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Dividing and Sharing
Aquatic Plants

by Rich Sacher, Louisiana USA
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Standard horticultural practice recommends that when a plant has outgrown its pot, it should be transplanted to a bigger pot. We can certainly do this with our aquatic plants if we have a very large pond and have the room for specimen plants. However, this can result in pots which are too heavy, or plants which grow too large.

Aquatic plants, like their terrestrial cousins, often need to be thinned out or divided. Some plants develop a clump which is too large for their pot, or for their location in the pond. Floating plants may become too numerous for the water surface. A hardy waterlily or a tropical night blooming lily starts the season as a single plant, and later becomes a crowded clan of competing siblings. Rather than transplant these plants to larger pots, most pond keepers prefer to divide their plants, keeping them in scale for the size of their pot and pond. We replant the biggest and best of what we have divided, which leaves lots of smaller plants left over.

Plant lovers are often reluctant to throw away perfectly good plants, even if they do not have room for them! These left over plants provide the opportunity for plant swapping with other pond keepers, an excellent way to acquire aquatic plants which we have not grown before. Here are some factors to consider if you decide to do some plant dividing and swapping.

HOW AND WHEN TO DIVIDE

Aquatic plants should not be divided in the fall, since they would be susceptible to root rot as they lie dormant in cold water through the winter. Spring is the best time for dividing aquatic plants. The plants are just beginning to start growth, and quickly recover from being divided. They can be repotted into fresh soil for the upcoming season, and you can use their previous year’s performance to decide on the number of plants you want and their placement in the pond. We should note here that many aquatic plants can also be divided in the middle of the growing season if they have become so large that division is desirable.


Lotus are an exception to mid-season division, since they do not recover easily if their roots are disturbed once they are in active growth. They can be carefully moved to a larger pot during the growing season if necessary, but they should not be divided except in early spring, while the plant is dormant. Lotus tubers are the size and shape of bananas, and always end up on the very bottom of the pot. The easiest way to find them is to turn the pot upside down and use a hose to blast all the soil away. Each tuber must have a growing point in order to survive. These growing points are very fragile, and must not be damaged in the division process. I treat these growing tips as if they were made of glass. You can cut the runners between tubers, but do not cut the tubers themselves.

The tubers can be replanted in fresh soil, usually 2-4 tubers per 16-24 inch (41-61 cm) pot. Left over tubers can be stored in damp peat moss in plastic bags. The peat moss cushions the tubers, and its acidity prevents molds and bacteria from attacking the tubers. Keep them in the refrigerator, (NOT the freezer!) until you are ready to exchange them for other plants. A frost free, cool basement or garage works fine for cold storage, too. A waterproof name tag in each bag will prevent confusion when you bring the bagged tubers to the plant swap. This same storage method can be used for a number of semi-dormant aquatic plants: Canna, horsetail, cattail, etc. can be held dormant for a month or so this way. Although lotus require long, hot, sunny summers in order to bloom well, they are quite hardy as long as the soil they are growing in does not freeze in the winter.


When dividing plants, it is always worthwhile to keep as many functioning roots as possible on each division. As soon as a section of plant has been divided, put the roots in water so they cannot dry out. Once you have replanted the best divisions for your pond, you need to decide what to do with the left over plants. They can be placed in tubs of pond water in a sunny location, with a pinch of fertilizer added to the water. They can be held indefinitely this way. Bare root plants are easier to take to a plant swap, and the small amount of fertilizer in the water will allow the roots and tops to grow while you are waiting to have a plant exchange. Or, if you have the inclination and the space, these divisions can be planted into pots of soil, and grown for a while before using them for trade. In a case like this, I like to use the smallest pot which will accommodate the root system without crowding it, knowing that the new owner will transplant it to a larger pot before putting the plant in its new home. 

 

The method of division depends on the growth pattern of the plant. Overgrown plants, such as cattails, papyrus, horsetail, bulrushes, etc., have many individual plants in the pot, and we can divide them into two to four clumps. These types of plants are usually divided by using a knife or even a small saw to cut the root mass into the desired number of clumps.

Sometimes it is feasible to cut the root mass half way down, and then pull the divisions apart, thus preserving more root system for each clump. (If you pull the roots apart under water, you will break fewer roots!) The best divisions can then be replanted for your pond, and the left over plants can be kept bare root in water, or planted into small pots for later plant swaps.

Plants with rhizomes, such as hardy waterlilies, water Iris, Acorus, Canna, etc., should have the old soil rinsed from the root mass to reveal the joints in the rhizomes. This makes it easy to see where to divide the rhizomes. Each division should have a minimum of 3-4 inches (8-10 cm) of rhizome, with the growing point and roots attached. If you are using a 14-16 inch (36-41 cm) pot for these plants, you may want to replant three or four rhizomes in one pot, to create a fuller plant more quickly.

 
 

Plants which make tubers, such as night blooming lilies, water hawthorn, Chinese water chestnut, etc., should have old soil rinsed off their root mass so the individual tubers can be seen; cut or twist the tubers from the root mass. There may be 10-15 tubers in an overgrown ten inch pot; night blooming lilies are usually planted one to a pot, since they are so prolific in making tubers during the season. Water chestnuts, hawthorn and taro may be planted with 3-4 tubers per pot, to more quickly create a full plant for the summer season. The left over tubers can be planted into 4-6 inch (10-15 cm) pots for later plant swaps or, they can be held for a few weeks in pond water; they can also be stored in damp peat moss, at 40-55 degrees F (4.5-13 C).

