down to 40 F

[bower]

Just looking for a reality check, from everyone, everywhere.
Have you seen any harm from a night time low of 40 F, on
(a) seedlings in pots
(b) plants in the ground or (full size) containers

assuming there is some protection, either a greenhouse or other temporary shelter.

I know a 40 F night is not ideal. I just want to know your experience, how well your plants survived it. TIA!

[clkeiper]

they survive it but it causes catfacing on tomatoes

[Al@NC]

If it's seedlings then hopefully your medium is on the dry side because it can cause them to dampen off as I found out recently...

Al

[AlittleSalt]

It was 40F here this morning. The plants look fine. Mine are a long way from producing tomatoes.

[ddsack]

I can get occasional stretches of nights in the low 40F's and lower in early June after plant out. No harm done when it warms up during the day to the 60's or 70's. As long as they don't actually freeze and get sun and heat during the day, they grow just fine.

For younger seedlings, my night time greenhouse temps (with heater) can drop to 36-38F if the outside night temps get to 25F. The seedlings rebound nicely in the heat of the day. Again, as long as they don't actually freeze, I don't see a need to worry. Now, if you have low night temps along with stretches of cloudy weather with daytime highs only in the 50's, that would set growth back.

[My Foot Smells]

How can it frost when the temperature is above freezing?


(Note that the water vapor goes directly from gas to ice. Therefore, frost is not frozen dew.) Thus, if the temperature on the ground or an object such as a bush or a car windshield near the ground falls below the frost point, frost crystals may form. But the measured "surface temperature" may still be above freezing.

*******

I always get confused about frost & freeze. Still am. But 40 should be fine for all involved - unless you live in a cold pocket.

I remember where the Russians did a number on tom plants to see how cold they could take, kind of a botanical gitmo. Seems like 28F was a big # if my recall is correct.

[clkeiper]

Originally Posted by AlittleSalt

It was 40F here this morning. The plants look fine. Mine are a long way from producing tomatoes.

they may be a long way from seeing any blossoms but deep within the plant that blossom is already forming. it can damage them.

I tend to go through and pinch off any of the first tomatoes that look funky as soon as I see anything "off". I suppose anyone wanting the first tomato of the season would leave it but I don't. I want to sell mine.

[bower]

This is great, lots of very important points, keep em comin!

Checklist so far:
- bad for beef shapes (+ early fruit may be wasted)
- safer if soil is dry
- well tolerated if daytime highs are 60-70 F
- don't forget risk of low day temps (yup Dee this is a big one for me, if the sun doesn't shine!)
- actual frost crystals are the damaging thing at the low point

[clkeiper]

get a supply of milk jugs or "hotcaps" to cover them if the night(s) are getting that low. leave the cap off the jug and cut off the bottom and cover them if they are small enough plants. we aren't even seeing 40 as a high here. such a bummer.

[Cole_Robbie]

Remember, 40 and clear can be 35 or so in a plastic house.

Six-pack plants get it the worst. They will turn yellow and purple in the 30's. Potting up to a larger container makes a big difference.

Daryll - aka fusionpower - has posted about how getting the plants hot in the day time will make them recover better from a previous cold night. I don't think he theorized about the causes for that, but I think it is bacterial in nature. The warm temps help your good bacteria grow back without dying off. That's also part of why a larger container helps, too. I can see a drastic difference in 4" pots versus 48-cell web trays.

[sirtanon]

This past winter, I had tomato plants in the ground, as well as in pots, in my backyard when the temperature got down to 33, without covering them, and they did fine. Heck, the temps got down to 27, and they were covered with some heat buffers placed around them, and they still did fine.

IMHO, 40 degrees F is a cake walk for most tomato plants.

[bower]

Container size - I did not know that. Very helpful to know!!

[Goodloe]

I'm concerned about temps the next few days, myself. Supposed to be about 36 tomorrow morning...32 Saturday morning. I've got 15 tomato plants in the ground, and they have been hardened off to about 42, so I don't think 36 will be a problem. Not so sure about the 32, though.... Any thoughts?

[MickyT]

I'm playing around with a few plants this year just to see what happens and to compare early and later plantings. I put out 6 week old transplants on March 15 into my unheated high tunnels. Some in 12 gallon grow bags and some into raised beds covered by the tunnel. The day temps have been 45 - 55 and night temps 36 - 42 since then. The tomatoes in raised beds showed severe cold stress and I ended up pulling them all. However, the plants in grow bags are faring better. You can definitely tell they were stressed with yellow leaves, it looks like they really struggled to uptake nutrients. But recently they are showing positive signs - the new growth is nice and green and one of them is starting to show tiny flowers forming at the growing tip (Stupice). The other varieties that look to be surviving and putting out nice new growth are Oregon Spring and Jaune Flamme.

[AlittleSalt]

Originally Posted by clkeiper

they may be a long way from seeing any blossoms but deep within the plant that blossom is already forming. it can damage them.

I tend to go through and pinch off any of the first tomatoes that look funky as soon as I see anything "off". I suppose anyone wanting the first tomato of the season would leave it but I don't. I want to sell mine.

I'm the same when it comes to removing odd looking tomatoes. Thank you for the advice and knowledge.

I do have some seedlings, but I brought those inside before the cold front hit yesterday. It's a good thing I did because there was some dime sized hail and high wind gusts of near 40mph.