Overwintering Container Hibiscus

3 years ago

Hi all! I'm looking for some advice on inducing dormancy in my container hibiscus plants. They're indoor south-facing windowsill plants. Last year I kept them in the window growing with the occasional flower, but this year I'd like to experiment with inducing dormancy. My research brought me to a few comments, including by Al Tapla, indicating I can relocate them to a dark cool place and allow the soil to dry out, limiting waterings to light and occasional. Presently I have only a cursory understanding of the biology of dormancy, basically that metabolism slows down until X or Y happens.

Are there best practices for inducing dormancy? What changes should I watch out for? Any advice on inducing dormancy, dormancy in general, or hibiscus care is very much appreciated. Understanding and encouraging the natural ebb and flow of my plants through the seasons feels like a great next step in learning to enable happy plants, I look forward to learning more and appreciate any resources or wisdom shared.

Thanks much in advanced!

Featured Answer

tapla (mid-Michigan, USDA z5b-6a)

3 years ago

You won't be able to force a predictive dormancy, which is a condition plants enter before the onset of adverse conditions. For example, photoperiod and decreasing temperature are used by many plants to predict the onset of winter. Consequential dormancy occurs when organisms enter a dormant phase after adverse conditions have arisen. For hibiscus, low light and fertility, soil only slightly moist, and cool temps will cause the tropical varieties of hibiscus to enter a state of quiescence, during which growth will be almost nonexistent. This treatment is useful for over-wintering many plants that will tolerate short periods of chill near the freezing point but do not need a cold winter period of chill to 'break' the dormant state, as most temperate deciduous plants need.

I have a cubbyhole in the basement where the footings/foundation juts out in a U-shape. It is designed to support a poured-in-place cement porch. I can walk right through the opening in the wall for access from the inside. It stays quite cool in the winter as it's not insulated. I'd guess the average temp range is about 50-55* until about mid-May. I've over-wintered plants like hibiscus, lantana, brugmansia, geranium, as well as bulbs, tubers, corms of a variety of plants.

Changing topics ...... hibiscus badly wants to be fully repotted every spring. Their root systems are prolific and grow very quickly, and tight roots will cause loss of many bloom buds once root congestion reaches the stage where the root/soil mass can be lifted from the pot as an intact unit. Our last frost date is listed as May 15. That's when I repot hibiscus and bring soil moisture levels up. I can usually always plan on having the plants outdoors around Memorial Day and they will have begun pushing new growth by then. All winter growth and plenty of last year's wood gets pruned off during the repotting session. If you keep the plants quiet during winter, they will greet spring with a greater measure of enthusiasm had you tried to grow the plant all winter. That treatment, indoors, seriously eats into the energy reserves that would otherwise be devoted tro the spring push.

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Comments (9)

Embothrium
3 years ago
last modified: 3 years ago
I don't think your evergreen tropical flowering shrubs that grow happily in full outdoor sun in places like Honolulu will benefit from such treatment. And am wondering what the point of it would be. Otherwise if you are located in the north seasonal outdoor conditions will affect their behavior even in the south facing window.
itplants
Original Author
3 years ago
Thanks for your response! Window space is at a premium with the season change and bringing plants indoors--if I have an opportunity to liberate those spots for plants that cannot enter dormancy I'm interested in doing so.
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Embothrium
3 years ago
What about setting up some artificial lighting?
itplants
Original Author
3 years ago
I love grow lights and use them on most of my seedlings and rehab plants--I don't want to build out more grow light space at this time if avoidable. I've got lots of options of keeping the plant awake over the winter, but I'm hoping to learn more about dormancy in general and whether I can induce dormancy into my hibiscus over the winter without major loss in vigor. One reason for this is the soil needs a changing badly and they're begging for an aggressive prune however I don't want to repot until Spring so that new growth has tight internodes and the plant has long days to recover in.
Vladimir (Zone 5b Massachusetts)
3 years ago
Al, are the plants you over winter in the cubbyhole in the dark or do you supply light?
tapla (mid-Michigan, USDA z5b-6a)
3 years ago
Since I grow under lights in the basement and lights are on/off 16/8 hrs, there is a small amount of light that manages to make its way through the opening despite the curtain that covers the nook, but it is negligible - very close to being able to say no light at all.

Al
Vladimir (Zone 5b Massachusetts)
3 years ago
Al, thank you for your response. It gave me the idea to overwinter my hibiscus, geraniums and maybe some others in my cool, dark basement. I already over winter my bananas (after removing all leaves) using that method.

One more question: do you do anything to the plants you put in the cubbyhole like pruning them back to minimize transpiration, etc.?
tapla (mid-Michigan, USDA z5b-6a)
3 years ago
last modified: 3 years ago
The plants that will tolerate a frost but don't need a cold rest are allowed to be knocked back by a freeze. I also try to defoliate whatever goes into the cubby hole when I give the plants the first drink. For plants with thick/ fleshy leaf petioles, I use a pr of scissors to cut through the leaf stem anywhere between the main part of the leaf and it's attachment point (to the branch/ stem). For thinner petioles, this tool is a very quick/ easy defoliator that stays sharp for a VERY long time:

Al