I just wrapped the container with a blanket. You think that will help protect it?

I would recommend putting it in an unheated garage to protect it from drying winds if possible. If not, you'll just have to go with what you have.

[Do} you think the cold will effect the Japanese Maple in the large
container? Absolutely - yes. 14*f is the killing low temp guideline for J maples in pots. Would wrapping a garbage bag around the pot help insulate it? Not enough to prevent roots from reaching the killing low temp. In order for insulation to work, it has to be trapping heat from an extraneous source. Example: if you but a plant in a large cooler and put the cooler in a freezer at 0*f, the soil will eventually reach 0* - just not as fast as it would w/o the cooler. If, however, you have a garage that is 0* and you put the plant on the floor and covered it with a cardboard box that has an open bottom, the temperature inside the box could be more than 20* warmer than ambient temps because the box will trap geothermal heat rising through the garage floor. If you lived in an apartment with a cement balcony your best plan would be to put the plant in a box that is open on one side and situate the open side against the building wall to trap heat escaping through the walls.

Sorry if I'm too late.

Al

Strange cause all my 3 gallon and 5 gallon Japanese Maples that were out in the open without protection last year survived the nights we dropped to 14 degrees. They were in peat based potting mix. Maybe that's why they survived?

Yes, younger roots around outer edge are the first part of the plant to go. With the top the last part and the old woody roots in the center intermediate in hardiness. So cold exposure can kill the entire outside of the root system and the tops will still look the same right after a cold episode. Where a more discerning eye might notice a difference is in the tops of plant with partial root loss not growing as much the following season - this is one reason why bonsai are root pruned annually, the reduction in root mass dwarfs the tops.

With one set of tests, while there was some variation within different forms of particular species in which low temperatures were lethal did show a general tendency for plants in pots to be hurt by temperatures about 20 degrees F. above where the same kinds would have been damaged if growing in the ground. So something that might go back at 0 in the ground should be protected from 20 in a container.

Would building up leaves around the container protect it?

Actually, root pruning SIGNIFICANTLY increases wild, rank growth that, from the bonsai practitioners perspective, is something that requires a work-around. We do this by pruning to greatly increase the number of growing points on the plant so the plant's energy is shared between a far greater than normal number of leaves, which also decreases internode length, and by selective defoliation to limit the plants ability to make food. This activity usually occurs mostly in the ramification stages when the trunk is finished and major branches set.

About the A palmatums - since this is the container forum, I assumed we're talking about containerized plants, and 14* is pretty consistently offered as the lowest root temp the trees will tolerate in pots. Of course there is variability based on a significant number of factors, but 14* won't be too far off, and we'd be much better to keep our trees between 32-42* for as much of the winter as possible. Ground temperatures are significantly higher than low ambient air temps. In fact, even in the middle of a bare plowed field, 6" ground temps in Michigan never drop below 25*, even after weeks of sub-zero weather with no snow cover. There are huge parts of Michigan's forested Upper Peninsula that have never seen frost in the ground since records started being kept.

Stuart - building up dry leaves around over-wintering containers can act as protection, especially if you partially bury the trees before stacking the leaves. Make sure the containers are in the shade of a building and out of wind if possible to protect living buds from desiccation. Do watch out for mice, voles, rabbits, deer, and other herbivores that love tender maple shoots. I had an expensive maple (in ground) a couple of years back that was reduced to branches as thick as my thumb and girdled just above the snow line. It did come back from the understock, but the species palmatums are a dime a dozen around here.

Al

I have about 20 Japanese Maples in smaller to medium size pots (2-5 gallon) that have a thick layer of leaves all around them. I am worried about the low temperatures next Thursday thru Saturday which is foretasted to drop down to the low to mid single digits (maybe even below zero Friday night). So I brought all the maples into my unheated garage which stays a good 15 degrees warmer than outside. You think they would have been alright leaving them outside with the leaves surrounding them?

Hard to say, but I'm comfortable with the idea they're better off in the garage. We've had a week's worth of cold flirting with 0* at night, some pretty stiff breezes, too, and water in the the watering cans (attached unheated garage) hasn't frozen yet.

Al

The Japanese Maples were outside when we dropped to 7 degrees. I had leaves all around them and a little bit on top. They have been in the unheated garage since early January because a few days later we dropped down to 4 degrees. I'm worried that my Japanese Maples might be dead from the cold temperature while outside. Do you think that all 15 maples are dead?

You won't know for sure until it becomes time for them to start leafing out........and they don't :-( What you could check for now is how the buds look. If the buds are still plump and of a good color - not shriveled or dried and grayish brown - then chances are good they have survived. Good but not 100%.....there still could be some significant root damage that will take time to be visibly translated to the topgrowth.

Thanks. Do you think the leaves protected them?

gardengal, I brought my container plants (Japanese Maples and conifers) out of my unheated garage because it's almost spring and we expect 45 degree highs during the day.

some of my Japanese Maples in my garage are beginning to bud. What should I do? Should I leave them in the garage or can I bring them outside? The night time temperatures will be as low as 31 degrees in the coming days.

That's kind of what the temps are currently here where I am. They just never got appreciably colder than that .....high 20's was about the lowest.

Since I don't need to worry about single digits or even teens, my trees are outside year round with no protection. They are perfectly happy now under conditions similar to yours and buds are beginning to swell. I would not have any concerns about you bringing yours out, provided you do it gradually (over a couple of days to a week)......and are prepared to take them back into the garage should temperatures plummet.

Thanks for the info.

At what temperature should I bring them into the garage?

Also how would I know if there was any root damage?

If it gets lower than the mid 20's longer than just one or two nites.

Unless you unpot and examine the roots, it may be hard to tell quickly or easily. Generally, if you have root damage or death from cold temperatures, you won't know until it is time for the tree to bud out and it does not. Or it leafs out only partially and sparsely.

Dead or damaged roots will look dark and discolored. And will become mushy and start to smell bad (decaying dead plant material).

One of the Japanese Maples that was in the garage almost has leaves. Should that one be kept in the garage? It's going to be 30 degrees during the next few nights.

I'd start getting it outside gradually. A few (6??) hours during daylight the first day and extending that gradually until it is out all day. Should take about a week or so. And if your temps don't decline much below 30F at night, it can stay out at night as well once it has gotten used to outdoor temps.

Thanks. It's going to be 35 degrees tonight. I brought the maple with leaves into the garage. Should I do the same for the other maples?

So it was already outside? For how long? I would have left it out......35F is not all that cold.

yes, all Japanese Maples that were in the garage are now outside. Its going to be 30 degrees tonight. Should I bring them into the garage?

If in leaf - yes. If not in leaf, protect against actual root temps 25* and below.

Al

Update: I lost one Japanese and another one has has some dead branches. My other Japanese Maples in containers survived and almost have their leaves.