One of my favorite aspects of water gardening, throughout the seasons, is witnessing the growth of lush plants in and around the pond and the ever-changing colors they bring. I like to get to my favorite garden center early in the season when the selection is good. Planting early in the season also allows the new additions a head start for growth.
Pond plants are not demanding; they generally need less maintenance and attention than plants in other areas of your garden. They are beautiful as well as functional. For example, deep-water plants such as lotus or water lilies produce gorgeous flowers, and the leaves provide shade that keeps algae in check as well as provide protection for your fish. When repotting a new lily, work in the shade as the leaves can quickly dry when out of the water and in the sun. If the plant is large, sometimes it's helpful to get an extra hand to hold the long-stemmed leaves to keep them from being damaged. Water lilies do best in a calmer section of your pond and away from a fountain. Too much agitation and water on top of the leaves will cause them to turn yellow and eventually rot. Lotus and lilies require fertilizing; fish-safe tablets are readily available from your local water garden supplier.
Submerged aquatic plants are key to maintaining clear water, not to mention a good hiding place for small fry (sometimes too good, I now have way too many baby Koi). Unlike other plants that absorb nutrients through their roots, aquatic plants absorb through their leaves and in turn, starve out algae. Also known as oxygenators, they release oxygen into the water during the day, which is beneficial especially if you have fish. Just be careful; too many plants in the bottom of the pond have a negative effect of releasing too much carbon dioxide during the evening, so keep growth in check. Submerged plants do not need soil and can be anchored in a low pot or tray of 1"-2" of sand or gravel. Fertilizing submerged plants is not necessary.
Each spring I am amazed at how much growth occurs with my irises in just one season. It's not unusual to find the plant twice as wide as the pot! I'll spend an afternoon in early spring bringing the submerged plants up from the bottom, splitting them up and before I know it, I have four plants where I had one. I use a heavy mix of garden soil and clay, replant the iris roots and cover the top with gravel. This keeps the soil in place and also adds weight. Never use soil that contains compost or organic matter.
During the season, pinch and prune dead leaves and spent flowers whenever you can. Pinch off long stems as close to the base as possible. Remember, if the water is healthy, generally the plants will be healthy. If you see insects such as caterpillars or aphids, pick them off, remove the leaves, or better yet, if you have fish, simply shake the plant under water and it's a snack.