Snow In Arizona

[AaronThomas]

LOL... hmmm well, haven't had to deal with this since I moved to Tucson but we've gone from weeks of 60 and 70 degree weather to 34 and snowing. All my Elms have started to bud... I've brought them closer to the sliding door under an over hang and was planing on covering them tonight to protect from any frost. Should I just bring them to the garage again? Going to be have cooler temps in the low 30s for the next few nights but 60s during the days. Strange place this desert!

 

[jkd2572]

I would put them back into the garage until the temps are above 40 if they are already leafing out. I have had to do the same thing this year. You can get frosts that can kill those new leaves in any temps in the thirties. I leave the garage light on to at least give the new leaves some light.

 

[AaronThomas]

Thanks so much! Have T8 lights on work bench so Ive got that going for me!

 

[jk_lewis]

Leave them be. They're elms and are tough. You'd have to have had hours at mid 20 F temps to do any damage.

 

[Poink88]

Leave them be. They're elms and are tough. You'd have to have had hours at mid 20 F temps to do any damage.

He is right. I never bring my elms in...granted our temps also do not dip too much.

 

[rockm]

If your elms have new leaves, they cannot withstand freezing temperatures. You risk significant damage to the entire plant if you ignore things. You will definitely get freeze damage on the new leaves, if the soil freezes, you risk killing the tree. Bring them into the garage.

Deciduous trees lose almost ALL of their ability to withstand freezing once leaves emerge. That's the way it works. It all depends on how low and for how long the temperatures stay below freezing. The smaller the pot, the more likely you will have frozen soil. The more exposure the plant has to the lowest temperatures, the greater the danger.

If this were happening here in Va. (and it does all the time come March and April) I bring plants inside until temperatures recover above 38 or so. This usually means bringing trees inside for the night and putting them back out in the late morning, then repeating the process until nighttime temps remain RELIABLY above freezing...

It freezes in the desert and it snows in Arizona. I used to live in Scottsdale. It snowed once in a while and got cold too. Tuscon is high desert and tends to get more snow, than Phoenix, though. The arid desert air can't hold onto heat and temps can drop steeply once the sun goes down in the wintertime.

 

[Poink88]

Even though he is not getting anything below 33*F ?

 

[rockm]

"Even though he is not getting anything below 33*F "

Can you guarantee he won't get anything below that?

I bring stuff in in March and April when the forecast says temps may be around 35 or so. Localized freezing is likely when the forecast skirts the freezing mark so closely. Ignoring that because the weatherman said it was only going to get to 35 is a possible death sentence for your trees.

The "oh, it's only going to be 35" skips past the reality of microclimate, terrain (cold air flows downhill--if you're at the bottom of an incline or hill, you will be colder, sometimes drastically colder than the surrounding area) and error. Yeah, the forecast is ALWAYS right...

Also, given the dry air in Tucson, temps can drop very fast. I've been there when it snowed and froze. Sunny afternoon, freeze by midnight...

 

[Poink88]

Can you guarantee he won't get anything below that?

You know no one can.

Re: your argument, the same is true to counter it. We do not know if his microclimate is consistently higher than the forecast (like my area since I am on the higher side of a hill).

33*F in my limited experience is safe for my elm...even if it goes 5 degrees lower. Maybe I am mistaken?

 

[rockm]

"Re: your argument, the same is true to counter it. We do not know if his microclimate is consistently higher than the forecast (like my area since I am on the higher side of a hill)."

Oh fer heaven's sake. No, can't say that he has a microclimate, but I do know how to deal with frost and freezes. Leaving the trees out unprotected in a forecast that has temps skirting freezing is dangerous for trees. At the least, he will get frost burn on new leaves, as temps bottom out just before dawn. I've had that happen on my trees when the actual air temperature didn't drop below 34. He may not, but WHY TAKE THE CHANCE IF HE DOESN'T HAVE TO?

"33*F in my limited experience is safe for my elm...even if it goes 5 degrees lower. Maybe I am mistaken? "

Given your extremely limited experience of a SINGLE winter, yeah you are gravely mistaken.

 

[Poink88]

Given your extremely limited experience of a SINGLE winter, yeah you are gravely mistaken.

Yeah but I am surrounded by millions of elms for years...all go through freezing temps with their little leaves around this year but cannot move because they are on the ground. All seems fine.

BUT as usual you are NEVER (did I say NEVER?) mistaken so thank you for gracing me/us with your unending wisdom.

