As well as increasing stock, propagation is an excellent way to promote fresh young growth in your pond plants while discarding the older, unproductive plant parts.

• Most pond plants can be divided, including: Nymphaea (waterlilies) and especially marginals such as Butomus umbellatus AGM (flowering rush), Caltha palustris AGM (marsh marigold), Iris laevigata AGM (Japanese water iris), Pontadera cordata AGM and Schoenoplectus lacustris (bulrush)
• Submerged oxygenators and creeping marginals can be propagated by cuttings. Examples include: Hottonia palustris (water violet) and Ranunculus aquatilis (water buttercup)
• Floating plants including Eichhornia crassipes (water hyacinth) and Hydrocharis morsus-ranae (frog-bit) naturally produce runners, plantlets or turions in the form of swollen detachable buds
• Pond edge
  Perennials are any plant living for at least three years. The term is also commonly used for herbaceous perennials which grow for many years (To compare: annual = one year, biennial = two years).

  perennials and bog plants can be divided such as Astilbe chinensis var. pumila AGM, Filipendula ulmaria, Iris ensata AGM, Ligularia dentata ‘Desdemona’ AGM and Lythrum salicaria
• Some aquatics and moisture-loving pond edge perennials can be seed raised as well as increased by division. Examples include Aponogeton distachyos (water hawthorn), Lobelia siphilitica, Cardamine pratensis (lady’s smock)

Timing of propagation depends on the method;

• Divide clumps of fibrous-rooted, tuberous-rooted and rhizomatous plants when in active growth in spring
• Cuttings, root-bud cuttings and stem cuttings can be taken in spring and summer to produce young plants to be grown on under glass until danger of frosts has passed
• Collect seed when ripe in summer or autumn. Seeds can also be obtained in specialist nurseries. Note: seed of cultivars may not grow true to type

Division

• Divide plants with fibrous or creeping roots, such as sedges and reeds, in spring. Pull roots apart by hand or use two garden forks back-to-back and lever apart. Each division should have a growing point
• Cut off old leaves and roots then trim new roots before replanting in individual containers. Top dress with gravel and cover the container with 5-7.5cm (2-3in) of water
• Pull apart plants with strong rhizomes, such as iris. Use a sharp knife to divide into sections, each with at least one bud and some young roots. Trim foliage and long roots then replant with the rhizome almost exposed
• For waterlilies, cut the rhizomes into sections with two or three growth buds

Cuttings

Take healthy, young shoots from oxygenators and insert into pots of loam or aquatic plant potting media. Submerge the pots. Cuttings establish quickly and may be potted on after two or three weeks.

Root-bud cuttings

Waterlilies and tuberous plants, such as Acorus, can be propagated from root-bud cuttings from the rhizome. They may produce tiny, new growing points on the roots where shoots emerge. Cut off a 7.5cm (3in) piece of the root behind the growing point. Pot up and grow on.

Bulbils

Bulbils of plants such as Butomus umbellatus (flowering rush) are simply detached. Pot up and keep just submerged.

Runners and plantlets:

Floating plants, such as Eichhornia crassipes (water hyacinth), produce plantlets. These can be snapped off in early summer and placed on the water surface to grow on separately.

Turions

Some water plants, such as Hottonia palustris (water violet) and Hydrocharis morsus-ranae (frog-bit), produce turions. These are swollen nodule-like root buds that become detached from the parent plant and survive winter at the bottom of the pond. Emerging buds float to the surface in spring and naturally start into growth. They can also be collected, potted up and grown on.

Seed

Sow seed as soon as it is ripe. Use pots filled with aquatic compost and sow seed on the surface, covering with a thin layer of grit. Just submerge the container and place in a well-lit situation. Seed should germinate the following spring but may take three or four years to flower. Germination may be easier with bottom heat of about 18°C (65°F). Pond plants ideal for seed raising include Ranunculus lingua ‘Grandiflorus’ (greater spearwort) or Glyceria maxima var. variegata (variegated water grass)

There are not many problems to watch out for, but the following may be troublesome at times:

• Invasive non-native plants: Choose your pond plants for propagation carefully, as invasive species can be difficult to control once established. Never dispose of any unwanted pond plants in the wild. Fast growing aquatic weeds such as Crassula helmsii (New Zealand pygmyweed), Lagerosiphon major (curly waterweed) and Elodea canadensis (Canadian pondweed) can all get out of hand where conditions are favourable
• Slugs and snails can quickly eat through young marginals and moisture-loving plants. Water snails may be a problem for submerged plants
• Powdery mildew can affect some soft-stemmed marginals and pond plants encouraged by overcrowding and humid or damp air
• Bog plants such as hosta, primula and astilbe are vulnerable to vine weevil damage to the roots