Plants are one of the most important components of a healthy ecosystem pond - and one of the most underestimated. Most people think about plants as decoration. In a properly built ecosystem pond, they're doing real biological work: competing with algae for nutrients, oxygenating the water, providing habitat, and helping the whole system find its natural balance.
Get the planting right and your pond becomes easier to maintain as it matures. Get it wrong - or skip it entirely - and you're fighting algae and water quality issues indefinitely.
Here's what to plant and why it matters.
Why Plants Matter in an Ecosystem Pond
An Aquascape ecosystem pond works through biological balance - beneficial bacteria, aquatic plants, fish and filtration all working together the way nature intended. Plants play three key roles in that balance:
Nutrient competition - aquatic plants absorb the same nutrients algae feeds on - primarily nitrogen and phosphorus from fish waste and organic debris. More plants means less food for algae, which means clearer water with less intervention.
Oxygenation - submerged plants produce oxygen directly into the water, supporting fish health and beneficial bacteria that live on the pond floor and in the filter media.
Habitat and shelter - plants provide shade, hiding spots for fish, and landing places for beneficial insects and wildlife. A well-planted pond attracts far more life than a bare one.
We recommend 40-60% of your pond's surface area be covered by plants at maturity - a mix of water lilies providing surface coverage and marginal plants softening the edges.
The Four Types of Aquatic Plants
1. Water Lilies
Water lilies are the centrepiece of most ecosystem ponds and the single most important plant for surface coverage. Their broad floating leaves shade the water beneath, reducing light penetration and directly limiting algae growth. They also produce flowers through the warmer months - one of the most rewarding things about a well-established pond.
Hardy water lilies are the best choice for New Zealand conditions - they die back in winter and re-emerge in spring, handling Canterbury's frosts without issue. Tropical water lilies are available but require more care in cooler climates.
Water lilies are best planted in Aquascape's dedicated lily planter bags - specifically designed for aquatic use, they allow roots to develop naturally while keeping soil contained and preventing it from clouding the water.
Good varieties available in NZ:
Nymphaea 'Attraction' - deep red flowers, reliable performer in Canterbury conditions
Nymphaea 'Marliacea Albida' - white flowers, strong grower, good surface coverage
Nymphaea 'Chromatella' - pale yellow flowers, one of the most popular hardy varieties
Nymphaea 'James Brydon' - deep pink-red, compact growth suitable for smaller ponds
Position water lilies in the deeper zones of the pond - 300-600mm of water over the crown is ideal.
2. Marginal Plants
Marginal plants grow at the edges of the pond in the shallower shelf areas - typically in 50-150mm of water. Rather than being planted in pots or baskets, they're planted directly into the gravel substrate on the pond shelf, allowing their roots to spread naturally and contribute directly to biological filtration by absorbing nutrients from the water.
They soften the transition between water and land, provide habitat for beneficial insects, and are what gives a pond its established, natural look - the difference between a pond that looks like it was installed last week and one that looks like it belongs.
Good marginals available in NZ:
Iris laevigata (Japanese Water Iris) - one of the most reliable pond margins in NZ. Purple-blue flowers in spring, upright strap-like foliage that looks good year-round. Handles Canterbury conditions well.
Pontederia cordata (Pickerelweed) - blue-purple flower spikes through summer, heart-shaped leaves. Strong grower, good for wildlife.
Acorus gramineus (Japanese Rush) - low-growing, grass-like foliage. Works well at the very edge of the pond and between rocks. Variegated forms add visual interest.
Typha (Raupo/Bulrush) - NZ native, excellent for larger ponds. Provides strong vertical structure and significant nutrient uptake. Can be vigorous - dwarf varieties (Typha minima) are better suited to smaller ponds.
Myosotis scorpioides (Water Forget-Me-Not) - low-growing, blue flowers, spreads naturally along the water's edge. Good for softening rock edges.
Zantedeschia (Arum Lily) - bold white flowers and striking foliage at pond margins. Note: classified as an environmental weed in some Canterbury regions - check local guidelines and avoid planting near natural waterways.
