How to Correctly Plant NZ Native Groundcovers on a Steep Bank

Planting native groundcovers on a steep bank is one of the smartest long-term solutions for erosion control and low-maintenance landscaping in New Zealand. With the right species selection, site preparation, and planting technique, you can establish a resilient, attractive slope that looks after itself. Here's a practical guide to getting it done properly.

Why Native Groundcovers Work So Well on Banks

NZ native plants are adapted to our soils, rainfall patterns, and climate extremes — from the wet winters of the West Coast to the dry nor'westers of Canterbury. Their root systems are often deep and fibrous, which is exactly what you need to bind soil on a steep slope. Native groundcovers also support local birds and insects, and once established, they generally need far less water and fertiliser than exotic alternatives.

For guidance on plant selection suited to your region, BRANZ and local councils often publish planting guides for erosion-prone sites.

Choosing the Right Species

Not all natives suit every bank. Consider your slope's aspect (sun or shade), soil type, rainfall, and steepness before choosing. Here are some well-proven options:

Always source plants from a reputable native nursery to ensure you're getting the correct species and, where possible, local provenance plants — these are genetically suited to your area and will establish more successfully.

Assessing Your Bank Before You Start

Before planting, take a good look at the slope:

• Gradient: Banks steeper than roughly 35–40 degrees may need engineering solutions (retaining walls, geotextile mesh, or rock armouring) before or alongside planting. If in doubt, consult a qualified landscaper or geotechnical engineer.
• Soil stability: If the bank is actively slipping or has deep erosion channels, planting alone won't fix it. Seek professional advice first.
• Drainage: Waterlogged soil at the base of a bank can undermine stability. Check whether drainage improvements are needed.
• Existing vegetation: Remove invasive weeds thoroughly before planting — kikuyu, tradescantia, and woolly nightshade are common culprits that will outcompete young natives if left unchecked.

Site Preparation

Good preparation makes the difference between plants that thrive and plants that struggle:

1. Weed control: Spray or hand-remove all weeds. For persistent species, you may need two or three rounds of treatment over several weeks before planting.
2. Soil loosening: On compacted banks, use a mattock or fork to loosen planting pockets — this helps roots establish quickly.
3. Erosion control fabric: On very steep or bare banks, consider laying a biodegradable jute or coir erosion control mat over the soil before planting through it. This holds the soil while plants establish and breaks down naturally over time.
4. Mulch: Apply a 50–75 mm layer of coarse wood chip or bark mulch around (not over) each plant. On a slope, use pegged mulch mats or plant through the erosion fabric to stop mulch washing away.

Planting Technique on a Slope

Planting on a bank requires a slightly different approach to flat ground:

• Create a level planting pocket: Use a mattock to cut a small flat shelf into the slope for each plant. This prevents water from running straight past the root zone.
• Plant at the correct depth: Set plants at the same depth they were in the pot — no deeper, no shallower.
• Angle the plant slightly uphill: This encourages roots to grow into the bank rather than outward.
• Water in well: Even drought-tolerant natives need consistent moisture for the first season. Water each plant thoroughly at planting, then regularly through the first summer.
• Spacing: For groundcovers, plant at 300–600 mm centres depending on species. Closer spacing means faster coverage but higher initial cost.
• Stagger your rows: Plant in a zigzag pattern across the slope — this gives better coverage and reduces erosion channels between rows.

Aftercare and Establishment

The first 12–18 months are critical:

• Watering: Water deeply once or twice a week in dry spells during the first summer. Avoid light, frequent watering — it encourages shallow roots.
• Weed control: Check regularly and remove any weeds by hand before they set seed. This is especially important in the first two seasons.
• Fertilising: Native plants generally prefer low-nutrient conditions. If you do fertilise, use a slow-release fertiliser formulated for natives — standard garden fertilisers can burn sensitive root systems.
• Top up mulch as needed to maintain coverage and suppress weeds.

Once established — typically after two full growing seasons — most NZ native groundcovers will largely look after themselves, spreading to fill gaps and suppressing weeds naturally.

When to Call a Professional

While planting groundcovers is a DIY-friendly project, there are situations where you should bring in a qualified landscaper or other specialist:

• Steep or unstable banks where there's a risk of slippage — a geotechnical engineer or experienced landscaper should assess the site first.
• Large-scale projects where erosion control fabric, retaining structures, or drainage work is needed.
• Consenting requirements: Some earthworks and retaining walls require a building consent under the NZ Building Code. Check with your local council before undertaking significant earthworks — Schedule 1 exemptions apply in some cases but rules vary by council and site.
• Proximity to waterways: Planting near streams or wetlands may be subject to regional council rules under the Resource Management Act. Check with your regional council before starting work.

You can find qualified, experienced local landscapers on tradedirectory.co.nz who can assess your bank and recommend the best approach.

Sources & Further Reading

• BRANZ – Building Research Association of NZ
• MBIE Building Performance – Building Consent information
• WorkSafe NZ – Safe working on slopes
• Energywise – Sustainable landscaping tips
• Standards NZ