Green Culture Singapore
Feature Article for October 2006
 
     
 
Pictures & Text by Tan Hong Yee
 
     
 
Online on 31 Oct 2006
 

Many carnivorours plants (CPs) originate from areas that experience distinct warm and cold seasons, unlike the relatively monotonous weather we get here in Singapore. As a result, those which have adapted, slow down their growth and enter dormancy, or a "winter" rest. While some plants may be able to adapt to our local weather and allow you to get away with not providing a proper dormant period, the majority will eventually waste away or tire themselves out - so to speak - usually after 2 years or so. While the exact mechanisms that trigger dormancy in CPs have not been ascertained, it is believed that a combination of several factors play a role. Local growers have therefore tried to mimic the conditions that these plants experience during their dormant period, including:

(1) Cold temperatures

(2) Minimal watering

(3) Decreased photoperiod

That being said, there is no one "correct" way of providing your plants with a dormant period, and your mileage may vary. This article presents 2 methods that I have found to be successful - the classical cold dormancy, and a dry dormancy (not to be confused with the hot dormancy seen in some winter-growing CPs, such as tuberous, pygmy and petiolaris-complex of Drosera).


WHICH PLANTS NEED DORMANCY?

Of the commonly-grown CPs amongst hobbyists here, this is just a short list that is nowhere near comprehensive:

Dionaea muscipula (Venus fly trap)

Drosera - cold-temperate species and forms

Pinguicula - cold-temperate species

Sarracenia species and hybrids

Utricularia - usually the very few that produce tubers or turions in winter

 

RECOGNISING DORMANCY, PREPARATION & PRECAUTIONS

One of the fundamental rules is: do not force dormancy on your plants - if they are ready, they will start entering dormancy on their own. Therefore, our role is to recognize when they need a rest, and to provide conditions required for this rest.

Unfortunately, this is usually the trickiest part. The recognition of dormancy especially in the tropics is rather an art more than exact science, and cruelly tests your observational skills. Different genera, species, and even plants of the same clone can present differently when they need a rest, but these are some clues for recognizing dormancy:

(1) Time - Raise your index of suspicion according to where your plants originated from, and what's going on there at this time. Those from the northern hemisphere experience their cold dormancy anytime from November till March, while those from the southern hemisphere follow suit from May till September.

(2) Growth - Drastically-reduced rate of growth.

(3) Size - Serially-decreasing size of leaves and traps.


(4) Form - Many CPs produce specialized leaf structures during winter, and these are an excellent clue to follow. Most notably, Dionaea tends to form ground-hugging leaves usually with smaller traps and larger petioles; temperate Drosera and Pinguicula form tight rosettes of buds (hiberniculae); some Sarracenia form non-carnivorous leafy structures (phyllodia). Once again, exceptions do occur - there are some Dionaea forms that grow in a ground-hugging fashion most of the year, while some Sarracenia such as S.oreophila and some of its hybrids form phyllodia not during winter but at the height of summer.

 

Left: Dionaea muscipula "Shark's Teeth" - summer growth form.

Left: The exact same plant shown above, postively screaming for dormancy. Notice the ground-hugging growth form, widened petioles and smaller traps.

Left: Healthy, trap-forming growing tips of a Sarracenia plant, fresh out of a dry dormancy and with a flower bud to boot!


Left: New leaves of a Sarracenia just going into dormancy. Note the weakly-formed leaves devoid of the normal trap shape. As these grow out, they form phyllodia instead - leafy structures that do not function well as traps.

Once you are fairly sure that your CP is going into dormancy, doing a few things in advance will help greatly. First, gradually - GRADUALLY, not parch them! - reduce the amount of water they are receiving. I usually take them off the tray watering method and start watering them as per normal houseplants, allowing the peat to become just barely moist before watering again. Second, gradually decrease the photoperiod. This is exceedingly-difficult to achieve in Singapore, but an acceptable way is to place them at a east-facing location where they receive only direct morning sun. If not, simply placing them in a shady position would also suffice.

