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Overwintering Pond Plants

Last Updated: 11/18/13

Overwintering Hardy Marginals and Iris
Overwintering Tropical Marginals
Overwintering Submerged Plants
Overwintering Lotus
Overwintering Hardy Waterlilies
Overwintering Tropical Waterlilies
Overwintering Hardy Floating Plants
Overwintering Tropical Floating Plants

For more on each of these plants, see the pond plant index for links to pages on those plants.

For more on winterizing a pond, see my winterizing page.

Overwintering Hardy Marginals and Iris

Cut all of the dying vegetation as it yellows/browns about an inch or so from the top of the pot. Move remaining pots deeper into the pond if needed so that the plants' roots will not freeze. My pond is large enough so that in Zone 6/7, the marginal area only freezes down a few inches which is not far enough to harm the roots. So, in my case, I do not move the pots deeper. If the pond is too shallow or you do not intend to keep an open area in the ice, you can overwinter hardy plants inside too.

In the fall, I remove yellow and brown vegetation weekly and at some point (after the first frost), cut back whatever remains of the hardy marginals and iris. The iris are the last to be cut as they stay green past the frost.

Most hardy plants can remain in the pond as long as they will not freeze solid. After the leaves have yellowed and been cut off, the pots should be placed so that the roots of the plant will not freeze. In my pond, I can leave them where they are as the ice stays above the pot rim. Each pond is different. In colder areas, the pots may all need to be lowered down deeper or brought inside. Some plants can take their roots freezing including common cattail. To overwinter most hardy plants inside, they can be put in a refrigerator or cold room and kept moist but in the dark. Tuberous plants (hardy water lilies, hardy canna, lotus, etc.) can be partially dried and kept in moist sand. If conditions are not proper, the plants will turn to mush. As I have not overwintered hardy plants indoors, I do not know the details. It is usually easier to overwinter outside. Only if the pond will freeze solid (tub ponds) must hardy plants come inside. Some hardy pond plants (cardinal flower, lizard tail, iris, etc.) can be overwintered buried on land if they cannot stay in the pond. In the case of cardinal flower, it usually dies if overwintered in the pond but not if overwintered on land.

Overwintering Tropical Marginals

In areas where it goes below freezing, tropical marginals will not be able to stay out in the pond over winter and survive. Tropical marginals can be overwintered in a sunny window or under grow lights as long as they are kept wet over the roots. A small indoor pond works well for taro, papyrus, hibiscus, and others. Tuberous tropical plants like tropical water lilies, taro, and canna can be overwintered alive under intense lights (sunlight, full spectrum fluorescents, or better yet metal halides) or with just the tubers stored in a cool area in damp sand. I have found that taro and canna prefer to remain active over winter and not dry stored. If dry stored, the tubers are susceptible to fungus. Canna can be overwintered in damp sphagnum moss.

Overwintering Submerged Plants

Submerged plants do not need to be cut back if alive. Any parts that freeze solid over winter will probably turn to mush so it may be wise to sink submerged plants that are close to the surface. Submerged plants (tropical or hardy) can also be overwintered indoors in a small pond or aquarium with full spectrum lighting.

Overwintering Lotus

Lotus can be treated as hardy marginals. Any tubers that freeze solid will probably die. Rotting lotus tubers turn mushy, black, and/or stinky. Healthy tubers are yellow and stiff. Lotus kept in tubs that will freeze should be repotted into something and sunk into a deeper pond. Or, new ones can be bought each year. Or, tubers can be overwintered indoors at about 40-50 degrees F in a fashion similar to tropical water lilies (details below). I have not tried overwintering lotus indoors so I do not know how well it works.

Deb shared her story of overwintering lotus tubers indoors in my January 2006 pond newsletter under pond tidbits.

Overwintering Hardy Water Lilies

Hardy water lilies should have their dying leaves removed and be lowered such that the roots will not freeze over winter. I leave mine in place but in some ponds, the pots may need to be lowered. Do not feed water lilies once the plant starts to die back for winter (you remove more yellowing leaves than the plant puts out). In Zone 6/7 of the US, this means about mid- September.

