Watering from Bottom

Bill1897March 14, 2012

Hi All,

I've just started seeds for eggplant, cherry tomatoes, beefsteak tomatoes, cantaloupe, watermelon, strawberries,onions,lettuce, stevia, and a bunch of other plants. I am in a zone 6B. I have four 72 cell seed starting trays and I was wondering when I water from the bottom, how much do I fill up to on the tray (.5", 1", 2", 3", etc) and for how long?

Also, I would like to mix in some 3% hydrogen peroxide (when I water from the bottom) to really ensure no mildew or damping off forms. What is the best ratio of hydrogen peroxide to water? I've heard people recommend a ratio as high as 1 cup h2o2 for every 1 gallon h20. This apparently isn't dangerous for the seeds because 8 ounces of 3% diluted hydrogen peroxide in 1 gallon is only .24 oz of hydrogen peroxide in 136oz of water-- only .17%. I don't even know if this is enough to be effective. I've heard plants can tolerate as much as 5% hydrogen peroxide concentrations, implying that the h2o2 could be applied directly from the 3% solution bottle--has anyone tried this; would this concentration be safe for the seeds/seedlings; and any warnings or experiences that would be helpful?

Lastly, I have the starter lids on and a lot of condensation has formed on the lids. I've only watered them the day I sowed them, which was 3 days ago. As long as there is moisture on the lid I shouldn't water, right? I'm begining to worry about mildew forming from all this condensation so I'm thinking about taking the lids off and letting the trays aerate. If I do this how should I check to make sure when it is time to water and approximately how long between waterings (I know it varies but I'm looking for an approximation--I've heard two days sound about right).

Thanks for all the help.

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flora_uk(SW UK 8/9)

There have been two recent threads on this. One is linked. The key is to learn as quickly as possible how water behaves in your potting medium and to recognise when it is needed - and, even more important, when it is not needed. You can always refresh a seedling which lacks water but you can't wring it out when it's drowned. It is not possible to give rules. If watering is done properly you will not get damping off or moulds and there will be no need for prophylactic measures. I would not play around with any 'cures' until or unless a problem arises.

You can fill the tray as deep as you like. The important part is tipping out excess water after you see the surface of the medium go damp. This could be 10 minutes or 2 hours, it depends on the conditions so, again, I can't give a rule. With experience you will find that you can judge the amount needed and there will be no need for tipping out. The medium will absorb all you give it.

Regarding the lids, condensation doesn't necessarily mean there is enough moisture in the medium. It might just be coming from the surface if you have surface watered and the bottom may be dry. It is fine to give the trays some fresh air by lifting the lids every so often. Remove the lids when the seeds have germinated. (This is the recommendation - actually I don't but I know how the seedlings are doing so can judge it).

Here is a link that might be useful: Previous thread.

    Bookmark   March 14, 2012 at 2:22PM
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It definitely matters what potting soil you use. I have one tray that when you water from the bottom takes 10 minutes. Another batch (with cheap potting soil) takes much longer. The medium does wick as well. I have to additionally water lightly from the top. It's a pain. You get what you pay for!

    Bookmark   December 27, 2013 at 11:49AM
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digdirt2(6b-7a No.Cent. AR HZ8 Sun-35)

And as already mentioned, normally the humidity domes should be removed once germination happens. Extended use of them is the primary cause of damp-off and other fungus and mold problems. At the very least, prop them open so air can circulate.

Search here will pull up many previous discussions for you on these issues.


    Bookmark   December 27, 2013 at 9:01PM
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digdirt2(6b-7a No.Cent. AR HZ8 Sun-35)

Also, curious as to why you started all these seeds so much earlier than normal for your zone? How do you plan to keep all of them alive and healthy until they can be transplanted into the garden?

Good luck.


    Bookmark   December 27, 2013 at 9:04PM
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floral_uk z.8/9 SW UK

Hi digdirt - don't know if you noticed this is an old thread originally from March 2012 which has been revived.

    Bookmark   December 28, 2013 at 6:49AM
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digdirt2(6b-7a No.Cent. AR HZ8 Sun-35)

No I sure didn't. Thanks Flora. :)


    Bookmark   December 28, 2013 at 6:36PM
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