Like any other plants, water plants should be clean, fresh-looking and vigorous. Look for specimens that are growing in tanks that are free from duckweed and algae to avoid introducing them into your pond. Also check the plants to see if the undersides of the leaves are free from jelly-like deposits of snails or whelk eggs and that there are no strands of blanket-weed in the foliage. Once you will involuntary introduce these to you pond it will be hard to get rid of them.
Beside the plants grown in tanks you can find vacuum-packed plants. When you buy them make sure they look plump and green. If they look weak and limp they will not develop well so avoid buying them. You pond plants should be as healthy as you can buy. If you don’t find anything appropriate just go and buy plants from another supplier.
A good supplier or nursery will also be able to advise you on how many plants you should buy for you pond in order to achieve the required delicate balance between submerged, oxygenating plants and floating-leaved plants. You should know that the floating plants should cover one third to half of the water surface to provide some shelter from the sun.
There is the possibility to buy plants by mail order. In this case make sure you find a specialist supplier. You will pay a higher price but you will be sure that the plants you buy are disease-free and have been propagated in the nursery. Also a reputable supplier should pack the plants with care and dispatch them on the same day they are lifted. This way you have the guarantee of healthy plants.
When buying oxygenators for a new pond, consider about five bunches for every square meter or yard of water surface. These plants are generally sold individually as small, weighted, fiber plugs, which can just be thrown on the water. Also some of them are sold as bunches of unrooted cuttings of about 23 cm long. The lead clasp that is used for holding the bunches together is heavy enough to pull the plants down to the bottom of the pond. Once there, the cuttings will root.
When buying oxygenators plants make sure you keep them moistened in a plastic bag or submerged in water until you are going to plant them in the pond because they are extremely susceptible to drying out if left without water while they wait to be planted.