The fragrance of a water lily blossom, the contrast of variegated foliage, the filtration qualities of Water Hyacinth; these are just the beginning of the benefits of plants in your water garden. To many, aquatic plants are the highlight of their garden. But, I am often asked about selecting the right plants.
Aquatic plants have many functions in the water garden. The obvious is that they provide beauty. The foliage and flowers offer the finishing touches to complete a dazzling aquatic display.
Pondkeepers with an understanding of filtration know the nitrification cycle and how plants play their role. Fish naturally secrete ammonia into the pond water. Biological filtration works to convert the ammonia into nitrites then the nitrites into nitrates. The nitrates are then used by the plants. If there are not enough plants using up the nitrates in your pond, you end up with an algae bloom (in extreme cases of nitrate buildup the fish may suffer as well). Plants that cover the pond surface also reduce algae by limiting the amount of sunlight reaching the water. For the best balance in a water garden around 2/3 of the pond surface should be covered with plant foliage.
Another, often overlooked, use of plants in the pond is protecting your fish from hungry predators. Whether it is tall plants at the water's edge that help prevent a raccoon from reaching the pond or the water lily pads covering the surface that give the fish a place to hide from a heron, a few plants may be all that is needed to avoid making a meal out of your pet fish.
When it comes to actually selecting the plants for your pond, there is nothing more important than your eyes. That's right, while there are certain types of plants that you may want as we will discuss in a moment, choosing plants that you think look good is the most effective way to get a water garden to be proud of.
LOTUS: Lotus leaves grow atop stems that are attached to the tuber in the soil (the first leaves of spring will float on the surface like water lily leaves). The leaves can be 12- 24" in diameter and 2 - 5' above the water. The flowers, which appear generally June through August come in variations of white, yellow, and pink. When the flower has finished it leaves a brown seed pod. These are commonly used in dried flower arrangements. Lotus are generally hardy to USDA zone 5 and prefer full sun.
HARDY WATER LILIES : Lily pads rest on the water surface (when crowded some pads rise slightly above the water). They are attached to the rhizome via long stems. In hardy lilies these pads are mostly all green, some varieties have light mottling and new leaves of many hybrids emerge with a red color. The flowers, which appear in summer, also float on the surface, some hybrids have flowers that will rise a few inches above the water. Flower colors in hardy lilies include white, yellow, pink, peach, red, and variations of each. Hardy lilies go dormant in the winter and return in the spring provided that the rhizome did not freeze. Hardy lilies generally do best when placed with the crown of the plant around 12" below the water's surface.
TROPICAL WATER LILIES : Tropical water lilies offer some characteristics not available in hardy varieties. Blue flowers and purple flowers are only an option with tropical water lilies. There are also night-blooming varieties. The flowers on these open around dusk and stay open until mid-morning. The flowers of tropical water lilies rise several inches above the surface of the water. They are also more prolific and more fragrant. Tropical lilies need water temperatures in the 70s, so they cannot go out in spring as early as their hardy cousins. While they will not survive outdoors except in very limited warm areas of the country, their benefits still make them worth a try in most water gardens. Just because they don't survive your winter does not make them unsuitable as an annual plant to have just for the season. Tropical water lilies don't like to be quite as deep as hardies, having the crown 8-10" below the water surface is great.
SHALLOW-WATER PLANTS : Often called "marginal plants", these plants are typically placed in more shallow areas of the pond. Most ponds are built with a plant shelf at around 12" deep specifically for placing shallow-water plants. There are hundreds of varieties of plants that go in this group. Looking at sun requirements and growing height will help you choose the right plants for your pond. But, again, please don't underestimate your own preference. Pick the plants you like and you are bound to be happy with the decision. There are shallow-water plants that will survive anywhere in the country and those that will survive in only limited areas. Just like tropical lilies, a plant that doesn't survive the winter can still make a wonderful choice to keep for one season.
LILY-LIKE PLANTS : As you might gather from the name, these plants grow in a similar fashion to water lilies. That is that they are rooted in soil, with leaves floating on the water surface attached to the roots with a long stem. These are also a great way to get some surface coverage without a lily. Some, like 4-Leaf Clover, tolerate very low-light conditions and thus make a good alternative when a lily is not the right choice.
FLOATING PLANTS : Floating plants are simply plants that free-float and do not need to be anchored in a pot. It doesn't get much easier than that. Floaters are generally very prolific. Many states are beginning to ban these as they become problems in natural waterways. Responsible water gardening includes keeping plants contained within the water garden. If your state allows these plants, they are extremely beneficial to the pond. They not only shade the surface, but with their roots hanging in the water, they pull a great deal of nutrient from the water reducing algae growth.
UNDERWATER PLANTS : Underwater grasses are the staple of the backyard pond. The most common is Anacharis. These plants grow completely submerged (although the growth of most will end up reaching the surface). We place these in pots of pea gravel to hold them in place. This keeps them anchored and keeps the pond looking neater. These plants are an excellent way to remove nutrients from the water.
Placing Aquatic Plants
So you have finally chosen the plants to complete your water garden. Now you need to determine where to place them and how to get the most aesthetic benefit from what you have. When doing this, it is important to remember that plants grow. This means you want to plant them in large pots to give them room to spread out. It also means you may not need quite as many plants as you think (unless you give in to instant gratification). Try to picture how the plants will look once established while planning the layout in the pond.
With most ponds, you have one main area that the pond is enjoyed from. Think about this as you are placing your plants. Don't place a 4' tall cattail in front of a low-growing Water Mint.
Think about the moving water. Water lilies, in particular, do not tolerate a direct splash and do best in an area of the pond with less movement.
Don't be afraid to experiment. There is nothing that says each pot can only have one type of plant in it. Place multiple types of shallow-water plants in the same pot for a new look. And vice-versa, just because you have room for 6 shallow water plants, doesn't mean you need 6 different varieties. Try 3 of one and 3 of another. Then you decide if you want to group the like kinds or alternate.
Planting themes can be a fun way to make your pond standout. Maybe you want only plants with variegated leaves. Or, perhaps you only want plants with red flowers.
Once your pond has been planted, your plants just need a little basic care to provide you with everything you had hoped for. Trim off foliage as it yellows or browns, fertilize on a regular basis, and divide plants that are getting too large for their pot.
While, we have given some suggestions on how to choose some plants, remember that this is your pond and you can't go too wrong. So, give it your personal touch by choosing plants that you will enjoy looking at.