3. Submerged Oxygenating Plants
Submerged plants - also called oxygenators - grow entirely underwater. They produce oxygen, absorb nutrients directly from the water column, and provide spawning habitat and shelter for fish. They're not showy - you often can't see them from a distance - but they're doing more biological work than almost any other plant in the pond.
Important note for NZ pond owners: several commonly available submerged plants are classified as Unwanted Organisms under the Biosecurity Act 1993. It is illegal to sell, propagate or spread these species. Always purchase oxygenating plants from a reputable NZ aquatic nursery and verify that what you're buying is not listed on the MPI Unwanted Organisms Register before introducing it to your pond.
Good oxygenators available in NZ:
Potamogeton (Pondweed) - native NZ aquatic plant with ribbon-like submerged leaves. A safe and effective oxygenator that provides good fish habitat. Available from reputable NZ aquatic nurseries.
Vallisneria (Eel Grass) - long, ribbon-like leaves, excellent for larger ponds. Provides consistent oxygenation and good fish habitat.
Myriophyllum (Milfoil) - feathery submerged foliage, good oxygenator. Several species available in NZ - some exotic milfoils are restricted, so confirm the variety is compliant before purchasing.
4. Surface Coverage
Water lilies are by far the best choice for surface coverage in a Canterbury garden pond - they provide shade, nutrient uptake and flowering interest all in one plant. Aim for 40-60% surface coverage at maturity across the whole pond using water lilies as your primary surface plant.
Many floating plants sold for ponds are restricted or potentially invasive in NZ. Water lilies are the safe, effective, and beautiful choice - and they're better suited to Canterbury's cooler winters than most floating alternatives.
Planting for Canterbury Conditions
Canterbury's climate presents specific considerations for aquatic planting:
Nor'west wind - exposed ponds can lose significant water to evaporation and have plants stressed by hot, dry nor'west conditions. Shelter planting around the pond perimeter helps, and choosing robust varieties over delicate ones pays off.
Frosts - hardy water lilies handle Canterbury frosts well, dying back in winter and re-emerging strongly in spring. Tropical varieties are a higher-maintenance choice in this climate.
Temperature swings - Canterbury's significant difference between summer and winter temperatures suits hardy marginals and oxygenators that go dormant in winter rather than tender varieties that need protection.
UV intensity - New Zealand's high UV environment means plants establish quickly in summer but can also stress easily. Adequate water depth and surface coverage help moderate temperature and UV at the pond surface.
How Many Plants Do You Need?
As a starting guide for a newly built pond:
Water lilies - one plant per 2-3m² of surface area
Marginals - 3-5 plants per metre of pond edge, varying heights and textures
Oxygenators - one bunch per 0.5m² of pond surface area
Surface coverage target - 40-60% of total pond surface at maturity
A new pond will look sparse at first - that's normal. Plants establish quickly through the first growing season and the pond will look significantly fuller by the end of its first summer. Resist the urge to overplant at the start - you'll be dividing and thinning within a year or two of a well-planted pond.
Planting and Maintenance Tips
Plant water lilies in Aquascape lily planter bags with heavy loam or clay-based aquatic compost - not standard potting mix which floats and clouds the water
Top lily planters with pea gravel to hold soil in place
Plant marginals directly into the gravel substrate on the pond shelf - no pots needed
Feed water lilies with aquatic fertiliser tablets pushed into the planter bag soil - not liquid fertiliser which feeds algae directly
Divide water lilies every 2-3 years when they become congested
Cut back marginals in autumn as they die down - removing dead material before it decomposes in the pond reduces nutrient load
Plants and the Ecosystem
A well-planted pond is a genuinely different experience to a sparse one. The biological balance is more stable, the water is clearer, the wildlife is more abundant, and the feature looks established and intentional rather than bare and artificial.
Every Southern Waterscapes ecosystem pond build includes aquatic and marginal planting selected for the specific pond size and site - we source from reputable NZ aquatic nurseries and plant for biological balance as well as aesthetics.
If you're planning a pond and want to talk through planting as part of the design, get in touch - it's one of our favourite parts of the process.
Southern Waterscapes Ltd - New Zealand's only Certified Aquascape Contractor, based in Rolleston, Canterbury.