Winterizing Tropical Waterlilies
With Tips for the Rest of the Year
by Bob Meyer, Tolono, Illinois, Borderline
Click images to enlarge
I have done this for the last 5 years and have about an 80% success
rate. I am currently overwintering about 20 tropicals that will
eventually be started in a 10 gallon aquarium in the spring.
First of all, I live in central Illinois, zone 5/6 borderline.
Tropicals should not be put out into a pond until the water temp
is 70 degrees. Waiting till 75 would give better results. Keep
in mind that your daytime air temps may be 80 and your pond temp
still 60. Many tropicals do not form a tuber if they are pampered
during the year. Big pots with good soil and lots of fertilizer
result in beautiful flowers, but you may or may not get a tuber.
To force a tuber, the plant has to be stressed. Forming a tuber
is the tropical waterlily's way of surviving if the conditions
are bad. Keep your plant potbound in a quart sized pot or smaller,
stop fertilizing and lift the pot up in the water so that the
crown of the plant is at the water level. The crown is where
the root meets the leaves. If you do this, the plant will often
form a tuber. The newer hybrids seem less willing to form a tuber
than the old standards.
About the time that your water temp gets into the 50s, check
your tropicals for tuber formation. You can do this by slipping
your finger into the soil just under the crown. If it has a tuber
forming, leave it alone. If you don't feel a tuber you may want
to try this last ditch effort! Pull the entire plant out, rinse
off the roots and check for tubers. If no tuber, just let the
plant float for the next couple of weeks. A floating tropical
sometimes forms a tuber.
When to pull:
Very little plant growth happens once the water temp drops below
50. Some people like to leave the plants out to get that last
ounce of growth and maybe an extra flower or two. But you also
risk a sudden storm coming in or family emergency coming up and
not being able to pull your tubers. I like to wait until the
water hyacinth, water lettuce and duckweed start to die. This
usually occurs after the first hard freeze. Here in Illinois,
that is at the beginning of October. Some years we have some
warm up weeks and tubers could be pulled throughout October and
November. Some tropical waterlilies will survive a layer of ice
forming over the pond, but will not survive having their tubers
frozen solid. I have seen tropicals in flower in a frozen over
pond. Albert Greenberg seems to be a tropical that fits into
this category. It just keeps going and going.
How to pull:
Bring out a 5 gallon bucket half filled with warm water. If you
have to work in water, might as well be warm! Lift the plant
out of the pot and rinse the roots in the 5 gallon bucket. If
a tropical is going to form a tuber, it is usually within a few
inches of the crown. 'Red Flare' and the various red night bloomers
seem to form a large tuber. The day blooming blues seem to form
several small ones. I have seen tubers the size of my fist and
as small as pea gravel. I put the tubers in ziplock bags and
label the bags while I am outside. Then you have a several options
with the parent plant. You can loan it to a friend in a warmer
climate to overwinter for you, you can repot it and hope for
more flowers, or you can float it and hope for a second tuber
to form. If your plant is viviparous (babies form on leaves),
this is a good time to pull a few leaves to keep inside or trade.
Bringing the pot in:
If you are in Zone 8 or 9, you may want to consider waiting until
the first freeze and then lifting the entire pot out of the pond,
clipping off the leaves and storing the entire pot inside. Let
them drip dry for a couple days, then put them in a garbage bag
and place in a cool place. Do not tie the bag shut or they will
surely develop fungus. Then when the water temp gets warm, you
can just drop the entire pot into the pond. This method takes
up a lot of room, it is hard to manage the moisture level, and
fungus/mice are problems. I would not recommend this method unless
the pot needs to be kept inside for less than a month. I have
poor success with this method, but my plants are out of the pond
for almost six months of the year. Some of my tropicals were
still very small and I brought the entire pot in and put the
pot into an aquarium. They survive for me, but don't do great.
Inside the house:
I take the tubers and rinse them in tap water. You want to get
the dirt and dead roots off of them. I then lay them on a paper
towel and let them air dry for an hour. Then I get a tupperware
type container. Various forms of these are sold near the garbage
bag section of your local grocery store. I think I buy the Glad
ones that are maybe 5 containers for $2. Half fill the containers
with sand. Add a little bit of tap water. Put the lid on, and
turn the container on its side. If you have the water level correct,
just a drop of water will flow out when it is on its side. The
sand should be damp, not wet. Now, you have the option of treating
your tropical with a fungicide. Captan works, sulphur works.
Wrapping the tuber in sphagnum moss may help too. I generally
don't use anything. Dig a little depression in the sand in the
container. Place the tuber in the sand. Lay a double layer of
paper towels over the tuber. Cover with a little bit of sand.
