In this post I’ll look at some specific plants and discuss ways to overwinter them. Some plants can be brought indoors and grown in a green state just like your other house plants. Others can be easily stored in a semi-dry dormant state.
In my post, Overwintering Pond Plants – Part 1, I reviewed general ways to overwinter both hardy and non-hardy plants.
The umbrella palm (Cyperus alternifolius) is a tropical plant that is hardy to zone 7 and by fall it can be 6 feet tall. Smaller palms such as the dwarf umbrella palm are also available and can be treated in the same way.
These palms can be easily grown indoors near a sunny window and then taken back out in spring. Keep them quite wet and consider growing them in a pot with no holes so that they sit in water all of the time. Give them as much light as possible.
These plants are difficult to store in a dormant state.
The tubers of canna lily plants are quite tough and can take some light frost. Leave the plants outside until you have the first good frost. Then dig them up and cut off the roots, leaves and stems. You can divide larger bulbs by braking them into smaller pieces. Leave them exposed for a few days to dry out.
The key to storing them is to keep them cool, dark, not too dry and not too wet. If they are too wet, mold grows on them. If they are too dry, they shrivel up and die. Don’t let them freeze.
There are many recipes for getting this just right and the best one depends on your storage conditions. Many people pack the tubers in slightly moist peat moss and leave them. Wood shavings, saw dust, coir and vermiculite are also used. To be honest, when I use peat moss, they tend to dry out too much.
You can also pot them up right away, in a soil-less mix and store them that way. This helps keep moisture around the roots and they are ready to grow in spring, but they do take up more space this way.
Check them once a month. If mold is growing on them, dry them out more. If they start to shrivel , they need more moisture.
In early spring, warm them up and after a couple of weeks, water them very sparingly until you see new growth. Remember that the new leaves get water from the tuber and they don’t need much watering until they have a decent sized root mass. Soil that is too wet can rot the roots.
This is rated as a zone 6 plant. One way to overwinter it in zone 5 is to sink it to the bottom of the pond where it will stay warm enough. I tried that once and the plant did not make it, but it should work.
Thalia does make good sized tubers and you should be able to store them inside similar to cannas, but this does not seem to be the commonly recommended practice.
Elephant ears produce large corms that overwinter easily in a cool spot. Just remove roots and foliage in fall and store dry. Here is a video that will show you exactly how to do this.
If the above video does not play, try this link: https://youtu.be/NPBrZs9Q2CU
Tropical Water Lilies
Hardy water lilies can just be left where they are. If your zone is too cold for them, grow in pots and lower the pots to the bottom of the pond for winter.
Tropical water lilies need to be kept at a minimum of 45ºF (7C). The best way to do this is to remove the plant from the pond in fall, and cut off all leaves and flowers. You will be left with round tubers the size of a golf ball or even smaller. Pack these in a glass jar along with some damp peat moss and store at 45 to 50ºF (7-10C) for the winter. Take out the tubers in spring and warm them up so that they start to grow. Return them to the pond once the temperature stays above 70ºF (21C).
You can find out more about water lilies here: Water Lilies: Hardy and Tropical Water Lilies for Ponds
Water Lettuce and Water Hyacinth
Most people discard these plants in fall and buy new ones in spring, due to the low cost of the plants and the effort needed to overwinter them. Add them to your compost pile.
If you do want to overwinter them you will need an aquarium or shallow plastic tub and some fairly strong light. They don’t like moving water, so turn any filtration off. They should do fine until spring. If the water is fresh tap water, add a very small amount of fertilizer to get them started. This method works better for water lettuce than for water hyacinth.
Another method you can try for water hyacinth is to plant them in sand or soil that is kept very wet – basically a wet bog condition. Give them lots of light.