You read that right ;) Compost socks are basically the long tubes they use around construction sites to prevent soil from eroding into waterways. You can buy the mesh tubes they use (some are sold for gardening) and cut it to length, or construct them from landscape fabric yourself. 

Some potential advantages:

• Compost is cheap, sustainable and can provide adequate fertilizer for the first year or 2.
• Compost can be soggy in plastic containers but the socks act like raised beds. 
• Compost requires less frequent watering than potting mixes.
• A larger plant can be kept happy in the same volume, for me, so far at least.
• Initial growth is comparable to planting in ground.
• Storage for winter is easy, they can be stacked or laid sideways without making a mess. 
• Irrigation is simple: drip tape or soaker hose.
• Easy transplanting, a 15 gallon trench is much easier to dig than a 15 gallon hole, especially if you have rocks.
• You can make your own if you have a sewing machine, it's easy.
• No mixing! Sifting the compost is optional if it has good texture.

• You need to stick cuttings directly into the socks or transplant very small trees. Getting even a 1 gallon into a sock would require a lot of root pruning. 
• Repotting will be complicated... the need could be reduced by allowing roots to grow into the ground though.
• Compost varies in quality, as do the materials used for the socks. Compost can have weed seeds, some landscape fabrics break down quickly in the sun and allow more weeds to grow through. A high quality landscape fabric should be used.
• Filling them is labor intensive.
• They are less durable than other containers
• Small lengths of unfilled mesh tube "silt sock" material are costly to buy, and may require weeding or mulching.
• Compost weighs about twice as much as most potting mixes.
• Direct rooting is less reliable, I've lost something like 10%. Larger cuttings that are callused work better. But then again, they are less likely to collapse from overheating than small containers. 

BRAVO!
That is interesting, as I was thinking of trying something like that myself. My nephew used to work for a company that made and installed those tubes at construction and gas drilling sites. I thought of rooting them first then sticking them sideways in one end of the tube with the trunk sticking out, the roots would then expand down the whole length of a tube and the green shoots would take off vertically(usually, you know how figs sometimes grow...)
My concerns were:
How do I winterize this?
How long will the tubes last, and what do I do when they break down?
When do the roots break thru the fabric?
How quickly would this dry out?
Would I need to stake the trunk for stability coming out of an end of a tube?

Anyway, nice job, well thought out and well documented

I've rooted a few in compost bags before and I agree that it is not reliable. Controlling the water content inside the bag, was probably the main problem.
So how do you water these things?

Great questions Ed! I never thought of sticking them in the end! I got into these to grow strawberries and of course could not resist :) 

I did fine storing the ones I started last year with the others, packed together and stacked 3 high (although that will only work well with single leaders the way I planted them). I plan to try winterizing some in the field this year by tipping them on their sides and pinning the tops flat to the ground and then covering with several layers of agribon and maybe black ground cover over that, will probably try burying some with soil and leaves also. If the trunks were all on one end that might be really helpful to pack them, you could stack them at least 4 high I think.

The landscape fabric I've been using lasts anywhere from one year to 3 or more (basing this on fabric containers I made), mulching will extend the life of the material by blocking the sun. The mesh tubes used on construction sites could be even more durable I think, since the strands are much thicker.
My plan so far for repotting is to set out a larger section of unsewn fabric and then put a layer of compost thick enough to fill the extra space. I will set the tree with the old sock removed in the middle of the rectangle and then roll it over on its side so the edge of the fabric can be pulled up and secured, then, keeping tension on the fabric and pressure on the compost, roll it over to the other side, then top it off and join the sides somehow, stuff the ends and tie them. I'm sure it won't be pretty. I have one seedling sock that split the seam on the side, the roots have grabbed all of the compost really well though so it has been doing fine and I have been putting it off... I think you could do the same if it were coming out the end, no way I can think of to get either into an intact tube though.

I was surprised that the seedlings did not root through the fabric much last year, just very fine roots when on black ground cover, this year I also set some on solid plastic, another layer of landscape fabric, and some just on the soil so I should have a better idea of what they will do. I don't think the mesh tubes will prune the roots at all because the openings are too wide, they will probably run right into the ground and get big, unless therI think, some aggressive weed roots can actually invade them also.

Because there is much more surface area exposed to air they do dry out much faster than a container of comparable volume. But, they catch rain better. The new cuttings were getting a little water daily through the heat wave and they seemed to like it. I lost a bunch of plants in small containers when the power/exhaust fan went out last Sunday morning and I didn't get there to water until after noon, these guys made it through fine though.

Aside from any training I don't think you will need to stake them, they can only tip over to the front or back, not to the sides, any direction the wind blows on a regular container could tip it though, they also flatten out quite a bit and the roots eventually grab.

Very interesting technique, Brant!. So many ways to propagate figs!

Navid.

Thanks for the replies Brent.
How heavy are these when moist?

Great innovation. Going to try to find this sock in my area. I rooted a few large long cuttings horizontally that I ended up putting in long narrow pots.

Great idea and you certainly have good results.

Thanks everyone! I updated the first post with some pictures from today. A little leaf burn did show up on some of them but its nothing compared to the ones in small containers, still waiting to see if some can pull through.
 

Ed, they can be pretty heavy. A 5 ft length of 8" diameter must weigh over 100 lbs. They are pretty easy to drag around though, I might tie a loop on one end to be able to use a long handled hook.

Thanks for your reply and great work.

Great idea on the socks thing. Thanks for sharing.

Picture update in the first post... I did replace a few more that had burned bark from that heat, and a few more that were just not doing much.

Tried Ed's idea (plant into one end) on a seedling, and it went fine. Easy to get a 1 gallon in that way. 

Had some serious flood damage, 7-8 inches of rain in about 2 hours. Almost all look like they will be fine, but a bunch of fruit was submerged in muddy water so I'm worried it will spoil. Updated first post.

Ed- They weigh a ton when soaking wet, had to cut a long one in half to pull it out of the mud, not that the containers were much lighter ;)
  

Hi,
With some wood you could build a "raised table/ raised bed" and put them on that raised bed.
They wouldn't sit in the mud then. They would then suffer more from the sun though ...
Maybe moving them down on the dirt when the weather is dry and then back upon the raised bed when it turns wet ...
Good luck !

For something like salad greens that would be great to keep them clean. This flood was a 100 year event so I should probably not worry too much, lost a couple that got broken up but it doesn't look like any have root rot.

Gave the grouping a little more space. Winner for growth is Kathleen's Black, another one in the back is slightly taller but you get the idea.