I recently had to do a radical, root-prune and total repotting of some small 4 ft.  fig trees.  The trunks are about 1-1/2"  - 2-1/2" in diameter.  Five years ago they were rooted twigs growing in one container which was placed on the lawn.  Well....the trees grew, I neglected them, and they busted through the bottom of the original container and rooted into the ground,where they continued to grow until a couple of weeks ago.

So that I could containerize these individual trees, I had to dig them out, which entailed a root-chop, and then planted them into  large, containers.  Some of the root systems on two of the trees seemed to be pretty sparse, but the trees are starting to show signs of  life...I think.  The terminal buds are still green, and the stems branches show green when scraped with my thumbnail.

Q U E S T I O N :

Is there an easy way to keep the soil in a 18 gallon container warm so that the root system could regenerate faster?  After the root-chop the night temps. went into the high 30s and 40s.  - so the soil around the chopped roots stayed very cold.  This made me nervous.  Cold, damp medium = rotting roots.  I'm using a quick-draining mix, but it still holds moisture.  The small trees at this point, are really just giant, rooted-cuttings.

I was thinking of something like a small, 25 watt light bulb buried in, or placed under the container, plugged in of course, that would keep the soil heated as temps. drop.  This set-up would just be temporary, until soil temps. stayed  continuously warm as the season turned into Summer. 

Should I have my heat examined?  Any merit to this idea?  Opinions please.

Frank

If you can get the pot off the ground so that you have room for the light bulb underneath the pot and space  for air movement that should work. then wrap, insulate the pot right to the ground somehow to keep the heat in.

Be patient - try to put yourself on tree time - they move slowly. Roots grow as long as the soil is above freezing. There is an advantage in postponing leaf out after a radical root pruning because it allows the root system to regenerate so it's better able to support the canopy when it comes. If you warm the soil, you're going to have a flush of top growth, too - that's how it works - soil temps above about 45* stimulate budbreak. When that occurs, it's better to have a strong root system in place, instead of the tree having to play catch-up.

Al 

BTW - for cuttings:

Bottom heat is good up to soil temps of about 65-70*. Above that, don't use bottom heat. It's best if ambient temps are cooler (10* or more) than soil temperature during the rooting process. As soon as you have evidence of roots, turn the bottom heat off. At that point, roots should be cooler than ambient temps (accomplished naturally through evaporative cooling as the soil solution evaporates) for best growth/vitality.

Al

Thank-you for putting my mind at ease. 

I broke out into a cold sweat this past week because the weather, and night temps. were cold and chilly, and I convinced myself that the newly pruned roots were morphing into a soggy mass of putrid rot.  I'm ashamed to admit this publicly but I was sick to my stomach at the thought of losing some of my fig trees.  Is this a normal response?  Is there a pill I could take to prevent this anxiety attack?  I've become some kind of  "Fig Psychotic".  This "fig-thing" has to stop!

Thanks, for the slap-to-the-face, and for the quick, technical explanations essentially saying that the trees are OK.  I also like the heating suggestions, which will/might be used sometime in my future. (hblta and Al T.)

OK....I feel better.

Frank, from da- Bronx

Excellent info on heat & rooting that got nailed down. This year is the 1st time I have used a heat mat and I noticed if I moved my newly planted cuttings that are further away like 4" above heat mat, the cutting roots seems to like it. Compared to those like 1" above the heat mat. Thanks Al.

Frank, I can understand feeling uneasy on the possibility of losing a tree. I have been rooting trees and some die. I am starting be OK if a cutting has mold or dies and I have to throw it away. I compensate the loss by looking for more cuttings in the small communities here in California. I am still in the learning stage and don't beat myself up.......Take Care !!!!