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Fluctuating temps for germination

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Fluctuating temps for germination

Post  natsea on 5/5/2012, 4:34 pm

Hello. This is my first year gardening. My garden is in a zone 4 climate, so I started my seeds in a greenhouse about two weeks ago. I used a seed starting mix (vermiculite) in peat pots sitting in seed trays with the dome lids on each. I pour a little water in the tray and they keep the peat pots and soil moist. I am not using any grow lights or heat mats because it's not possible at this time, so I'm relying on the nice warm temps in the greenhouse during the day to do the work. I have looked at the germination charts in the back of the SFG book and my question is - will seeds still germinate well when the soil temps fluctuate a lot? I know most seeds need consistently warm soil temps and mine are getting nice warm soil temps in the greenhouse during the day (around 80 degrees), but at night, the temp drops considerably (to around 38 degrees lately). Will this fluctuation have a negative effect on my seeds? I planted them about 14 days ago and some are coming up (corn, squash, carrots, radish, cucumber), but others are not (mostly the lettuce). Thanks!


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Re: Fluctuating temps for germination

Post  plantoid on 5/5/2012, 5:57 pm


Temperature variations do affect all sorts of seeds in their germination. Depending on the severity and frequency depends on if the seeds survive or not.

It is a complex subject to give you an accurate answer because of the variations that can apply.

Look in the charts of Mel's All New Square Foot Gardening 2006 edition on page 267 and there is a chart of the temps needed.

Lots of folks start their seeds germinating in a warm dark cupboard such as an airing cupboard or on top of a fridge or freezer and as soon as they show signs of breaking throught they move the seeds else where , but the temperature drop will still affect many very small plants .

50 oF for over 12 hrs will often kill off any just about to germinate seeds , if the temp drops to 45 oF just a few hours causes problems to many seeds and seedlings in the first few days of emergence .

I have been taking trays of small pots of seeds out the greenhouse and bringing them inside to sit on the dining table ( with my lasses blessing Laughing ) for we have had a few cool nights .

here in my location tonight is forecast as a sharp frost down to minus 3 oC ( 43 oF ) , I've covered everything in the greenhouse with crop fleece. I have brought in loads of susceptable plants and newly sown seeds even though I have a low grade back ground heater in the greenhouse as it will not out do any decent level of frost.


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Re: Fluctuating temps for germination

Post  quiltbea on 5/5/2012, 9:35 pm

I agree wtih plantoid. The seeds need warmth to germinate. Can you bring them indoors at night?


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Re: Fluctuating temps for germination

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