Once again, no strict rules on this - but I usually prepare this pre-dormancy treatment for at least 2 weeks before starting on the real thing.

 

COLD DORMANCY

Cold dormancy eventually involves putting your plants to rest in a cold, slightly-moist environment, usually the crisper (vegetable) compartment of a regular fridge.

First, remove the plant carefully from its pot. Remove as much old peat from the roots as possible, and inspect the plant and rhizome for any old, dead and dying leaves. These should be snipped off to prevent the growth of any fungus.

Left: Dionaea freshly-removed from their pots.

Left: Trimmed and washed - for Dionaea, I remove the older roots as well

Left: Likewise for Sarracenia, old leaves are trimmed down.

Remember that cold + dark and damp + dormant plant = fungus galore! As a further precaution, lightly mist the entire plant with a mild fungicide. I've been using a simple one, Captan, for many years with good success.

Wet some dried, long-fibre sphagnum and squeeze most of the water out so that the sphagnum is just damp. You can spray this sphagnum again with fungicide if you wish.

Find a suitable plastic bag. I like to use those with holes already punched into them, to encourage some air circulation. However, this also means that the sphagnum will dry out much faster than if you used a sealed bag. Layer the bottom of this bag with some of the sphagnum, place your CP on top of the sphagnum, and finally cover the plant up with more sphagnum.

Right: Bottom layer of damp sphagnum, in a bag with holes.

Right: Next layer - the Dionaea themselves.

Right: Finally, covered with a top dressing of sphagnum.

Remember to label the bags! Use a marker pen to indicate the plant's identity and especially the date of dormancy. Seal the bag up, and place it into the crisper compartment of your fridge. The bags should be checked about once a week for any signs of fungus, and also make sure that the sphagnum remains damp.

Right: Whole fridge filled with dormant plants!

Right: Sarracenia lost to dehydration and fungus while I was away on holiday.

 

DRY DORMANCY

Instead of using a fridge, I find that dormancy can also be achieved outdoors. I favour this method for its simplicity, and the plants still seem to do just as well as those with a cold dormancy. For a dry dormancy, the pre-dormancy treatment becomes of utmost importance, and can stretch for as long as 4 weeks. At the end of this period, place the plants - pot and all - in a shady area which does not receive any rain.

Watering must be strictly controlled such that the peat remains just very, very, very barely damp all the time. Never overwater, and never let the peat go bone-dry either! This is especially useful for the less fussy, such as Dionaea, Drosera and most Sarracenia hybrids.

Left: Pots of Sarracenia taken off the trays and put aside for pre-dormancy treatment before a dry dormancy.

 

ENDING DORMANCY

The period of actual dormancy varies, so your best bet would be to observe the plants for any signs of vigorous, new growth. This typically takes about 2 months for most plants, and 3 months or more for plants with naturally-extreme localities such as Sarracenia purpurea ssp. purpurea. Once new growth starts, pot the plants back up and commence watering slowly, and they can eventually be returned to the tray system once growth has become steady and vigorous.

Right: Signs of new growth on a Dionaea, after 2 months in the fridge. Note the now-upright new leaves, in contrast with the old winter leaves with large petioles.


ABOUT THE AUTHOR & ACKNOWLEDGEMENTS

Green Culture Singapore (GCS) would like to thank Hong Yee for sharing this informative article with our members and now, with CPers on the World Wide Web!

Hong Yee is currently a moderator for the Carnivorous Plants Section of the GCS forum. He has been keeping these CPs since 1994, experimenting with varying outcomes on growing carnivorous plants in Singapore.

Visit his personal website, named "Little Garden of Horrors" at http://singaporeflytraps.batcave.net/, after the famous 1982 broadway hit "Little Shop of Horrors". There is an introduction to CPs in general, as well as tips on growing them successfully, especially in hot, lowland climates like Singapore.

 


 


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