Hi all,
When I grew astrophytums in temperate regions, all would flower unfailingly during spring. This is unsurprising - literature is quite clear about the necessity of a cold winter for this genus to flower. However, since living in the tropics, I have been forced to use growlights (good quality 200W ones), and now am no longer able to observe any discernible flowering patterns - my cacti do so sporadically and throughout the year.
This is unlike the Thai and Malaysian nurseries just next door whose astrophytums appear to keep to a certain flowering 'season' despite similar tropical climates. From my understanding their greenhouses have day-time highs of 45C and night-time lows of 25C. This leads me to believe that extreme fluctuations in day/night temperatures or perhaps an extended period of high temperatures (during the dry seasons) may also be triggers for flowering.
I would like to hear from more experienced growers. I have been attempting a small-scale breeding program but since I am not able to predict flowering I have been forced to freeze pollen whenever I can.
H
What triggers flowering in astrophytums?
Re: What triggers flowering in astrophytums?
If your using grow lights it could be a photoperiod problem unless you are observing the correct daylength versus night or dark length to induce flowering. If they flowered in spring before that would indicate they are short day species and longer light periods will simply induce growth rather than flowering?
http://cactus-art.biz/note-book/Diction ... period.htm
https://en.wikipedia.org/wiki/Photoperiodism
"Generally, short-day plants flower when the daylength is shorter than 11 hours and long-day plants will flower when the daylength is longer than 14-16 hours. Keep in mind, however, that the critical daylength is likely to be somewhat different for each species."
https://ag.umass.edu/greenhouse-floricu ... ing-plants
As the link above says in countries with long days or if flowering out of season is desired a shorter daylength can be achieved by covering plants with a black cloth or tent, but that is a chore every day for the dark period desired. If using lights you probably just need to adjust the length your lights are on for and give a longer dark period.
If you are attempting producing new hybrids you may need to keep the mother plants under a shorter lighting regime to produce flowers and fruit than the seedlings kept under longer daylength lighting to produce more rapid growth and thus reach flowering size quicker?
http://cactus-art.biz/note-book/Diction ... period.htm
https://en.wikipedia.org/wiki/Photoperiodism
"Generally, short-day plants flower when the daylength is shorter than 11 hours and long-day plants will flower when the daylength is longer than 14-16 hours. Keep in mind, however, that the critical daylength is likely to be somewhat different for each species."
https://ag.umass.edu/greenhouse-floricu ... ing-plants
As the link above says in countries with long days or if flowering out of season is desired a shorter daylength can be achieved by covering plants with a black cloth or tent, but that is a chore every day for the dark period desired. If using lights you probably just need to adjust the length your lights are on for and give a longer dark period.
If you are attempting producing new hybrids you may need to keep the mother plants under a shorter lighting regime to produce flowers and fruit than the seedlings kept under longer daylength lighting to produce more rapid growth and thus reach flowering size quicker?
Re: What triggers flowering in astrophytums?
Dave,
I'm not sure if photoperiod is the trigger here (though it may very well be one of them). If it was the main determinant I doubt that the astrophytums from Thailand or Malaysian nurseries will flower with any consistency. There was an interesting paper I read a few years ago from a Florida university that compared the flowering of cacti in two greenhouses - one with day-night temperature differentials, and one without. The one with temperature fluctuations was found to have significantly more blooms. I wish I still remembered it the title.
I will see what I can do about manipulating photoperiod though. Many thanks.
H
I'm not sure if photoperiod is the trigger here (though it may very well be one of them). If it was the main determinant I doubt that the astrophytums from Thailand or Malaysian nurseries will flower with any consistency. There was an interesting paper I read a few years ago from a Florida university that compared the flowering of cacti in two greenhouses - one with day-night temperature differentials, and one without. The one with temperature fluctuations was found to have significantly more blooms. I wish I still remembered it the title.
I will see what I can do about manipulating photoperiod though. Many thanks.
H
Re: What triggers flowering in astrophytums?
Greenhouse microclimates can play a large part in how plants thrive or flower. Two greenhouses on the same property may produce different results with the same species due to both having a slightly different microclimate. As you say day to night temperature fluctuations also may trigger flowering.