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Thread: Photoperiod: how short is too short?

  1. #1
    Oh, the humanity!! TheFury's Avatar
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    Photoperiod: how short is too short?

    Hey everyone - Calling all sundew experts!

    I have four nice pygmy sundews, and I'm trying to get them to produce some gemmae so I can sustain their colonies. To achieve this, I've gradually lowered the photoperiod down from 16 hours to 9. I plan to leave it there until mid-February and then start ratcheting it up again.

    This may or may not be pissing my other plants off. I have a number of tropical dews, pings, etc. in the same rack along with my pygmy dews. My pings look VERY happy (even my struggling P. moctezumae is showing signs of recovery!). But so far, my D. adelae, D. alicae, D. spatulata "Fraser Island," and D. venusta appear to be in various stages of decline. I'm quite concerned about the D. adelae and D. alicae; the D. spatulata and D. venusta just aren't as pink and dewy as I'd like them to be.

    For those of you that grow sundews under lights, have you experimented with photoperiods this short? Might the plants be happier if I simply let them dry out a bit more?

    I'll post some pics up soon so you can see what the deal is.

    ---------- Post added at 09:47 PM ---------- Previous post was at 08:48 PM ----------

    As promised:

    D. venusta:


    D. aliciae:


    D. adelae:


    D. spatulata:
    Last edited by Joseph Clemens; 12-02-2010 at 08:13 PM. Reason: Nomenclature adjustment - D. alicae is actually spelled D. aliciae

  2. #2
    Tropical Fish Enthusiast jimscott's Avatar
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    I would go with ~10 hours as the lowest. Those plants have a ltitude between equatorial and temperate.

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    CPlantaholic's Avatar
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    You may notice that when you reduce the photoperiod, some plants may be more succeptible to root rot. However, I know droseraguy used a photoperiod of around 9 or 10 hours for most of his dews and they all did fine- so I'm not sure why I had such problems with my D. admirabilis, D. nidiformis, and D. adlelae etc. but I think it was related to the water levels. When I watered less frequently, less of them were prone to root rot or whatever the problem was...

    So unfortunately, I've since avoided lowering the photoperiod, and now I don't get gemmae anymore

    PS it appears that your water levels may be a bit too high for the D. aliciae since they're all developing humic acid on the crown. You can try wiping that residue off to give the leaves normal growth again. Venusta and Spatulata have done better for me in comparison to others in "wetter" soils, while D. aliciae typically does what you're experiencing. I don't know what's up with the Adelae though, unfortunately. Mine weren't too happy when I had recently transplanted them, even with a humidity dome. The temps may have been too cold at the time for them to transition like they normally do into the cooler temps (when already established). Perhaps it is still recovering from the old media. I can't tell if those little white specs on the newest leaves are tiny bugs or if it's just sphagnum dust residue from the recent transplant.

    How far away do you have the lights now? It looks like they're all gradually developing a bit more coloration, which is good. They could possibly all stand to have the lights even closer. Maybe a few inches closer. Higher intensity lighting tends to counterbalance the lower photoperiod's effects on my plants the year I was experimenting with the lower photoperiod, so you can see if that will help or not.
    Visit The Sundew Grow Guides: http://www.growsundews.com
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    Happy Growing!

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    Stay chooned in for more! Clint's Avatar
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    It looks like your D. adelae is planted in peat and sand with a topdressing of LFS.

    Replant into pure LFS or LFS and perlite. I've never hadit do well in anything less than an airy media like that.

    I never got into Pygmies so I cant help you with that, but 10 hours is the minimum I would go with 12 being better. Intensity is more important than duration, though, so no matter what have the lights as close as you can without encountering temperature problems.

    I always grew my Drosera with my nepenthes with a year long photoperiod of 16 hours, but in the spring and summer I moved the hardier ones outside where they do best after an acclimation into full sun.

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    Oh, the humanity!! TheFury's Avatar
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    Quote Originally Posted by jimscott View Post
    I would go with ~10 hours as the lowest.
    In your experience, do Pygmies still produce gemmae with photoperiods of 10 hours or more?


    Quote Originally Posted by CPlantaholic View Post
    PS it appears that your water levels may be a bit too high for the D. aliciae since they're all developing humic acid on the crown. You can try wiping that residue off to give the leaves normal growth again.
    Humic acid huh? Interesting. I tried scratching at it with my finger nail last night and it wouldn't budge; I'll try my luck with a damp Q-tip tonight. Thanks for the suggestion! I'll also let my plants go longer without watering - probably gonna leave my water level around 1" and let the bin go dry for 5 or so days before refilling. Sound reasonable?

    Quote Originally Posted by CPlantaholic View Post
    I don't know what's up with the Adelae though, unfortunately.
    Yeah, tell me about it! This will actually be the second adelae that I've killed... that is, if this one bites the dust, too. I don't know what's going on - I thought these things were easy! It was doing well for two weeks or so... growing quickly, producing dew... and now look at it! And I believe the white specks are just residue from the transplant.

    Quote Originally Posted by CPlantaholic View Post
    How far away do you have the lights now?
    Between the actual light tube and the rim of most of my pots, I measure about 7". Also, I was wrong when I said they were T5s in previous threads. They're actually 32-watt T8 bulbs.

    Quote Originally Posted by Clint View Post
    It looks like your D. adelae is planted in peat and sand with a topdressing of LFS.

    Replant into pure LFS or LFS and perlite. I've never hadit do well in anything less than an airy media like that.
    That's exactly the mixture I'm using. It seems that adelae are quite sensitive to repotting - do you think that yet another repotting in two months will push this plant over the edge? If not, I'm open to trying anything!



    So, is the general consensus that it's more of a water issue than light issue at this point?

    Thanks for all the responses everyone!

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    Tropical Fish Enthusiast jimscott's Avatar
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    As far as i understand, gemmae production is tied directly into reducd photoperiod. Whatever i had going for November, that was perfect (10 hours). Before and after that, I had almost nothing.

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    Oh, the humanity!! TheFury's Avatar
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    Hey, thanks. About how close were the lights to your plants? And out of curiosity, two questions: 1) How long after your photoperiod reached 10 hours did your gemmae start forming, and 2) how long did you leave the photoperiod that low before raising it back up to summer levels?

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    CPlantaholic's Avatar
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    Hey Fury, with my fixtures, when I use a single 2-bulb T-8 fixture then I get the bulbs within 2-3 inches of my plants for decent intensity. When I use 2 fixtures side-by-side, then I can obtain more intensity than that even when I have the fixtures 6 inches away or a bit more.

    And for me, it took around 2-2.5 months before mine produced gemmae the year I switched the photoperiod to 10 hours. I actually gave up and then noticed a few weeks after changing the photoperiod back to 15 hours that a few, like D. omissa x pulchella and D. roseana had gemmae. Other species didn't have gemmae at that point though, so they may take a bit longer?

    Here is an old post I had copied to my computer
    The 2 quotes of interest to me were:
    droseraguy: "In the fall I set the daylength to 10 hours and put in the basement 50-60 F. temps. After a few months they all seem to produce a bunch of gemmae. In the spring temps are upped to 65-70 and 16 hours of light. My D. scorpiodes is flowering with a band of gemmae around it's middle."

    Here's the original thread: http://www.terraforums.com/forums/sh...d.php?t=108218
    Last edited by CPlantaholic; 12-04-2010 at 11:09 AM.
    Visit The Sundew Grow Guides: http://www.growsundews.com
    New- Drosera video tours & other sundew info, now on YouTube!

    Happy Growing!

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