Diseases
Root Rot (Phytophthora, Pythium)
Caused by overwatering or poor drainage. Ensure good drainage and avoid waterlogging. Improve soil aeration.
Powdery Mildew
White powdery coating on leaves. Improve air circulation, avoid overhead watering, and apply fungicide if severe.
Leaf Spot (various fungi)
Brown or black spots on foliage. Remove affected leaves, improve airflow, and avoid wetting foliage.
Common Pests
- Scale Insects — Hard or soft scales on stems and leaves; treat with horticultural oil
- Spider Mites — Fine webbing on undersides of leaves in dry conditions; increase humidity
- Mealybugs — White cottony masses at leaf axils; spray with soapy water or neem oil
- Aphids — Cluster on new growth; spray with soapy water or introduce ladybirds
- Whiteflies — Tiny white insects on leaf undersides; use yellow sticky traps
IPM: (1) Choose the right species for your conditions. (2) Maintain good air circulation and hygiene. (3) Monitor regularly and act early. (4) Use chemical controls only as a last resort.
6. Indoor & Container Growing
Lophomyrtus obcordata can be grown in containers and brought indoors during winter in cold climates.
Container Selection
Use containers with adequate drainage holes. Choose pots at least 5 cm larger than the root ball. Plastic retains moisture longer; terra cotta dries faster.
Indoor Light
Place in the brightest available location. Most shrubs need at least 4-6 hours of direct or bright indirect light.
Container Success Key: Match your container medium to the species needs: free-draining for xerophytes, moisture-retentive for tropical species.
7. Landscape Use & Design
Lophomyrtus obcordata is a versatile landscape plant offering structure, colour, and seasonal interest.
Design Applications
- Hedging & Screening: Dense shrubs for privacy, windbreaks, and boundary definition
- Foundation Planting: Soften building lines and define entrances
- Specimen / Accent: Showcase plants as focal points in the garden
- Mixed Border: Combine with perennials, grasses, and bulbs for year-round interest
- Topiary & Formal: Shape dense evergreens into geometric or sculptural forms
Companion Planting
- Perennials — Echinacea, Salvia, Lavandula for mixed borders
- Other Shrubs — Layer heights and textures for depth
- Grasses — Ornamental grasses add movement and contrast
- Ground Covers — Underplant with low-growing species for a finished look
Design Principle: Plant shrubs in groups of odd numbers (3, 5, 7) for natural-looking compositions. Repeat key species throughout the garden for cohesion.
8. Cold Climate Strategies
Lophomyrtus obcordata shows good cold tolerance and can be grown outdoors year-round in many temperate climates.
Hardiness Thresholds
- USDA Zones: 8-11
- Minimum Survival Temperature: -12°C (10°F)
Overwintering Options
- In-Ground Protection: Apply 10-15 cm of mulch over the root zone before first frost. Wrap trunks of borderline-hardy species with fleece.
- Container Culture: Move potted plants to a frost-free garage, conservatory, or cold greenhouse for winter.
- Microclimate Selection: Plant against south-facing walls or in sheltered spots to gain 1-2 zones of extra warmth.
Winter Survival Rule: Most shrub losses occur from late frost after spring growth has started. Avoid premature uncovering.
Frequently Asked Questions
Is this plant susceptible to myrtle rust?
Unfortunately, yes. Lophomyrtus species are among the native New Zealand plants most severely affected by myrtle rust (Austropuccinia psidii), an invasive fungal disease. Choose resistant cultivars if available and monitor plants closely, removing infected tissue immediately.
Can I grow this as a hedge?
Yes, it responds well to regular trimming and makes an attractive informal hedge 1-1.5 meters tall. Trim lightly after flowering to maintain density. The small leaves create fine texture particularly appealing in hedging applications.
Are the berries edible?
The berries are not toxic but rather bland and mealy, not particularly palatable. They're much more valuable left on the plant for ornamental effect and to provide food for native birds.
Explore More Species
Discover related species in our Shrub Encyclopedia:
Summary & Key Takeaways
Lophomyrtus obcordata, is a tree-like member of the genus Lophomyrtus (Myrtaceae), native to forests throughout New Zealand. It shows good cold tolerance, making it suitable for temperate gardens.
Key Points to Remember:
- Propagation: Cuttings or seed
- Light: Full sun to partial shade for most species
- Substrate: Well-draining, moderately fertile
- Watering: Moderate — match to species needs
- Hardiness: USDA Zones 8-11, minimum -12°C (10°F)