If you own an outdoor pond, you have probably thought about putting some type of aquatic based plants inside it to create a more natural looking environment. However, like outdoor gardening, water based plants present their own unique challenges and can be very temperamental. You have to put certain plants in certain water depths, along with the water temperature being just right and then there is winter weather to consider, especially if you live in the northern part of the United States where you pond is likely to partially freeze during those months.
And believe it or not, you are still planting everything even though it is underwater and that requires the right type of soil and container size for the plants to prosper.
In fact, you should not be using regular potting soil to plant your aquatic plants in containers. Most commercial potting soils are too lightweight and do not hold nutrients long enough for the plants to absorb.
When someone mentions aquatic plants, the first thing that usually comes to mind for most people is water lilies. While they are the most popular choice for outdoor ponds, there are many other water based plants that are suitable for garden ponds. The idea is to create interest in your pond with a variety of plants in and around it.
However, why not begin with the most popular choice?
There are hundreds of different types of water lilies but all are classified in one of two groups: hardy and tropical. All types of water lilies do best when they are planted in heavy clay soil similar to what you would see in a garden setting although once again, you should not use commercially available potting soil.
Both types include shade tolerant varieties that only need about 4 hours of sunlight a day. As a general rule though, the more sunlight the better. Most varieties require at least 6 hours of direct sunlight at a minimum.
As you may have guessed, hardy lilies are cold weather resistant and can endure the frost within reason. They do so by dying back to their roots during the cold winters and spring back to life when it warms. In warmer climates that do not have frosty winters, they stay leafy year round.
Hardy water lilies are tolerant of cooler water temperatures and do well in ponds when the water temperature is about 50 degrees.
Whether you realize it or not, you have probably seen hardy lilies in a pond or outdoor garden. They are the type of lilies with large blossoms that float on the surface of the water. Sometimes they rise slightly above the water level especially if they are blooming, but they never reach the height of tropical lilies.
Tropical lilies do not do well in cold weather and will more than likely die if exposed to more than one frost. Tropical lilies tend to do well year round in warmer climates such as southern California or Florida. They should not be placed in the pond until the water temperature reaches at least 70 degrees.
If you are intent on using them in other parts of the country, you will have to put them up during the winter months, typically a green house or extremely warm setting. Since most people do not own a green house, you can see how this would be a problem.
So if they are so much more of a hassle and die off each year in most of the country, why do people even bother with the tropical variety?
Well, one advantage they have over hardy lilies is their smell. They have a strong flowery fragrance and their blossoms stand up higher out of the pond water.
There are also night blooming tropical varieties which open their blooms at dusk and close them mid-morning.
How to Plant Water Lilies
Water lilies are usually the first type of water based plants that most garden centers have each year so most pond owners start with them. When you go to buy them, you will not get a full leafy plant. Instead you will receive a piece of rootstock officially called a rhizome for hardy lilies and a tuber for tropical lilies. Try to plant them early in the Spring so that they have time to establish themselves before the warm summer growing season.
Using wide, shallow containers specifically designed for them if possible, fill each one half full with heavy loam garden soil. If you are using a plant basket, line it first with burlap to prevent the soil from washing away.
Once again, do not use commercial potting soil, or mulch peat moss, compost or ordinary gardening fertilizer. There are specially designed fertilizer tablet available for water based plants if you want to go in that direction. The recommended rate for water lilies is four ounces of fertilizer for every one cubic foot of soil mixed into the soil.
Place the rootstock of hardy lilies horizontally with the crown or growing tips near the eges of the container. Allow for plenty of room for them to expand. For tropical lilies, place the rootstock vertically in the center of the container.
Now that the lilies are in place in the container, fill it with soil to a level just beneath the crown and top that off with pea gravel to hold the soil in place and protect the roots from fish (if any).
Placing the Lilies
For tropical lilies, submerge the container so that the crown or growing point of the plant is 6 to 12 inches below the water line. If you are placing hardy lilies, the tip can be anywhere from 6 to 24 inches from the surface of the water. If the pond has less than 6 hours of direct sunlight each day, then the closer you place the plant to the surface, the better.
At times during the year, you may want to divide and re-pot the lilies to make more. At that time, consider adding a fertilizer tablet each time.
Storing Water Lilies for the Winter
Hardy lilies in shallow ponds and water gardens in most areas of the country should be brought inside for the winter months. Simply lift the containers from the pond and trim off any dead leaves Wrap a plastic bag around the plant to help it keep its moisture and store it in an area that is at least 50 degree even during the coldest winter months.
If you have an insulated garage, that would be a good place as it would not go below that temperature typically. At various times during the winter months, look inside the bags and make sure it still has moisture inside.
Tropical water lilies are stored a little different. Remove these from the pond in the same manner and trim off most of the leaves and roots. Then repot it into a smaller container and store it in warm water in an aquarium tank with plenty of sunlight and the temperature stays above 70 degrees.
These types of plants grow entirely underwater as the name suggests. So why would you want to bother with a plant you may not be able to see?
Well, they play an important role in the ecology of your pond because they oxygenate the water. They also provide food and a place to hide for fish if you have any.
Some of these types of plants look very similar to the ones you have probably seen in indoorCredit: Opensource fish aquariums. I have used the long fern looking anarcharia variety many times myself. Other common types of submerged plants include cabomba which has leaves shaped like fans made of hair, and a type of ribbon grass called vallisneria with long ribbon like leave.
How to Plant Submerged Plants
Once again, you will use a container spread with the appropriate soil, then place the plant inside under a thin layer of the soil. Next, add a thin layer of pea gravel to keep the plant in place. If you have ever owned a fish aquarium, you probably have experience doing this.
Place the container inside the pond making sure to allow enough room to grow underwater. These types of plants can grow up to 30 inches and do best if the top leaves are submerged in 6 to 12 inches of water.
If you have fish in your outdoor pond, you might want to consider protecting it initially from them since they like to graze on the plants, especially anacharis. To keep a temporary barrier, take a lightweight plastic mesh such as bird netting and wrap it around the container allowing for about 10 inches of the material to extend above the rim of the container. Close the sides and the top of the mesh off with twist ties. You can remove this later when the submerged plant has established itself.
These plants float as their name implies. Imagine that? Actually, it is the buoyancy of their leaves that keep them floating so they may not float when they are young.
However, once hovering at the top of the water, their roots will dangle underneath and thus require no planting or soil.
Floating plants add to the natural look of any pond while providing shade and a place to hide for fish. Some of the more common varieties are water lettuce, water fern and duckweed. They require no special planting procedure and are considered hardy in warmer climates but annuals in colder climate where they are killed by winter frost.
The biggest downside to floating plants is that they have a tendency to take over during the summer months if you are not careful. Occasional pruning or even removal will take care of this issue though. Also as mentioned before, if you have a lot of fish in your pond, they will eat many varieties of aquatic plants.
Water based plants can add to the natural look of any outdoor pond. In fact, if you are serious about creating a natural looking environment complete with live fish, plants are essential for the oxygenation of the water and providing a source of food and comfort for any wildlife in the pond.
Aquatic based plants are easy to prepare and place in outdoor ponds and require little to no maintenance throughout the year. During the winter months, you will need to move some types such as lilies indoors, but other are simply treated as annuals and die off in most areas of the United States.
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