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deandreamgreen

lowering temperature

deandreamgreen
16 years ago

Hi. I am brand new at gardening, much less using grow lights. I just started some mustards, chinese cabbage, pak choi, and tatsoi. They've germinated and I've moved them into the basement under T8 lights.

Ideal growth temperature is around 60 degrees with a max at 70. My temperature under the lights both day and night is approaching 75. Any ideas about how to get the temperature down closer to the ideal range?

There are vents for the central a/c down there; but it's an older house and I have those baseboard registers upstairs that I don't see a way to close; so I'd freeze myself out. Plus, there's the expense.

There are a few small windows that open in; but they only open partially and have no screens.

I guess I could buy some fans; but isn't having those blow on these tender seedlings going to kill them?

Thanks in advance to anyone who can help me out.

Comments (5)

  • shrubs_n_bulbs
    16 years ago

    Fans are the perfect solution. Use gentle fans or place them far enough away that the seedlings don't get blown away the first day, but imagine the winds a plant must cope with outside. Very soon they'll be able to handle a gale and be all the better for it.

  • deandreamgreen
    Original Author
    16 years ago

    I went out and bought 4 fans to surround my grow table and haven't seen any lowering in temperature. Do I need more fans? Should I put the fans on high and let them blow the the grow lights around? Is there a specific way the fans should be placed as far as distance and height? Or did I just waste my money?

  • deandreamgreen
    Original Author
    16 years ago

    I had another question related to the temperature issue. I guess it makes more sense from a strictly temperature point of view to have the lights on at night and have their rest period during the day.

    But does this screw up the plants "time clock" (if they have one), for when they are transplanted outside?

    I guess you can tell I didn't do real well in science.

  • shrubs_n_bulbs
    16 years ago

    If you wish to keep the temperature constant then it may make sense to have the lights on at night and off during the day (no natural light). The plants will adapt to changes in the exact timing. But most plants want to be cooler at night, it is warm nights more than warm days that make them stretch. You should try to provide at least a 10F temperature drop each night, even 20F although that can be difficult indoors. Again the Impatiens will deal best with warm nights and you probably don't want them colder than 55F during the day. During germination you should aim for a constant 70F-75F or even a little warmer. The others prefer cool nights, pretty much as cool as you can get indoors.

    Even without a temperature drop in the room as a whole the fans will keep the plants cooler and help them to strengthen. The lights shining on the dark soil and being absorbed by the plants makes them warmer than the air in the rest of the room. If the whole room becomes too warm then you need to vent the air. Blowing it into a cooler part of the house may be practical, or you may need to vent to the outside. In many cases, sucking outside air into the room is more effective. Remember it can take quite a while for small fans to make a difference to the temperature. In one of my enclosed propagators I even found the temperature at the plants rose when I switched on a fan because warm air from the lights was being moved down to plant level. I changed the design to vent air from the lights away from the plants.

  • shrubs_n_bulbs
    16 years ago

    I meant you don't want the Impatiens colder than about 55F at night.