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rainbowgardener
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how cold is too cold?

I have had most of my tomatoes and peppers outside hardening off and they have been through some nights in the mid 40's with not too much stress. But tonight it is predicted down to 38. That's at the airport and I'm usually a couple degrees warmer. And it doesn't get below 40 until 5 AM and then by 8 AM it is above 40 again.

What do you think? Do I need to drag all those trays back in again? :shock:

TIA!!!
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hendi_alex
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Re: how cold is too cold?

We had a couple of similar nights and I erred on the side of caution. Too much effort has been expended to lose those babies at this point!
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applestar
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Re: how cold is too cold?

I would at the very least cover them. If 38°F is predicted in my area, I would bring them inside or double cover them with a porous material and a plastic sheeting. But my garden is always 2-3 degrees colder.

It will also depend on how warm the ground is. If it's been hot and the ground is warm, then covering will hold in the thermal layer.
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rainbowgardener
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Re: how cold is too cold?

Thanks for the really quick responses, guys! You know that wasn't the answer I wanted to hear, but 15 trays of plants have now come back in. The tomatoes are getting really tall and leggy. Really they should be uppotted again, but that is not going to happen. But when they go back out, they have to come off the morning sun only deck into more sun.
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JayPoc
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Re: how cold is too cold?

Coming from the guy that almost always plants tomatoes a little too early (aww, cut me some slack....I come from a long line of too early planters), the plants would have been just fine left out and uncovered. I've never had any loss or even the slightest damage even down into the lower mid 30s. Covered, I've survived nights right around 30 (but when that has happened, I REALLY cover them...usually an upturned bucket and a mound of compost or mulch). It makes for some uneasy nights, but again, they always have survived.

Now having said all that, I'm chomping at the bit to get my first few in the ground, but I'm still a little apprehensive. Tonight it is supposed to get to around 35. The 10 day forecast (going out to May 2nd) shows most nights above 40 with just one night with a low of 39. Our average last frost date is somewhere around may 5th through the 10th. If it still looks good tomorrow, I might put them in the ground after work. Sigh....what to do, what to do...

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hendi_alex
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Re: how cold is too cold?

I start by planting just a few, and then plant over a 2-3 week period, that way there is little chance that a late frost will affect more than a few plants.
Eclectic gardening style, drawing from 45 years of interest and experience. Mostly plant in raised beds and containers primarily using intensive gardening techniques.
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gixxerific
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Re: how cold is too cold?

First off 15 trays, I don't like the odds of not hitting that winning number. Best to be safe.

It is a pain but loosing all that would be more of a pain, sorry I know you don't to hear that. I moved in and out 50 7 - 10 gallon usually wet and heavy pots several times last year. Not good but needed.

Good luck RBG.

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Re: how cold is too cold?

Here is what Wiki say's about the actual temps and their severity. Though these seem rather low compared to other places I have seen it.

slight frost: 0 to −3.5 °C (32.0 to 25.7 °F)
moderate frost: −3.6 to −6.5 °C (25.6 to 20.3 °F)
severe frost: −6.6 to −11.5 °C (20.2 to 11.3 °F)
very severe frost: below −11.5 °C (11.3 °F)

I though it was
32 - 28 light frost
28 - 26 medium frost
26 - 24 hard frost
24 - ....... hard freeze

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rainbowgardener
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Re: how cold is too cold?

well, I knew it wasn't going to freeze, but cold weather even above freezing can set warm weather stuff like tomatoes, peppers, basil back, especially when they are tender seedlings and not totally hardened. At the end of the season, when cold weather comes back in the fall, I wouldn't worry nearly as much, they are much more toughened up by then.

I did bring them in and left them in until I could come home from work at lunch time. When I had to leave for work in the AM, it was still feeling chilly and windy. At lunch it was nice. I moved a lot of things in to more sun than they had been.

Tonight it is predicted down to 43 and everything will stay out!
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gixxerific
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Re: how cold is too cold?

Nice I figured it would be okay.

Now for me they are talking a couple mid upper 30 lows next Wed - Thur. Just my luck.


Again wishing you luck, us early planters need it from time to time.

mattie g
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Re: how cold is too cold?

gixxerific wrote:Here is what Wiki say's about the actual temps and their severity. Though these seem rather low compared to other places I have seen it.

slight frost: 0 to −3.5 °C (32.0 to 25.7 °F)
moderate frost: −3.6 to −6.5 °C (25.6 to 20.3 °F)
severe frost: −6.6 to −11.5 °C (20.2 to 11.3 °F)
very severe frost: below −11.5 °C (11.3 °F)

I though it was
32 - 28 light frost
28 - 26 medium frost
26 - 24 hard frost
24 - ....... hard freeze
Frost can occur when general air temps are above 32F, so the above list is somewhat misleading. The reason for this is that the air radiates heat more slowly than surfaces (including plants), so in certain conditions (mainly clear, calm nights when heat can radiate into the atmosphere more easily) the plant leaves can be colder than the air around it.

Any extended temps below freezing will be an issue for non-cold-hardy plants, especially once you get below 28F, as the water in the plant cells can take a pretty good beating at that point.

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Re: how cold is too cold?

I guess I am not very adventurous or much of a gambler. No tomato or pepper goes outside until all chance of frost is over. Even if tomatoes and peppers get into the ground a week or two earlier than mine, nothing grows until the soil temp and the air temp are above certain points. My later starts catch up pretty quickly and do not have to deal with stress of cool temps. My thoughts and of course I am sticking with them.
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rainbowgardener
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Re: how cold is too cold?

I wasn't worried about frost, we are past frost date, just cold. Like I said tender seedlings can be damaged by too cold, even short of freezing.
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