When to start leaving plants outdoors?

digger714

Shohin
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I have several plants that have started budding, and pushing new leaves. Most of these are starter plants. so no more that 1 year old. When is it safe to leave out at night? the temps here are getting into the low to mid 60's this week, but getting down to 40 at night? is that warm enough to leave outdoors. I am currently taking out during the day, and putting in at night since it has been getting down to freezing. They are not calling for anything below 39 or so but in the high 50's lower 60's in the day. Thanks for any advice.
 

Brian Van Fleet

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Depends on the species and their indigenous zones; share what you have and you'll get more specifics.

A good rule of thumb is that tropical trees can come out when night temperatures are consistently above 50, all others when nights are consistently above freezing.
 

digger714

Shohin
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I have several types of trees that i am starting. i have trident maples, quince, hornbeam, cotoneasters, gingko, birch, persimmon, crabapple. elms, then junipers, black pines- 1 year old seedlings, and cuttings, white pines. I just wasnt sure if above freezing is warm enough. We are suppose to have lows of only 38 - 40 this week, and next. Thanks for the info.
 

Brian Van Fleet

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All very hardy in NC...good selection too! You should be fine...Enjoy!
 

buddhamonk

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even below freezing should be fine as long as they're protected from dry wind
 

rockm

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Below freezing is NOT OK for leafed out deciduous trees--even if sheltered from the wind.

This is the most dangerous time of year for deciduous bonsai. Trees that have begun to push new leaves HAVE LOST ALL THEIR ABILITY TO WITHSTAND FREEZING TEMPERATURES. Once leaf edges are visible on buds, deciduous trees have exited dormancy and lose their winter hardness.

That means if temperatures around the roots drop below freezing, roots will be killed--which can result in the loss of the tree, as it will have expended most of its stored energy pushing new growth... The smaller the pot, the greater the danger to the tree in it. Smaller pots have less soil volume and freeze more quickly than larger ones.

Freezing temperatures around new leaves will freeze tender new cells completely, turning newly emerged leaves to black mush.

The best thing to do now --in areas that haven't seen their last frost date pass--is to be VERY vigilant about nighttime temperatures. A rule of thumb--if the temp is forecast to drop to 35-38--bring the plant inside the house for the night--even if you have 30 trees. Find a temporary place for them.

Also think about when you put them back outside (hopefully it won't be more than a couple of days). Placing trees back out in the morning before the sun has had a chance to warm things up, could expose them to freezing also...
 

jk_lewis

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Below freezing is NOT OK for leafed out deciduous trees--even if sheltered from the wind.

Very true. I disagree, though, about freezing damaging the roots -- newly cut or not. I usually have much of my repotting done before trees leaf out, and have frequently had these bare trees get frozen in a day or so afterward. I've not had a problem with any temperate-zone deciduous trees.
 

rockm

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"I usually have much of my repotting done before trees leaf out, and have frequently had these bare trees get frozen in a day or so afterward. I've not had a problem with any temperate-zone deciduous trees."

Repotting should be complete before any trees leaf out. Once leaves are showing, it's too late to repot--at least until leaves harden off in June (for some species).

I have had problems with frozen cut roots. They tend to die back from the cut site, instead of producing new roots there. That can lead to all out rot of that cut root, as decay sets in on the dead part. It's avoidable, just by either mulching the newly repotted (and leafless) tree back into the garden bed, or by bringing it inside temporarily.
 

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