 

[jkd2572]

Even though he is not getting anything below 33*F ?

Frost can happen to almost 40 degrees. Have you ever seen frost on your cars windows when its 38 degrees. I have.

 

[rockm]

Dude,

Comparing trees in the ground and trees in pots is extremely shaky ground.

Roots aren't protected in pots. Bonsai are more exposed that trees in the ground. Forests and groups of trees in the landscape are not bonsai. Anyway, even in-ground trees have problems after a frost when just coming into leaf. Here in Va., apple growers face all kind of problems with late frosts. Trees drop blossoms, some are defoliated it it gets cold enough. IN a forest, trees on the outer edges and leaves at the very tops experience radiational cooling and do get nipped, blacked foliage is the result. Next late frost you get, take a closer look...

As for me being right all the time, I'm not the one posting about overwintering, frost and freezes from an area that doesn't really get them. I'm hardly right all the time, or even most of the time, but at least I have some experience with what I'm talking about.

 

[jkd2572]

Good grief. If you can bring them in bring them in. No need to babble on about it. They will be better for it and you might get some exercise.

 

[coh]

Tough call. My experience is that the new growth on most hardy plants can survive a minor frost/freeze. By that I mean if the temp dips to 32 (or even 30 or a bit lower) for a couple of hours, there shouldn't be any problems. After all, in most of the temperate regions, spring typically brings with it a few late frosts/freezes, and the plants have adapted to handle that. As for the roots...I think the chance that a pot of damp soil will completely freeze in an hour or two is pretty small. Smaller pots would be at greater risk, obviously.

Since you're new to the area it might be smart to bring at least some of the plants in, until you learn more about your specific microclimate. It's possible you live in a colder spot (as compared to city, for instance). Or wait until as late as possible and check the actual temperature and make a judgement at that point. I'll often do that. For instance, if it's clear and calm and already 33 deg at 11 pm, chances are good that the temperature will drop several more degrees. If it's cloudy and/or windy, that is less likely.

Chris

 

[jkd2572]

More about frost and why the measured forecast temps don't always tell the whole story.

Because cold air is more dense than warm air, in calm weather cold air pools at ground level. This is known as surface temperature inversion. It explains why frost is more common and extensive in low-lying areas. Areas where frost forms due to cold air trapped against the ground or against a solid barrier such as a wall are known as "frost pockets".

 

[Dav4]

More about frost and why the measured forecast temps don't always tell the whole story.

Because cold air is more dense than warm air, in calm weather cold air pools at ground level. This is known as surface temperature inversion. It explains why frost is more common and extensive in low-lying areas. Areas where frost forms due to cold air trapped against the ground or against a solid barrier such as a wall are known as "frost pockets".

One of the very few good things about living on a hill...

 

[coh]

Chances are that the original posters plan of putting the trees next to the house, under a roof will be enough protection. That will markedly lower the chance of radiative frost(*). I would recommend placing a min/max thermometer with the plants so that the actual low temperature can be measured. There are some remote-reading thermometers that have an alarm feature, the alarm will sound at either a pre-set temperature (usually 32 F) or a user-specified temperature.

Of course, if we're only talking about a "few" plants, then just move them into the garage for the night...you'll sleep a lot better.

(*) radiative frost - occurs on clear, calm nights when the ground rapidly loses heat to the air. Ground temperature can become significantly lower than the temperature at the "typical" measurement height (6'). This is why you sometimes see frost on the ground (or on a car roof) when the air temperature is above freezing.

Chris

 

[AaronThomas]

I leave for a few hours and look what happens! Originally I did put the trees by the glass door under the over hang for some radiant heat from the house and was going to cover with pillow cases to protect from frost. I only have 6 trees outside at the moment so yes... I will sleep better now that I put them in the garage... I will of course bring them back outside in the morning. I figure since some are in leaf and others are just starting to bud.. why risk it. Frost here (and I assume most places) can form only when the temp drops to around 41 at night. We live on a golf course and wake up to white fairways regularly this time of year. My Elms don't usually start budding till the very end of Feb but due to the beautiful weather lately they popped.

I appears that the cold temps in the 30's are only going to last a week or so... "THEY" are predicting the evening temps to be in the 40's.... but what do "THEY" know!!!

Thank you all again for your responses!!!!

 

[AaronThomas]

WOW.... yeah will sleep much better. Wasn't expecting this! 2" and counting.....