Tropical waterlilies also make tubers, but often they are large, soft tubers which do not usually survive the winter … even in a greenhouse. However, sometimes there will be several small, hard tubers attached to the large tuber, and these small tubers (½-2 inches [1-5 cm] in diameter) can be removed and planted into individual pots. They will not usually begin growth until water temperature is above 70 degrees F (21 C), so if an indoor pond is available, they are best started indoors and moved outside later. Surplus tubers can be placed in zip-lock plastic bags of water and held at 60-70 degrees F (15.5-21 C). Some of them may sprout and develop a few small leaves, but they will not begin full growth until placed in a warm, sunny pond.  


Some tropical waterlilies are viviparous … during the summer, they make new plants in the center of their older leaves. These plantlets will develop roots while still attached to their leaves, and sometimes they will produce flowers too. These are easy waterlilies to propagate, and they are the origin for many of the tropical waterlilies which hobbyists use for plant swapping. These small plantlets can be removed from the fading lily pad and planted into 4 inch pots of fertilized soil. Place them in shallow water (3-4 inches [8-10 cm] over the pot) in a warm, sunny pond. They will develop into blooming plants in 3-5 weeks.

Not every viviparous cutting will be successful, so I like to put two or three of them in one pot. If all of them root, they can be separated after they have produced their second or third flower. Soil is rinsed from the root mass and the plants are gently pulled apart under water, to minimize any root loss. You can then repot the lilies, one to a pot; or, if the plant swap is within a few days, you can let the plants float in the pond until you take them to the swap.

Plants with floating leaves, whether bare root or potted, should always be kept in sealed plastic bags to prevent them from drying out. Keep the bag out of direct sunlight, so they will not become overheated. Waterlilies, water clover, parrot’s feather, snowflake, water poppy, etc. can all be transported safely this way.

For delicate plants, you can divide them at the crown, and then tease their roots apart. For a tough plant like umbrella palm, you may need to saw through the entire root mass ... including the pot!

 


ARRANGING THE PLANT SWAP

The easiest way to find other pond keepers who are interested in exchanging plants is to join a local pond society. Most have monthly meetings during the growing season, and many groups have newsletters which facilitate plant sharing among members. Some clubs designate a particular meeting each spring especially for plant sharing. In some cases, members donate their excess plants to the group to be used as a fund raiser, and members get first chance to buy these plants at reduced prices. Other pond societies ask their members to donate their extra plants to a local botanic garden, to be included in the annual plant sale which supports the garden. (Show up early, and you might be surprised at the variety of plants which are offered for sale.)

Local newspapers often have a plant section in their “For Sale” classified ads, and this is another way to offer to sell or swap your extra plants. It is also a great opportunity to meet other pond keepers in your area.

Neighborhood newsletters are another possibility for advertising your aquatic plant swap. They cover a smaller geographical area than a regional newspaper, and this makes it easy for neighboring pond keepers to get together.

DO NO HARM … AND STAY OUT OF TROUBLE!

I do not suggest using the internet for plant swaps, since it can give rise to all kinds of problems. Remember, the internet is a world wide medium. What will you do when you get email from someone in Kuala Lumpur, offering to send you his exotic aquatic in exchange for your extra waterlily? Is it legal? Do you need a permit? Will the plant survive shipment? How will it be packaged, and what will it cost for postage? Shipping plants into other states or countries is best left to professional exporters and importers … otherwise, you can get into trouble. The list of banned plants varies greatly from one place to another. Without realizing it, you could be guilty of importing or exporting a noxious weed that eventually could cost millions of dollars to eradicate or control. We only have to think about the lovely water hyacinth which now clogs our southern waterways, and we get an idea of how destructive imported plants can become.

The next scourge of lakes and bayous in the south may be the giant Salvinia, an escapee from South America. This free floating aquatic can form an impenetrable mattress a foot thick, killing all aquatic life beneath it, and has already invaded waterways in Texas and Louisiana. It was most likely brought into the country by an aquarium keeper, and it is now being spread from place to place by boaters as they move around to various recreational waterways.

Even mailing plants to an adjoining state has its problems: they may be delayed in the mail, and the recipient may want you to replace it if it arrives dead or in poor condition. Or, the plant may not be the size or variety that was expected, and this can cause disagreements. It may even be listed as a forbidden noxious weed in your neighboring state!

When plant swaps are done in person, everyone can see the plants being exchanged and ask questions about their culture. The plants can be carefully examined for evidence of insect infestation. This exchange of information can lead to engaging conversations that benefit both parties.

It is helpful to know that the plants being swapped have come from another hobbyist’s pond, and are not plants recently collected from the wild. Wild-collected plants can bring with them weeds, insects, fish parasites, snails, crayfish, etc. that you do not want in your pond. Free floating aquatics like water cabbage or water hyacinth may have insects, crustaceans or fish eggs concealed in their root system. Even plants from a fellow hobbyist’s pond may harbor an undesirable critter. I once took home a potted bog plant that had a pigmy rattlesnake hidden among its roots!

Which brings us to this recommendation: you may want to quarantine any new plants that you acquire, whether by purchase or plant swap. New plants can be held in a separate container of pond water for a week or two, while daily observations are made for any unwanted hitchhikers. It is a common practice to quarantine new fish before they are introduced to the pond, and so it makes sense to follow this same procedure with plants as well.

Plant swapping is a great way to try your hand at new aquatics. You get to acquire new plants, expand your knowledge, make new friends … all because of your plant exchanges! Who would have thought that “leftovers” could provide such a welcome addition to our menu of pond plants?

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