Caring for Pond Plants

  Marginal Plants

    Marginal plants are water plants that grow with their roots below the water and their crowns slightly submerged, leaving most of the foliage out of the water.  Most marginals do best with the water 1-3 inches above the top of the pot.  Flowering varieties perform best in full sun, although most will grow fine in light shade. 
 
Newly purchased marginals may need to be repotted in a little as a month, especially ones purchased in 4 1/2” pots.  Plants purchased in one gallon and larger pots should be fine for the season.  Standard potting soil should not be used, as perlite and peat moss may float out of the pot once it is submerged.  Instead, heavy clay soil collected from the yard actually makes a better growing medium.  Avoid the upper 6”, as it may be too rich and foul the pond.  Line any drainage holes of the planting container with newspaper or burlap to keep the soil in the pot.  Make sure that if you use newspaper that it is printed with soy ink.  Place the plant in the container leaving the crown at the existing level and pack it tight.  Pea gravel on top of the soil will also help keep the soil from floating out.  Mineral potting soil is available and is a bit less messy.  Feed your marginals once a month with an aquatic plant food tablet for best results.  If a lot of fish are present in your pond, you might not have to feed your plants.

  In the fall after a good hard freeze or two, hardy marginals should be sheared back to remove all brown foliage but left where they are.  Half-Hardy marginals should also be sheared back and be over wintered below the freeze line, usually 6-8” below the surface, to avoid freezing out their crowns.  In mid-April, they should be returned to their original growing positions.  Tropical plants should be tossed before they freeze so they don’t pollute the water.  Some potted tropicals, like taro and papyrus, can successfully be over wintered as houseplants, kept in a shallow pan of water. 

 Water Lilies and Lotus
  Water lilies and lotus need at least 6 hours of sun to bloom their best, although there are a few exceptions, such as hardy lily ‘Chromatella’ and the blue tropical water lily.  Pots should be placed so that the crowns are 8-24” below the surface, although a few larger varieties can grow in water to 36” deep.  Waterlilies and lotus resent splashing water on the leaves, so avoid placing near fountains or waterfalls.  Make sure that at no point in the summer oxygenators or surface floating plants block the light reaching the crown, as this will reduce flowering.  Each leaf on a waterlily lasts only about one month during the summer, so removal of yellowing leaves down to the crown may keep them looking their best.  Old flower stems may be removed in the same manner, thus helping both lilies and lotus to rebloom.
 
  Waterlilies will be fine in the same pot for a while.  It may be time to repot when most of the rhizome has “jumped” out of the pot.  Repot in the same manner as described with the marginals, making sure to leave the crown above the soil line.  Removal of small offshoots will help the main crown produce more flowers. 

  Lotus need repotting every one or two years.  They may be uplifted from their pots in early spring while they are still dormant.  Find a healthy tuber with at least two internodes and a growth tip.  Pack clay soil tightly in the same or larger pot as described above, burying the tuber so the growth tips are barely buried.  The other tubers can be repotted or given away.  Feed waterlilies and lotus once a month with an aquatic plant fertilizer tablet, and twice a month may be necessary when the water temperature is over 75 degrees Fahrenheit.

  When winter comes, remove the foliage of lotus and hardy waterlilies and just make sure they are at a level where water won’t freeze down to their crown.  Tropical waterlilies should be taken from their pots for the winter and have all their dangling roots and leaves removed.  The rhizome should then be washed off then wrapped in slightly moist peat moss or damp newspaper and be placed in a plastic bag.  The bag should then be placed in a dark area of about 35-55 degrees.  A refrigerator or a root cellar would be fine.


  Submerged Aquatics (Oxygenators)

  Marestail simply require to be thrown into the pool.  Attaching a rock tucked in a rubber band will keep them submerged if desired.  Several may also be potted together in a shallow pan with gravel or sand in the pan.  When late fall comes, it is best to cut off the top several inches of the stems and bunch them together, weighing them to over winter on the bottom to avoid getting frozen.