What is your intended purpose of the pot-in-pot application and how are you going about implementing it?

Al

just reading on this post about putting a smaller pot into a bigger pot mulching and wintering it over out side. Have two junipers. Intended to keep them outside on a covered patio,small bonsai(starters). Any other suggestions? Thanks in advance

You'll get no true insulative value from utilizing the pot-in-pot technique per se. It's possible, in some circumstances that it may work against you to actually lower pot temps during extreme cold. How you implement has some influence over whether or not it offers protection, how much it offers, or whether it actually is counter-productive. It primarily serves as a buffer that affects the speed of the change of soil temperatures, but has very little influence on the high or low root temperatures that govern how the plant reacts to chill.

For suggestions - need to know more about how enclosed the patio is, what elevation it's on (what direction it faces), on a slab(?), what zone you're in and either the species of juniper(s) or to what USDA zone they are rated as hardy.

Al

Al, I'm in zone 5. NE Pa. Ihave 2 dwarf Japanese junipers. My patio faces west it is covered not enclosed. Since I'm new to the art of bonsai I have been reading through the forum(s) and also on the Internet. This method caught my eye,but apparently not good. Also have an unheated shed. Maybe that's a better place to winter them. And suggestions would be helpful thanks

How about an attached, unheated garage. I over-winter around 175 temperate conifers and deciduous plants in my garage, and junipers are well-represented among them. Alternately, you could bury the plants, pots & all, against the north side of a heated building out of the wind, or just bury pot & all in the garden & mulch well, though the later 2 options leave you somewhat vulnerable to the possibility of rodent damage, mainly voles & rabbits.

Al

Don't know about 'voles' but for the mulch method most rodents and other pests can be handled by mixing kennel bedding into the mulch and spreading some mothballs around. As they dissolve just spread some more around.

Bob

I wouldn't put much faith in moth balls as a deterrent. Unusual odors, like those generated by a long list of home remedies (moth balls, bleach, ammonia, peppermint oil, .......) commonly cited as effective at keeping mice/rats/voles/rabbits away are somewhere near totally ineffectual at convincing rodentia to vacate the premises. This would be especially true in unenclosed areas where the volatile chemicals we depend on as would-be deterrents are wafted away on the first breeze. I always shake my head when I hear the suggestion that bars of Irish Spring soap hung on the branches of shrubs or nylon hose stuffed with dog or human hair clippings will repel deer and rabbits, or that fox urine will keep various varieties of vermin away. It just doesn't work.

Case in point: I have a friend who built a pit in which to over-winter his bonsai trees. The pit was mostly covered with treated plywood that was screwed down, but the ends were covered with expanded metal grids to allow air to flow through (to prevent fungal infection). He surmised it was a curious coon or skunk that pried up a corner of one of the grids and allowed access by who knows what (mice/rats/voles/chipmunks? - we're sure it wasn't beavers), ;-) leaving him with a considerable amount of damage to a significant number of his trees - this because he didn't want to use a rodenticide instead of the 5 lbs of mothballs he'd scattered everywhere.

I have some 'Yatsabusa' tridents in the ground that had been particularly attractive to voles in the past. I built a 'vole medicine dispenser' from PVC pipe & fittings,
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filled it with about a pound of Ramik rodenticide balls, and put it under the trees. I also scattered a box of mothballs around the dispenser and then mulched heavily with leaves (because the trees are only marginally hardy here). In the spring when I raked the leaves away, there was no mouse/vole damage, the dispenser was completely empty, and the mothballs had lost about 3/4 of their original size, illustrating that they are simply ineffective.

I'd hate to see anyone depend on their (mothball's)effectiveness & end up with damaged or unsalvageable trees.

Al

Right Al, don't put any faith in anything that anyone else, except you, says.