Why Plant Under Crepe Myrtle Trees?
Crepe myrtle (Lagerstroemia spp.) trees are a favourite in Australian gardens for their stunning summer blooms, attractive exfoliating bark and graceful vase-shaped form. However, the area under these trees often becomes bare due to their dense canopy and surface roots. Planting underneath not only enhances the visual appeal but also suppresses weeds, improves soil health and creates a layered garden effect.
In Australia’s diverse climates—from subtropical Queensland to temperate Victoria—crepe myrtles thrive in zones 9-11, preferring full sun and well-drained soil. The challenge is selecting companions that tolerate the dappled shade, dry conditions and potential root competition once the tree matures. Focus on low-growing, drought-tolerant plants that won’t compete aggressively for water or nutrients.
Key Considerations for Underplanting Crepe Myrtles
Before planting, assess your site:
- Light levels: Young crepe myrtles offer more sun, but mature trees (over 5m tall) cast dappled shade.
- Soil and moisture: Crepe myrtles prefer slightly acidic to neutral soil (pH 5.5-7.5) and are drought-resistant once established. Choose plants with similar needs to avoid extra watering.
- Root competition: Avoid deep-rooted plants; opt for shallow-rooted groundcovers.
- Climate adaptation: In hot, dry areas like inland NSW or WA, prioritise natives. In humid tropics, select mould-resistant varieties.
- Maintenance: Mulch heavily (5-10cm deep) with organic matter like eucalyptus bark to retain moisture and deter weeds.
Prepare the area by lightly cultivating around roots, adding compost for nutrients, and watering deeply during establishment (first 6-12 months).
Top Groundcovers for Under Crepe Myrtles
Groundcovers form a living carpet, ideal for weed suppression and year-round interest.
Australian Natives
- Lomandra hystrix or Lomandra ‘Tanika’: Tough, strappy foliage tolerates dry shade and frost. Grows 30-60cm high, flowers with cream spikes in spring. Perfect for coastal or inland gardens.
- Dianella caerulea (Blue Flax Lily): Evergreen with strappy leaves and blue berries. Handles part shade, drought and poor soils. Height 40-70cm.
- Myoporum parvifolium (Creeping Myoporum): Fast-spreading mat (10-20cm high) with white star flowers. Thrives in arid zones, salt-tolerant for beachside plantings.
Exotic Options
- Mondo Grass (Ophiopogon japonicus): Fine-textured, clumping grass-like plant (20-30cm). Loves dappled shade, low water once established.
- Liriope muscari: Purple flower spikes in summer, 30-40cm high. Tolerates dry conditions and root competition.
Plant 30-50cm apart for quick coverage. In Perth or Adelaide’s Mediterranean climate, these will flourish with minimal care.
Drought-Tolerant Perennials and Grasses
Add seasonal colour without overwhelming the tree.
- Kangaroo Paw (Anigozanthos spp.) hybrids: Like ‘Bush Gems’ series, 50-80cm tall with vibrant flowers. Suited to WA and SA sands, full sun to part shade.
- Pennisetum setaceum ‘Rubrum’ (Fountain Grass): Feathery red plumes, 60-100cm. Dies back in winter but regrows; cut back annually.
- Gaura lindheimeri: Airy white/pink flowers on wand-like stems (60-90cm). Butterfly attractor, handles heatwaves.
- Sedum or Succulents: Low-growing like Sedum ‘Autumn Joy’ (30cm) for rocky textures in drier spots.
In Brisbane’s humid subtropics, choose rust-resistant varieties and ensure good airflow to prevent fungal issues.
Bulbs and Seasonal Performers
For pops of colour under crepe myrtles’ summer display:
- Nerines: Strappy leaves with pink/red blooms in autumn (40-60cm). Dormant in summer, perfect for dry shade.
- Cyclamen persicum: Winter-spring flowers in white/pink, 15-20cm. Thrives in cool-season shade.
- Daffodils (Narcissus spp.): Plant bulbs in autumn for spring show (30-50cm). Naturalise well under trees.
Space bulbs 10-15cm apart, 10cm deep. In Tasmania or cooler highlands, these extend the season.
Small Shrubs for Structure
For added height without shading the tree:
- Grevillea ‘Poorinda Constance’: Low shrub (1m) with red toothbrush flowers. Native, bird-attracting, drought-hardy.
- Westringia fruticosa ‘Naringa’: Compact grey foliage (60cm), white flowers year-round. Coastal tough.
- Callistemon ‘Little John’ (Bottlebrush): Dwarf (1m) with red brushes. Tolerates part shade.
Prune lightly to maintain shape. Avoid anything over 1.5m to preserve the tree’s form.
Design Tips for a Stunning Underplanting
- Layering: Tallest at the base transitioning to groundcovers. E.g., Grevillea > Dianella > Lomandra.
- Colour echo: Pair crepe myrtle’s pink/purple blooms with complementary perennials like salvias.
- Container option: For root-heavy areas, use pots with Brachyscome or Scaevola.
- Pest management: Watch for aphids on new growth; natives deter most issues.
| Plant Type | Height | Water Needs | Best Climate |
|---|---|---|---|
| Lomandra | 30-60cm | Low | All Aus |
| Dianella | 40-70cm | Low-Med | Coastal |
| Myoporum | 10-20cm | Very Low | Arid |
| Nerine | 40-60cm | Low | Temperate |
Maintenance and Common Mistakes
- Watering: Deep water weekly first summer, then only in extreme drought.
- Fertilising: Slow-release native fertiliser in spring (e.g., 10-5-10 NPK).
- Weeding: Hand-pull initially; mulch prevents regrowth.
Avoid: Water-loving plants like ferns (too wet), thirsty lawn grasses or invasive species like gazanias in bush areas.
In Melbourne’s variable weather, protect new plantings from frost with covers. Over time, this underplanting creates a low-maintenance, vibrant base that showcases your crepe myrtle’s beauty.
Regional Spotlights
- Queensland/Tropics: Lomandra, Dianella; avoid frost-tender exotics.
- Sydney/Coastal NSW: Myoporum, Westringia for salt spray.
- Inland/Victoria: Kangaroo Paw, Sedum for dry heat.
- WA Dry Zones: Grevillea, Pennisetum.
Experiment with combinations suited to your microclimate. With thoughtful selection, your crepe myrtle garden will thrive for years, providing habitat for native bees and birds.
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