Dend. phaleanopsis type spike initialization
 

I have a nice purple NOID Dend. phalaenopsis type that has grown well for me and has put on about five new spikes in my care. It has bloomed once previously in my care, but only one spike with two flowers. My question is, two or three of the spikes matured but did not immediately produce a spike. Instead, there was a small dry nub at the top of the spike. A couple of weeks ago when watering I noticed that two spikes had started to develope from two of the canes. Is this delayed development normal? Is it initiated by shorter days or cooler nights? I haven't turned the heat on yet and a few mornings the temperature has been in the 65-67 F range.

Any enlightenment would be appreciated.

Bump. I don't know.

I am pretty sure my two den-phals are "cool weather induced" bloomers. Mine reliably start producing their spikes as soon as the temperature starts dropping, and did so again over the last three weeks or so. One of them is a typical purple no-id den-phal that you see photos of all the time. I would say keep them cool for a while longer if you can, you might get more spike, I have 5 on one plant.

I thought it was primarily temperature related as with Phals, but found an article from 2004 by Roberto Lopez and Erik Runkle at MSU where they state that Phal type Dendrobiums are in fact short day plants.

https://staugorchidsociety.org/PDF/F...opezRunkle.pdf

Here is the paragraph of interest:

"Dendrobium phalaenopsis requires short
day - lengths and warmer temperatures
for flowering. For example, flower-bud
development and flowering of plants
placed under nine-hour daylengths at
64 F (18 C) were accelerated by six
weeks compared with plants placed
under longer daylengths at the same
temperature (Rotor, 1952). A similar
response was observed at 55 F (13 C),
but flower bud development was slower
due to the cooler temperature."

Interesting. Not going to argue with that, just to note that these plants are under a grow-light (low quality screw in LED bulb) 12 hours a day and in a bright window. I can imagine the grow light doesn't put out enough light to matter tho. My living room temperature drops to 16-18c overnight so i assumed it was the cold. According to google we have 11.5hours of daylight these days, but I guess being indoors it could appear closer to the 8-9 hours.

Thanks for the correction. :-)

I tried to find the 1952 paper, but it's old and seems it was never scanned and uploaded anywhere. I think the keyword in this paragraph is "accelerated". 9h photoperiod leads to earlier flowering than under a longer daylength, but there is no mention of what longer actually is, now the effect on flower count. I also tried to find some scientific literature on the topic, but Phal type Dens have not been studied very much compared to the Nobile types!

I can't speak to the paper, but my den phals throw spikes in early/mid summer with temps in the 90sf and high humidity. They do this consistently, year after year. And has been said elsewhere on the board, they seem to thrive on gentle neglect.

This is all interesting. Mine are under lights but the room has windows, although they are not toward the windows. The room is not heated at the moment, so days are warm, nights cooler. One of mine, my old standby, has blooms. The other, fancier hybrid, does not. Seems to be no rhyme or reason here.

I alluded to, but did not say explicitly, that I am an indoor grower. The plant is on a bakers rack about 1ft. inside of a Southwest facing 6 ft. doorwall. Humidity generally runs around 50-60%.

Same conditions here. I'd also like a "concrete" answer.