How to overwinter tropical water plants

Photo courtesy of Mary-Kate Mackey
Tropical water plants in party containers await winter banishment to the dark.

For those gardeners with water features, cooler days mean preparing to put the plants to bed for the winter. Many varieties, including hardy waterlilies, can stay where they are, but a lot of the most spectacular water plants, like cannas and  elephant ears, are tropicals and need protection.

I have successfully overwintered these by giving them a near-death experience. Around frost time, I lift the pots and provide leak-proof basins for them to sit in — either singly or smaller ones grouped together in one tub.

Over the years, I have made a collection of inexpensive plastic party buckets — now’s the best time to find them on sale — the kind that would hold ice or drinks. These absurdly cheerful containers provide winter homes for my tropicals as they sit in the darkness of my 40-degree F. (4 degrees C) garage.

I tag each plant with its name when I place it in the basin, and fill the bottom of the party buckets with only a few inches of water. I continue adding water to the basins to maintain an inch or so throughout the winter. The plants are not soaking wet, but never completely dry.

My garage came equipped with an indoor hose bib with hot and cold water — handy for plants or washing the dog — but I could also fill the containers using a watering can.

The darkness, cooler temperatures and lack of complete submersion sends the plants into dormancy. Their leaves go brown and they just sit there.

Tubers of night-blooming tropical waterlilies can be removed from their pots and stored in other pots filled with damp peat moss.

Well after the last frost of spring, I pull the basins out of the garage and place them in a sunny area. I fill the party buckets with fresh water and give each plant a spike of water plant food. If the roots seem very crowded, I repot with the heavy soil that these water plants prefer.

Then I watch for new growth. When I spot it, they go into their summer homes. Tropical water lilies are a bit fussier about the cold and shouldn’t return to their place until water temperatures hit 70 degrees F. (21 C).

Fragrant plants and water go together – a promise of relaxation and rejuvenation – so I also use this enforced dormancy for the highly scented tropicals I grow in containers that surround my water features.

I have several different kinds of brugmansias. Their dramatic trumpet flowers fill my evening garden with strong fragrance from August on to frost.

I grow another night-scented bloomer that I would never be without.

I first noticed its powerful presence in September 1972, when I moved to San Francisco. That night I stepped out the back door of my newly purchased home in Noe Valley, and the air smelled like Hawaii. I couldn’t get over the alluring perfume. By day, I peered into my neighbors’ yards, but nothing looked like it qualified for such flower power.

Each September the delicious scent returned, always a mystery. Years later I moved to LA, and my nose tracked down the scent. It was coming from insignificant looking white flowers— closed in the daytime— drooping at the tips of a six-foot-tall, rather weedy specimen growing neglected in a corner of a friend’s garden. It was night-blooming jasmine (Cestrum nocturnum). Eureka.

On the day frost is predicted, I trundle the large pots of tropical plants into the garage, where they remain all winter. I use my red hand truck — my friend Vanca Lumsden named her hand truck “Betty” for Betty Friedan, because it makes her feel equal to a man.

Mine remains unnamed, but it delivers the plants into the dark. At first they continue to bloom valiantly. Then shock sets in. They drop all their leaves and hunker down. I put saucers under each and keep the soil barely moist with occasional waterings until well after the last frost.

It’s no good bringing them out agin until the nights are reliably above 45 degrees F. (7 C) When they do emerge, I cut back everything obviously dead, and at least a third of the woody growth gets trimmed back to a green leaf node.

If I bring them into the house for winter, they just get loaded with bugs, so I’ve been banishing tropicals into the darkness for seven years now, and I haven’t lost a plant yet.

Have you overwintered plants with this rather cruel but effective program? If so, what has survived for you? Let me know which plants can take it — I’d like to try more, even if it means kicking my car out of the garage.

Mary-Kate Mackey, co-author of “Sunset’s Secret Gardens — 153 Design Tips from the Pros” and contributor to the “Sunset Western Garden Book,” writes a monthly column for the Hartley Greenhouse webpage and numerous articles for Fine Gardening, Sunset, and other magazines. She teaches at the University of Oregon’s School of Journalism & Communication. She writes about water in the garden twice weekly for Diggin’ It. 

Editor’s note: Click here to read "How to overwinter tropical fruits and other tender plants." To read more by Mary-Kate, check our blog archive. Gardening articles on a variety of topics can be found at the Monitor’s main gardening page. Also see our RSS feed. You may want to visit Gardening With the Monitor on Flickr. Take part in the discussions and get answers to your gardening questions. If you join the group (it’s free), you can upload your garden photos and enter our next contest.

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