down to 40 F

bower · April 4, 2018

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 · April 4, 2018

they survive it but it causes catfacing on tomatoes

Al@NC · April 4, 2018

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 · April 4, 2018

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

clkeiper · April 4, 2018

Quote:

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.

AlittleSalt · April 4, 2018

Quote:

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.

ddsack · April 4, 2018

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 · April 4, 2018

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.

bower · April 4, 2018

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

Cole_Robbie · April 4, 2018

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.

clkeiper · April 4, 2018

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.

sirtanon · April 4, 2018

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 · April 4, 2018

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

Goodloe · April 4, 2018

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 · April 4, 2018

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.

April 4, 2018	#1
bower Tomatovillian™ Join Date: Feb 2012 Location: Newfoundland, Canada Posts: 6,794	down to 40 F 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!

April 4, 2018	#2
clkeiper Tomatovillian™ Join Date: Nov 2011 Location: ohio Posts: 4,350	they survive it but it causes catfacing on tomatoes __________________ carolyn k

April 4, 2018	#7
ddsack Tomatovillian™ Join Date: Jan 2006 Location: Northern Minnesota - zone 3 Posts: 3,231	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. __________________ Dee **************

April 4, 2018	#11
clkeiper Tomatovillian™ Join Date: Nov 2011 Location: ohio Posts: 4,350	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. __________________ carolyn k

April 4, 2018	#12
sirtanon Tomatovillian™ Join Date: Apr 2006 Location: Phoenix, AZ (zone 9b) Posts: 796	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. __________________ I could sail by on the winds of silence, and maybe they won't notice... but this time I think it would be better if I swim..

April 4, 2018	#3
Al@NC Tomatovillian™ Join Date: Jun 2012 Location: Vernon, BC Posts: 720	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

April 4, 2018	#4
AlittleSalt BANNED FOR LIFE Join Date: May 2014 Posts: 13,333	It was 40F here this morning. The plants look fine. Mine are a long way from producing tomatoes.

April 4, 2018	#8
My Foot Smells Tomatovillian™ Join Date: Jun 2015 Location: Pulaski County, Arkansas Posts: 1,239	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.

April 4, 2018	#10
Cole_Robbie Tomatovillian™ Join Date: Jun 2012 Location: Illinois, zone 6 Posts: 8,407	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.

April 4, 2018	#14
Goodloe Tomatovillian™ Join Date: Jan 2018 Location: Steens, MS 8a Posts: 410	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? __________________ ~Jon~ Downheah, Mississippi

April 4, 2018	#15
MickyT Tomatovillian™ Join Date: Dec 2017 Location: North Vancouver, BC, Canada Posts: 46	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.