Overwintering Tropical Water Lilies

Pond literature includes a number of different ways to overwinter tropical lilies so that they can be enjoyed year after year in temperate regions. In the fall, tropical lilies should be removed from the pond in areas that become cold. All leaves and roots should be cut off. The tubers should be hosed off and all debris and dirt removed. They should be left to dry for a day or two in a dark area before storing (although I usually ski that step). Here are some of the various methods that I have encountered for storage:

This all sounds simple but that is not always the case. Through my own experiences and what I have read from others, lily tubers will suffer from these main problems when stored: fungal infection, too cold a temperature, lack of air circulation, and more. Fungal infections can be somewhat prevented by sprinkling the tubers with something called Banrot which I have yet to find sold anywhere. Instead, I try to prevent fungus by not storing the tubers too wet and by checking them often and changing sand if needed. I also use plant or lizard sand (that is sand sold for desert reptiles) in small bags (expensive) instead of builder's or play sand as these sands usually are more sterile. Tubers may die in a refrigerator if they get too cold. I think one key to keeping tubers alive is not to seal them into a container or ziploc bag. They need to breathe. What follows are my experiences and how I finally managed to overwinter a tropical lily.

I had bought four tropical lilies (up to 1999, more since then) since I started with ponds that I can think of right now. One died right away (in a tub pond with mosquito fish that I think ate it!). One was a blue capensis in 1999 with gorgeous blue flowers. This was the first that I tried to overwinter. I stored it in sand in a ziploc bag in the door of the refrigerator. I checked it a few times to be sure it stayed damp. Within a few months, all that was left was a pile of mush. That method did not work for me. I think it was too cold, and the tuber did not get the air circulation that I mentioned.

In 2000, I bought an unknown variety of pink night-blooming lily. It has huge, dark green leaves with spikes around the edge. The flowers open as white, well above the water, and change to a pink and white over the next few nights. Flowers open at sunset and stay open a few hours after sunrise. This time, I tried a totally different method to store the tuber over winter 2000-2001. I cleaned and dried the tuber. I put it in a ziploc bag with lizard sand (which is more sterile than regular sands) and added enough water to make it clump up. I put the ziploc into a Lerio pot (all black) in the basement (about 55-60 degrees in the winter), left the ziploc OPEN, and put a paper towel over the top to block out light. I put the whole thing in a dark corner of the basement. I checked the dampness weekly but only added some water every three weeks or so as it stayed pretty damp. After about a month, the large tuber appeared to turn to mush. I was going to toss it out but I took it to the laundry tub and washed through it. It turned out that there were two acorn-sized clumps left in the center. Those must be the true tubers that I was supposed to store, not the entire, banana-shaped tuber. I did not know if these were viable but put fresh, damp sand with them and back into the same setup. In late April, the tubers seemed to be showing signs of sprouting. So, I put them in a 5 gallon pot in my 1800 gallon pond. After a few weeks in the too-cool water, it appeared dead. I had thought I had failed again (by putting it out too soon). In June, I bought a Director Moore blue day-blooming tropical lily and put it in the same pot that the "dead" pink night-bloomer was in. Well, when the tropical lily bloomed on 7/17/01, it was white and opened at night! That means that the pink night-bloomer did survive overwintering, and the blue day-bloomer died! So, I must have done something right for the pink night-bloomer! Success when you least expect it is quite perplexing. I had been planning to try keeping my new tropical lily alive in an indoor pond under lighting but now think I will stick with what worked last time.

For 2001 into 2002, I tried the above again with the same lily. For more information, see my November 2001 pond newsletter. On 5/12/02, I put the tropical lily tubers back into a 5 gallon pot into the 1800 gallon pond. Two of the four nut-like tubers had sprouts so it looked like the overwintering was a success for the same plant over two winters! It took about two months for the outer part of the tuber to totally rot off and allow me to remove the hard inner nut things. Because the outer part rots and stinks, I had to change the sand three times over winter. The last time, all that was left was the hard inner nuts which only rot if they die. By 8/28/02, this one tropical lily of mine is again king of the pond. The koi kept dislodging the tubers in May and June and some vanished but one managed to survive barely. By July, it really started to grow. It sent out leaves some 7 feet from the pot and had about two or three flowers every night that stayed open at dawn when I could see them. Here is a photo of one of the flowers taken 8/1/02 to enjoy!

I overwintered two of the nut-like tubers successfully again over the 2002-2003 winter in damp sand in an open ziploc bag in the dark, in the basement. We had a cold and wet spring, and the tropical lily got off to a slow start. It was alive but as of 8/21/03, it had not flowered this year when the previous two years, it had tons of flowers. I hope it will make it through its fourth winter inside!

I removed the tubers on 11/9/03 (see my newsletter from that time for more information). I got three of them but cut one. Here is a photo of the tubers so you can see what they look like! They are like nuts to me! The tubers were put back into a 5 gallon pot in my 1800 gallon pond on 5/23/04. I hope they grow!

