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.
Timing of propagation depends on the method;
How to propagate pond plants
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)
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.
The name pondweed refers to the 80 or so species of aquatic plants belonging to the genus Potamogenton. They vary in size and appearance so much that it’s hard to describe a typical pondweed. Some are totally submerged under the water, while others are only partly submerged. The plants are an important part of the pond’s ecosystem, and they can be ornamental in the right setting. They serve as a valuable wildlife food as well as an oxygenator that helps keep the pond in balance. When out of control, however, the plants can choke the life out of a pond, and then it’s time take steps in controlling pondweed plants.
How to Control Pondweed
Where herbicides for lawns and gardens are usually chosen based on the weed you are trying to kill, herbicides for ponds are tailored to the site. Read the label carefully before you choose, paying special attention to precautions, restrictions and intended use. Use the least toxic herbicide to protect the fish and other wildlife in your pond and preserve enough plants to support them. Herbicides containing the active ingredient endothall are a good choice for controlling pondweed.
Before you use herbicides, there are a couple of other pondweed control methods that are worth considering. Prevention is the best method of control, so think carefully before you plant. If you decide to plant them, use containers to hold the roots rather than in the mud at the bottom of the pond.