Temperature and humidity for seedlings?

thebAse

thebAse

Active Member
What temperature and humidity levels should I be aiming for with my seedlings?

I have 10 tiny sprouts in a propagation tray with a heating pad and humidity dome under a 400w metal halide light. They are only about 48 hours old and I'm wondering how to tweak their growing environment for optimum growth over the next couple of weeks.

Thanks!
cool.gif
 

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Watch your plants closely when there that young under such a powerful light. The intensity of the light may harm your fragile babies. I like to use CFL's until there 2 weeks old. One of my first times growing, my seedlings died and i couldnt figure out why and a buddy of mine told me that my light was to intense for such a young plant. My light is a 1000W MH so im sure theres a big difference.
 
Hydroflo said:
Watch your plants closely when there that young under such a powerful light. The intensity of the light may harm your fragile babies. I like to use CFL's until there 2 weeks old. One of my first times growing, my seedlings died and i couldnt figure out why and a buddy of mine told me that my light was to intense for such a young plant. My light is a 1000W MH so im sure theres a big difference.
Click to expand...

All depends on the distance away from the bulb and how many your are veging, I myself used some cfls and got them real close but still experienced stretching, so i stuck to using the metal halide at the time then to go from seed to give tight node spacing.
 
Ok, thanks =D. Ill def remember that. =D I just didnt want to take the chance again right away so i used CFL's, but now that im up and growing ill try experimenting with plants in seedling stage.
 
Actually, I just updated a mistake in my original post: the HID is 400w, not 600w... and the bulb is currently 16" from the top of the plants.

The light is not intense enough to melt the humidity dome, which is only about 10" away from the bulb... and I can leave my hand on top of the dome comfortably.

The temperature inside the humidity dome is about 85[SIZE=-1]° F when the light is on, while the relative humidity is a fairly constant 50%.

How do those numbers sound?
[/SIZE]
 
thebAse said:
Actually, I just updated a mistake in my original post: the HID is 400w, not 600w... and the bulb is currently 16" from the top of the plants.

The light is not intense enough to melt the humidity dome, which is only about 10" away from the bulb... and I can leave my hand on top of the dome comfortably.

The temperature inside the humidity dome is about 85[SIZE=-1]° F when the light is on, while the relative humidity is a fairly constant 50%.[/SIZE]

[SIZE=-1]How do those numbers sound?[/SIZE]
Click to expand...

If you pulled the light away a little further,say around 2 foot, the plants will be happier for it for one, and two the humdity inside the dome would increase because the temperature would drop slightly which wouldnt even concern you but the humidity would raise and then the plants would root faster and get into the veg stage a bit quicker.

Once you get the humidity dome off you will probaby want to keep the 400w around 12" away from the tops
 
Cool... thanks for the info!

Should I leave them inside the dome until they grow too big to fit?

Also, I've got a 1000w metal halide waiting for them after they outgrow the dome... how far should they be kept from that bulb?
 
Welcome to the forum. Sounds like you have invested in some lights and etc.
As soon as seedlings are above ground good as yours are they will be better off woth some air circulating around them. You may want to consider transplanting them soon. If you lift ine of those Rapid Rooters up and see roots its time to get them in some thing a little bigger, maybe there final pots depending on what system your are going to use and what medium. You may not want to use the 1000watt at all for only 10 plants unless you get an hps instead of the mh. 400watts will cover 10 plants no sweat. Once you get them out of the propagation dome aned transplanted, begin moving the light down an inch or two each day. The plants will grow up some to meet the light. When the light in about a foot a way from the tops of the plants, start moving the light back up.
With hid lights making sure you have good ventilation is as imporant as the distance the plants are from the light. VV
 
Thanks for the welcome VictorVIcious!

I have both a mh bulb and a hps bulb for the 1000w ballast... it's an electronic ballast that accepts either type. I did invest in some quality equipment! ;-)

Ventilation is taken care of, so I shouldn't have to worry about air flow for the plants... or heat buildup.

My plan is to hopefully get 3 or 4 good mothers from the plants I've got growing now... keep those vegging under the 400w light using an autopot system... and grow 16 to 24 clones under the 1000w bulbs using a 4' x 4' ebb and flow system. (So, I'll be asking a lot of questions over the next couple of months.)

How does that sound?

For now, I'd like to get some more input on when the seedlings should be removed from the humidity tray... I've heard different things... some say to keep them in for a week... until they've almost reached the top of the dome... or, as you suggested, only until they're above ground.

Any more comments or suggestions? Thanks!
 
Photo update... 72 hours since planting... approximately 48 hours since sprouting...

You can see the difference from the earlier pics... which were taken about 12 hours ago!
 

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I have done it both ways, under the dome and out, but I wouldn't use the hid for small seedlings anymore. When you do you can't get the light close enough and they will stretch to reach it. First time I did it I thought it was great. They were growing so fast. After proping them up, and tying them up over the next two or three weeks, I decide it was better to use good quality floro's for the first couple of weeks.
I put an ocillating fan blowing real gently across them. It helps to strengthen the stems. You can put the floro's right on top, almost touching the plants and if you get the right bulbs for about $50.00 you can get a 4' fixture that will do fine for 10 plants. After a couple weeks they can take the heat better so they won't have to stretch for it.
 
Id take the 400 watt light off these you can shock them at this early of a stage with that intense light and it can cause drying to fast. Just get a simple 4 foot florescent shop light and keep it within 2 inches of the plant tops to stop stretching and get best results wait til week 2-3 for using the bigger lights like the mh.You wont need the dome for these really just mist them twice a day. Keep a spacer between the heat mat and the tray bottom I used 4-5 pencils.It allows heat and air to flow in between making heating move even without chance of heating the roots.Keep air temp around 75 for the young plants and humidity is good by light mistings 2-3 times aday.Not to heavy though
 
Everyone seems to agree that the 400w MH is too much for the small seedlings so I'll make a visit to the hardware store to see if I can find some appropriate fluorescent lighting.

While they're still under the HID, what warning signs should I look for that would indicate they're not appreciating the light intensity?
 
Getting to tall for the stem to support, drooping leaves, stem etc. You have the light high enough at 16" that it might not be a big problem. You might just end up doing what I had to do, tying them up. If you do need to do that I recommend buying wooden skewers. You can usually get them at grocery stores for about a buck. When you get ready to transplant just stick one in close to the little plant. When the stems have strengthend you can pull it back out. VV
 
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