Repotting and fertilizing pond plants

Aquatic plants are one of our favorite subjects.  These beautiful additions to your landscape do more than just look good with their vibrant flowers and unique shapes, they also play a vital role in the natural balance of your pond's ecosystem.  
There are many types of pond plants you can choose for your water garden.  They can be grouped into four main categories: water lilies, floaters, oxygenators, and marginals.  

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Wanvisa Water Lily

Most pond plants will need to be repotted after purchasing.  Generally, the bigger the pot, the better the plants will do.  The plant will also look more natural as it grows into the larger pot.  In contrast, smaller pots are much more likely to fall over, they rarely look natural, and they are prone to becoming root-bound.  

Water lilies provide shade, shelter, and a natural environment for fish, frogs, and other small creatures living in your pond.  Most water lilies, when purchased from a garden center or big box store, are sold as a bare tuber that's been dry-potted in a regular 10" landscape pot.  They basically resemble a turnip with some thin, stringy roots and a few dried stubs of stems poking out the top.  Lilies are packaged like that because it's a stable way to transport them around the country, but it is not intended to be a long-term home for the plants.  That kind of plastic pot is much too narrow for a plant like the water lily, whose roots spread out horizontally like a carpet.  They can still survive in such a container, but their growth will become stunted, limiting the number of flowers the plant will produce.  

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When you purchase your lilies from a specialty retailer like Landvista Aquascapes, they will come already repotted, fertilized, and ready to add to your pond.  It can be easy to underestimate the value of getting mature plants that have been professionally tended, fertilized and potted.  
For the best results, we recommend potting your lily in the largest pot possible.  We like to use the fabric lily pots from Aquascape that are 7" tall and 14" in diameter.  They have a cinch top that is useful for containing the soil, and the flexible shape works well to conform to uneven rocks at the bottom of the pond.  

Start by adding about 3"-4" of specially-formulated planting media to the fabric pot.  Once that is done, it's the perfect time to add some fertilizer.  We use two types: quick-release tablets and once-a-year pellets.  This provides the plants an immediate source of nutrients for establishing itself in its new home, and a sustained source of nutrients that will keep it well-nourished throughout the year.  After adding the fertilizer, we like to cover it up with a little more soil; another 1/2" to 1" will suffice to protect the plant roots from direct contact with the fertilizer and encourage root growth.  
 

Floating plants can spread over the surface of a pond, as seen here with some prolific water lettuce.

If you are planting marginals, remove the plastic pot and gently loosen the clump of roots and soil before placing the plant directly on top of the fertilized soil already in the fabric pot.  This will help the plant adapt to its new pot and allow the roots to expand, giving the plant a stronger start for its new life in your pond.  If you are placing more than one plant in the pot, leave some space between them to allow the plants to fill in as they grow.  

​A nice trick when potting marginals is to place a smaller plant towards the edge of the pot with the taller plant in the center.  This creates a cascading effect and will soften the edges of the pot, better blending it in with the rest of your water garden.  
If you are planting a hardy lily, place the tuber at the edge of the pot, angled towards the center with the spiky, growing end pointing upwards.  

At this point you can add spread small rocks or pea-gravel atop the soil in the pot to protect the soil from fish and help contain it within the pot.  
Now you are ready to place the freshly potted plant in the pond.  Gently lower the pot into the water at a slight angle, so the rush of water doesn't displace a bunch of soil and cloud the pond.  The optimal depth in which to place your potted water lilies is 10" to 18".  Too shallow and the stems will stick out of the water, attracting aphids that the fish would otherwise eat and keep under control.  Too deep, and the pads will struggle to reach the surface, nor will you see many flowers.  Don't worry if the lily pads do not reach the surface at first, they will quickly grow towards the light. 

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If your pond is very deep all over and lacks a shallow shelf, you can use rocks to raise the height of the lily pot.  This technique is also useful when you have just planted young lilies or potted a new lily tuber.  The young lily does best when it isn't too far from the surface, so a stack of rocks that will lift the pot and bring the growing tip of the plant within a foot of the surface is ideal as the plant is getting established.  As it grows and sends out leaves, you can remove rocks from the stack so the pads rest on the surface without sprawling out.  A useful alternative to a stack of rocks is to use an upside-down clay pot with a piece of flagstone placed on top.  The terra cotta clay will eventually get a coating of algae and blend in with the rest of the pond.  An added bonus is that if the clay pot is large enough, you will be able to cut an opening on the side and transform the pot into a functional fish cave!  

Another option for deep ponds (5' or greater) is a relative of the Nymphaea genus of lilies that is found growing wild here in NJ; it is known as Nuphar Advena, aka Spatterdock.  This plant is very similar to the hardy and exotic lilies that are kept in backyard ponds, but it has two main differences:  leaves that are pointed at the tip and often rise a few inches above the water, and its spherical yellow flowers that smell like grape brandy.  This plant is a vigorous grower, and it will expand to cover as much of the pond as you allow, so annual thinning may be required to keep it under control.  In natural ponds, turtles and beavers will eat all parts of it, maintaining balance in the ecosystem and preventing the plant from taking over.  

For marginal plants, the optimal depth is where the edge of the pot comes just below the surface of the pond.  Marginals should go on the outer shelf of the pond, or at about 12" deep.  
Floating plants are simply placed in the water wherever you'd like them.  They require no potting, as their roots take in nutrients directly from the water.  These plants are fun and easy to keep, and can be a nice food source for fish, turtles, and birds.  They grow so well that they may need to be thinned out occasionally.  Just be careful in case you happen to have one of the few invasive species of floating plants that is banned in NJ: Eurasian water milfoil, hydrilla, and water chestnut.  If you do have one of those species, they must be destroyed when they are removed to prevent the potential spread to natural waterways.  ​

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Adding plants to your pond not only supports biological filtration, it also helps shade fish from predators, adds color and depth to your pond, and comprises one of the essential elements in a balanced aquatic ecosystem.  Watching the flowers on a water lily bloom in the daytime and close in the evening is a simple joy that connects you to the natural rhythms of the planet.  

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