Sowing Seeds to Grow Pond Plants
Most flowering aquatic and bog garden plants can be grown from seed by amateurs. Plants are likely to take some time to grow to flowering size, so as a method of propagation it is really only practical where a great number of plants are required, or if you want to experiment— and you have lots of patience.
Seeds of most hybridized plants will not grow true to type. Seed sown from plants with variegated leaves, for example, may grow plants with plain green leaves. However, this is not the case with seed from species plants.
A source of free seed is to collect your own, from existing plants. Collect it when ripe, in summer or autumn usually. If it is not going to be sown immediately, it should be stored in small containers of water (yoghurt pots are fine for this).
Some plants, such as the water plantain (Alisma plantago), produce prolific amounts of seed, and in the natural habitat this seed will be carried for miles in open streams to achieve distribution of the species.
Seed of aquatic plants generally has a short life span; so sowing within a few weeks of collecting is necessary. For this reason it is not commonplace to find seed merchants offering seed of aquatic plants; this is a very different market to that of the annual and perennial flower seed industry, where dry seed can be stored and packed in sealed and clinical conditions.
If you are collecting seed of perennial bog garden plants, such as Hosta, Astilbe, arum(Zantedeschia) and so on, you can store the seed dry over winter and sow at the appropriate time, usually in late spring.
Apart from the type of compost used, and the amounts of water applied to the sown seeds, the technique for sowing aquatic plants is the same as that for garden perennials and annuals.
Fill a pot or seed tray with aquatic compost. Water it and then compress it with a small piece of flat wood. Thinly sow the seeds over the surface; it is crucial that you do not overcrowd them.
Then, to retain moisture around the seeds, sieve a thin layer of fine horticultural sand over the surface. For aquatic plants, ideally stand the container in a large tray of water, and keep the water topped up to the level of the compost. Seed of bog garden plants needs to be kept moist, but not saturated.
Place the tray in a light position, such as a greenhouse, until the seeds have germinated. When the seedlings have a pair of true leaves beyond the seed-leaves or ‘cotyledons’, prick them out into their own small pots —a tray of individual cells is fine for this. Stand the trays in water, or keep the seedlings moist, as before.
Pot the plants on when a good root system has fully developed and you can be sure that they stand a good chance. Overwinter in a frost-free place, planting the young plants out during the following spring.