Which is most important for blooming...light or temp. difference??

[arleneg]

I bought my Milt. William Kirsh "Bread & Butter" and Phal. hybrid (dtps. Double Trouble x Zuma White Puff X phal. Penang Girl x George Vasquez) two years ago. My milt. bloomed this past spring, but my phal. hasn't. The phal. has been under low-med (filtered) light, watered every few days, in 40-60% humidity. However, in the past year and half, it hasn't gotten any temp difference of 10-15 degrees until these past couple weeks.

So which is most important, light or temp. difference, to make a phal. bloom??

[Cynthia, Prescott, AZ]

It is not a matter of high light or low light, but the length of the day. Both cool night temperatures in fall AND the shortening of the day length trigger blooming in Phalaenopsis. As to which is most important, I don't really know. It would have to be someone with a lot of experience growing Phals. Since most of my orchid carrier involved killing Phals, I didn't get much experience in growing them. Cynthia

A recent addition: It appears that in nature, the cloud cover in winter is less, and Phals given more light in winter are helped to initiate blooming, in addition to all the other factors. C

[arleneg]

Cynthia, I guess, I just have to wait and see in the next month or so.

Thanks.

[jerrymeola]

Normally light is the most important factor with the possible exception of Phals.

Phals need both the right light level (but this is very low) and a temperature difference to set buds. For those who grow Phals indoors I recommend putting them outside for whatever month will give you 70 degree days and 50 degree nights. This will be earlier in the fall or later in the spring the further north you live.

The length of the day will also vary with the temperature, so I do not know if Cynthia's belief in the length of the day is more important since temperature, light levels and length of day usually go together

[arleneg]

In regard to length of day, how many hours in a day (in fall and/or spring)? All this time, I thought the longer length of day, instead of short days, contributes more to blooming.

Oh well...I'll find out, hopefully soon.

Btw, my dendrobium (sorry, don't know the name), which my mom gave one of her shoots to me and now has two canes, is spiking.

[Cynthia, Prescott, AZ]

Jerry, I got the data on temperature AND length of day from a commercial Phal grower that grew all his stock under lights, so I think the effect of day length was well established as important. He also said that any stress was a trigger for blooms, so we can add things like letting the plant get dryer than usual or maybe even a brief spell of too hot, but of course, what is too hot for a warm growing plant like a Phal? One might just as likely kill the plant. The other point he made was that he changed his flourescent tubes late winter and the sudden increase in brightness reinforce the seasonal change. Cynthia

[jerrymeola]

I do not disagree with anything the commercial grower told you but keep in mind that all (myself included) commercial growers draw conclusions based on what works for them.

Length of day is certainly a factor in plant growth. Poinsettias do not flower at Christmas naturally yet we see millions of them that were grown in greenhouses that control the length of day. That is the extreme case but it is reasonable that it has some effect on all plants to a greater or lesser degree. But it is very hard to shorten days.

I agree that stress often induces flowering sometimes at the expense of the plants health.

[Cynthia, Prescott, AZ]

I assume that this grower was supplying blooming Phals to the trade all year long, hence the need for growing under lights and probably in an airconditioned building and had an assembly line going for blooming Phals from the orient. The reason I consider this info important to newbies is that they often grow Phals in their home where the plant is in the same room with people, and most people go to bed at the same time each night leaving the lights on until they retire. So, my guess is that complaints of plants that don't bloom after a couple of years of growing them successfully may be caused by the light issue. Cynthia