2 months ago I took 10 suckers from an old fig tree root, and planted these out. The smaller ones are doing just fine, the bigger ones however.... 5 of the plants are about 4-5 feet tall and had roots about 2 feet long. They keep on trying to set new leaves, but before unfolding, the leaves start to wilt at the tip, and in a couple of days these wilt into a hard little dried leave shell. When I peel the dead leaf off, a new fresh and green leaf is underneath. The cycle then continues. It has been 2 months now, the plants keeps on producing new leaves, but none of these unfolds. Any ideas as to what might be wrong?

Yes what's wrong is those shoots don't have enough active roots to support the new leaves. So the leaf wilts and another tries to grow. There are enough roots to keep the shoot alive but not enough to support new growth.

What I'd do is cut the shoot way back and let it go dormant. Then next spring it will probably grow enough new roots to support new leaves.

If you are in the southern hemisphere meaning it's spring I'd still cut the top way back. It needs time to grow roots before it can grow leaves just as a cutting does.

Thanks for your quick reply Fignutty. I am in the southern hemisphere (Melbourne, Australia) and it's late spring here at the moment. I did consider cutting them back before I planted them out, but decided against it, as my garden is quite bare. I thought I'd save a season or two of growth by leaving the suckers tall. Do you reckon I'd kill them by leaving them as is? I'll cut them back if that's what it'll take to save them. Once again thank you for your swift response. 

I would also recommend cutting them back, if its late spring there then they should have plenty of time to put out new growth/roots, I have a similar problem with cuttings where they put too much vegetation out before the roots are fully developed and the bud gradually withers away

Hi,
I wouldn't cut them back.
At this point they may not have enough roots, but you can help that with watering more.
Water them more (every day 1 gallon per tree - since they are in ground) so that the roots they have can catch enough water. Give them some fertilizer to help the roots grow faster.
At this point, whether you cut or not won't make a difference. They shall make it or crumble.
So if they shall escape that situation, it would be better to have them bigger.
If they are in full sun try to provide them some shade for a month and then let them do what they can.
You could plant lettuces around the trees to keep their feet wet.

Shade and watering are good ideas. I assumed adequate watering. But that might not be a good assumption.

On the other hand cutting back the top is a good idea if the main consideration is saving the plant. That will force new growth to come from dormant buds. That means any attempt at pushing new leaves will be delayed by a month or so. That delay will allow time for establishment of new active roots. There is no downside to cutting back 4-5ft tall suckers that lack adequate roots. The remaining stem will push new growth in good time. You won't kill the remaining plant.

If the main consideration is instant 4-5ft tall growth, keep the top, shade and water.

The cut back plant will grow much faster than not cut back. By fall top size should be about equal. This is the same thing as planting a bare root fruit tree. That's basically what has been done with these fig suckers.

Thank you all very much for your help and good suggestions. I must admit that I haven't been watering at all: We've had a very wet spring so far, so much so that I'd started to worry about the roots rotting. Also, I'm a bit reluctant with watering after I killed off 25 little cut-offs a couple of years ago (I basically drowned them, and it still haunts me to this day). There's 5 big plants in all, so what I'll probably do is cut back the 2 worst affected, and moderately water 3 or 4 of them. I just noticed this morning that there's a bit of cob web action going on in between some of the shoots. Could it be some bug/mite that's responsible? I'll try and grab some photos later today, if that'd be of any use.