Saturday, January 22, 2011

How to grow Sarracenia to perfection - about dormancy

Sarracenia during dormancy, with summer growth removed:

Dormant greenhouse

The same plants in full growth, taken a few months earlier.

Greenhouse_full growth 
Sarracenia avoid the harshness of winter in the cool temperate climate of North America by halting growth and waiting until the cold has passed. This behaviour is called dormancy. In plants, dormancy is triggered by changes to day length with the seasons, not by cold. The cold itself does not play much of a role in starting dormancy, but it can keep plants dormant once dormancy has started.
A tray of dormant Sarracenia flava in my greenhouse. Note the traps are dying off from the cold - this photo was taken after a week of frost at the start of winter.
Depriving Sarracenia of a good dormancy (ie. forcing them to grow year round) will cause them to grow weakly because of stress. It does not seem to be possible to kill Sarracenia by cold in Australia, but it is possible to kill them if they don't get good changes in season. Dormancy for Sarracenia grown under Australian conditions always begins around the autumnal equinox, and starts again after the winter equinox if temperatures are warm enough. I am not aware of any research that has identified the exact triggers for Sarracenia, but I think it would be a really interesting topic to study. It is interesting to read that Sarracenia in the tropics (Singapore) can start to enter dormancy by themselves at the height of the monsoon season - possibly because the dense cloud cover increases the amount of far-red light, which also occurs as days become shorter in autumn.

Sarracenia trimmings – these were taken a little early to try and stop a mealybug infestation.

Dormancy may seem a boring time for those growing Sarracenia, but I think it is a really important stage in their growth cycle. It is when all dead and dried parts of the plant can be removed, but it can be a good idea to leave some leafy material on plants if you live in an area that gets many winter frosts. The remaining vegetation seems to act as a blanket, trapping slightly warmer air stopping the really cold air from burning the live tissue in the rhizome. Late winter is also the time to repot your plants.