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Thread: Raised Bed Advice???

  1. #1
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    Default Raised Bed Advice???

    I have started a raised bed. It is just a small project - it stands 4 feet high, 4 feet wide, and 8 ft long. I have the rows running north-south, and it is filled with compost and high quality organic soil, peat, and nutrients.

    The plants I'm trying in the bed are chard, broccoli, beets, radishes, lettuce, and carrots. All have been transplanted and appear to be doing well so far.

    I have a question about the cover.

    I currently have a sheet of visqueen anchored down over 1" PVC hoops. I have noticed a lot of condensation forming on the plastic. I know this set-up will hold moisture very well! (How much is too much, though?) I have left the sides open to some degree to let fresh air in and stale air out. Is this enough? Or should I cut ventilations slits in the plastic? I have seen both recommended and am wondering if anyone else has advice.

    Thanks!

  2. #2

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    I'd say leaving the ends slightly open is just fine for now. Keep monitoring the condensation build up and if it appears to be building more and more, open the ends farther. Some condensation is just fine and is going to happen (even just from plant transpiration). But you don't want it like a sauna either. Once your veges start getting leaves, keep a close eye to make sure mold isn't growing on them. That's what I'd do before cutting slits in the plastic anyway.

  3. #3
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    I bet you see condensation in the morning and then it's gone in the day, right? Unless you sealed the edges don't fret about it, it should be leaking enough air to stay healthy. We have a very similar setup in the yard right now. Spinach and onions are shooting up like it's summer.

  4. #4
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    In a hot area, I wouldn't go too much over 80% humidity.

    The standard rule for passively ventilated greenhouse/hot house structures is that approximately 25% of your floor area should be available in ventilation. Whether that's merely a flap of visqueen that you manually fold back during the heated times of the day/week, a thermo-coupler/thermostat rigged to an electric circuit that opens louvers or raises a curtain, or a heat-activated greenhouse vent jack that opens a panel/window/vent when ever it reaches 70-75 degrees f. (growing wider in its opening as it gets hotter) is up to you. There's LOTS of options out there.

    Bear in mind that the warmer a given space is, the more volume of moisture the air can hold. 80% humidity in an 80 degree f. room is a whole lot more actual moisture than 80% humidity in a 60 degree room. The saturation points of the two rooms are completely different, in terms of actual moisture content. That's why you're seeing moisture droplets when it's cooler out, and fewer when it heats up; the air's better suited to hold or absorb more moisture when it's warmer.

    As far as your rows, and their orientation to the compass points are concerned, I went with East-West beds long ago; it allows me to plant the vining or taller plants in the northern-most bed, running east-west, and then planting each subsequent row to the south with slightly shorter plants, decending in height as the rows progress southward. In theory, this permits less shading of the plants, hiopefully maximizing sunlight for all of them..

    It's worked pretty well thus far..

    Good luck.

  5. #5
    Member big_dog60's Avatar
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    I wouldn't be too worried about the condensation as long as you have sufficient drainage for your beds and keep them ventilated when it is warm.

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