Then if you want to check on your tubers, you can just lift the
paper towel up to see the tubers. I place a label marker in the
sand with the name of the tropical and also label the container.
Where to store:
You want to store the tubers where the temp will be between 40
and 60 and will be dark. A refrigerator works. I just put mine
in the basement. Be careful that you don't put the tubers someplace
that mice can get to them. In the garage, a mouse will almost
always find them! Now just sit back and forget them!
About 8 weeks before you want to put the plants outside, you
can start them inside in an aquarium. I start mine in late February/early
March. Take a drinking cup and fill the bottom half with good
topsoil. Then add a layer of sand or pea gravel. Take your tuber
out of the tupperware container and place it so that about half
of the tuber is sitting out of the sand. When you have experience,
you will know where the growing point is and will be able to
plant it a little deeper. Then fill the cup with water and put
in a sunny hot place. 70F is a minimum, 80F is better. Eventually
the plant will have to go into an aquarium, so you may just want
to put the cup into an aquarium right away. I like to put the
cups on a heating pad for a week, and then put them into an aquarium.
The first few days after potting, the tubers frequently pop out
of the sand and float to the surface. In an aquarium, it is easy
to mix them up. But on a heating pad, the tuber stays in the
cup. Once a few leaves have formed, I move the cups to an aquarium
with lots of light. I have success with daylight and an overhead
bulb. The water needs to be kept warm, with 70 being a minimum
and 80 being the preferred temp.
Once the plant has about 3 to 4 quarter-sized leaves, you can
lift the tuber out of the pot and twist the plant off. Pot this
plant up in its own labeled cup and repot the parent tuber. About
a dozen baby plants can be formed with the first ones developing
maybe a week apart and the later ones taking longer and longer
to form. I have a 'Red Flare' tuber that I received 3 years ago
and it still forms baby plants. But the baby plants come about
6 months apart now! Once a tuber gets this drained, you really
should plant the tuber with its last baby outside where it can
store up energy again!
Once the tubers are in their own cups, I like to start fertilizing.
I use Jobe plant spikes or similar type lily tabs. I am putting
the starts in their own cups in the same aquarium as the tuber,
so I am sure that the fertilized water gets over to the tuber
After about 8 weeks in the aquarium, the plants can be moved
outside. I like to move the entire heated aquarium outside. I
have also had success moving the plants into a 'cone of water'
or tomato hotcap. These 'cones of water' are sold for tomato
plants. It is a cone that forms a mini-greenhouse inside and
stays about 20 degrees warmer than outside. You can put 2-3 small
starts in a gallon bowl in each cone of water. When you move
the plant from inside to outside, it is common for the plant
to lose half of its leaves. So don't move it outside too early.
Wait until it is good and healthy.
Repeating the cycle of life:
Hopefully you will have several starts of each of your plants.
Now is a good time to trade a few of these with others. Leave
a couple of the starts in the drinking cups and move the remainder
up to quart sized containers. The ones in the cups will be stressed
to form next year's tubers. The ones in the quart size containers
will grow and eventually need to be moved to gallon size containers.
I have accidentally left a few tubers outside and most freeze
and die. A very small percentage have actually survived here
in Illinois. That is with temps down to 0 and a pond that freezes
almost solid 12 inches deep. However, these tubers that survive
don't start sending up shoots until late in the next summer and
don't get big enough to bloom that year. 'Blue Beauty' seems
to be one of these freeze tolerant tropicals.
Don't give up on a tropical. I had a couple of tropicals that
stayed small and rarely bloomed for me one summer. When I pulled
the tubers, they were average size. But when I started the tuber
the next spring, I got lots of good plants. Sometimes the plants
that are doing the worst are storing up lots of energy for next
year. And the plant that did the best for me this year did not
form a single tuber. It had a 20 foot spread, a dozen flowers
every day and not a single tuber! I should have stressed that
plant more! White tropicals seem to be the easiest to overwinter
for me. Yellows are very very difficult.
Calendar: Zone 5 Illinois
Overwintering Tropical Waterlily Tubers
October and November, after first frost, pull tubers
December and January, enjoy the holidays
February and March, start the tubers in cups on a heating pad
April, twist off starts and pot them up inside
May, start moving tropicals outside to 'cones of water' and hotcaps
June, all the plants should be outside. Start fertilizing.
July, transplant up to bigger pots, fertilize biweekly.
August and September, make starts of viviparous tropicals.
October, move tropical pots to edge of pond to make access easier.
Place pots higher in water to encourage tuber formation.
by members of the Victoria-Adventure Email Discussion List
From Tuber - by Kit Knotts | Overwintering
Tropical Waterlilies - by Rich Sacher
Also see Sean Stevens' Tuber Propagation and Propagating
Ponds & Patio Garden / Tutorials