The tropical lily did indeed do well the summer of 2004. I removed the two nut tubers in November for storage for the winter. See my December 2004 newsletter for more information. As of 3/6/06 (I guess I skipped a note in 2005), the same tubers are in the basement in damp sand waiting for spring. They almost died the summer of 2005 for various reason (cold, dog attacked the pond, etc.) but recovered enough to yield two tubers. My newsletters have details.

On 5/10/06, I put the three tubers (how did I gain one?) in a 5 gallon pot. It had been warm and then got cold so I hope they make it! They have no minute sprouts on them this year.

On 11/5/06, I pulled out the tropical waterlily after a frost and using my hands in the muddy roots, I found three tubers to overwinter. The lily did pretty well in the fall but it took it a few months to really get growing. On 1/20/07, I found the sand was too damp in which the tubers were overwintering. When I moved the sand, it stunk. So, I changed the sand completely. I think one of the tubers has a crack in it and might be compromised but I put it back anyway.

I put more little tubers back into the pond that spring as I had for years. They never grew any leaves. In the fall, I found one of the tubers. It was still hard so I put it in some sand but I think it is gone. After seven years, the saga of my pinkish white tropical waterlily is over. I will miss that gorgeous plant. The tropical waterlilies I have bought since do not produce the hard tubers so I have failed to overwinter any of them. Does anyone know what varieties produce the nut tubers?

I put the one little nut tuber in a pot in the late spring of 2008. It never did anything. It is truly gone. I found the nut that fall and overwintered it again and planted it again in 2009. Still, nothing. I miss it!

When I pulled out my new tropical waterlily from the pond on 11/15/09, I found that it had two little nut tubers which I put in damp sand. Perhaps they will make it! I also saved the growing part and put that in my basement pond. Here is a photo of them.
Waterlily storage tubers and growing tip

On 5/5/10, I potted up the tropical waterlily (Blue Beauty that I bought last year) in to a five gallon pot. This included the growing tip which was amazingly alive and doing well growing bareroot in the basement pond as well as the two nut tubers I had stored in damp sand all winter. Both of those also had little leaves on them! So, the overwintering of that waterlily was successful and hopefully they will stay alive now that they are in the pond.

I pulled out the tropical waterlily for the winter on 11/14/10. I found one main growing tip and two tiny ones and just one storage tuber nut thing. I potted up the three plants in a one gallon pot and put those in the basement pond for the winter. The tuber went in a ziploc bag with wet sand for winter storage.

On 5/4/11, I put the one gallon pot of tropical waterlily back in the 1800 gallon pond as is. If it grows, I may repot and move it. I put the one tuber in to the five gallon pot (without changing the dirt in it). Both versions of the waterlily overwintered well. The tuber had sprouted.

On 5/3/12, I potted up the one gallon pot of the growing tip as well as five hard nut tubers in to a single five gallon pot and put them in the big pond. I think the tubers were dead but the growing tip was alive.

On 11/5/12, I pulled up the tropical waterlily pot. I found seven nut tubers. Three were alive with growth. Four looked dormant or dead, and one of those fell apart when I put them in the Reptisand for storage. Dead waterlily nuts stink very badly when they break open! I did not keep any of the tubers active in a pot in the basement pond this time.

On 5/25/13, I potted up five nut tubers in to a 5 gallon pot in the big pond. Four of them were actively growing. I do not know what happened to the other two; they must have rotted.

On 11/17/13, I pulled up the tropical waterlily pot. I had intended to put the lily in a two gallon pot in the 20 gallon basement pond but I found all the leaves attached to nice, hard tubers with few roots. I found four nut tubers which I put in damp sand.

Overwintering Hardy Floating Plants

Hardy floating plants like duckweed naturally sink down in the water as it gets colder and then "magically" reappear in the spring. No special care is needed. Some floating plants will rot and die (the tropicals do since it is too cold but some hardy plants may as well) but a few hardy floaters manage to sink and come back.

Overwintering Tropical Floating Plants

Floating tropical marginals like water hyacinth, water lettuce, and salvinia can be overwintered if they have bright natural sunlight or intense artificial light (multiple fluorescent grow lights or metal halides). Water hyacinth seems to like a thin layer of soil in the bottom of its indoor "pond." Liquid fertilizer should be added as needed to keep the floating plants healthy. I have never successfully overwintered these tropical floating plants. They all turn to mush after a few weeks. The lighting has not been strong enough. Some people say that a heated greenhouse is absolutely required to overwinter water hyacinth. I have overwintered salvinia and frogbit in my aquariums under intense fluorescent lights.


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