- 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
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.
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 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.
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.
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)