Hi Damian,
Ok, I'll bite!
Now bear in mind that I'm living in Cape Town, South Africa .....
When to dig.
Here we have two growing seasons for these olives. One is now, for about 2 months, and the second starts in September'ish. So, what you need to do if you want to be successful in collecting olives is determine when your growing seasons are there. It's not always just summer and winter. Our olives shut down in the heat of summer, and grow again now in autumn. Ideally, you want to dig 'em just as the dormant season stops and growth begins. This is more important for trees that you take the roots off, and those with less stored energy (smaller trees). Telling when this period is is simple. Just watch for new buds popping on your trees in the wild. As soon as you see this, mark it on the calendar and then dig. The following year, dig two weeks earlier. Then, watch again for the spring growth spurt, and do the same in terms of timing.
Digging.
Identify your tree. If it is small, then keep as much root as possible when digging. If it is larger, then you can just saw it off at the base and grow it like a cutting. If you do this, you must have a good idea of your design so that you can cut in the correct place. Ideally this should be done at the widest part of the root bole, but it will depend on what you envisage as a planting angle for the tree.
Once you dig, plant them in course river sand (2mm particle size), or some thing similar. I have used 3 to 5mm sandstone gravel mixed with milled pine bark of a similar size with good success. The key here is to have a mix that allows the humidity internally to remain high, but still allowing air into the mix. Importantly as well the mix must not be too fine otherwise rot can set into your root system. So, find a mix that is free draining, and yet keeps good humidity. It must not dry out in there. If you chainsaw the base, I like to cut (with a sharp knife) a 45 degree edge on the cambium layer at the cut. This has the effect of maximising cambium for root growth. (at least that's what I think!) I then paint the exposed cambium layer with a rooting hormone. Other people use honey etc. I also water with what I call willow water (water in which a willow tree is growing), which has salacilic (spelling?) acid which leeches from the willow roots into the water. This acid is a root growth enhancer. Some folks choose to soak their trees in a concoction of similar type stuff. Seasol, Asprin, etc etc. you can soak for a few days. I would not soak for longer than that as a rule, but as an experiment I've had an olive here in the shade at home growing quite happily without roots for about 5 months now in the same tub of water as a willow cutting!!
Then the waiting game.
I've had trees sprout in 4 weeks, and I've had one that took 22 months!! Be patient. If it's a good tree, it's worth it! You know it is still alive if you scratch to the cambium and it is still green. Remember, throughout this period you need to keep the soil just right in terms of humidity! Finally you will see swelling at nodes. This swelling can be up to a few mm in height and then the bark cracks and out poke the buds! Hallelujah! If you are lucky, the tree will sprout everywhere! If you are not so lucky, it will sprout all over the top, and nowhere else, and if you are totally unlucky, it will sprout only from the base. I've had varying results. Tip. Identify which you think will be be back of the tree, and face this side to the best sun. I've found that my olives seem to bud more on the side with the best sun, and that's best if this is the back of the tree to give branch options for a final design, as we normally want less branching in front and more at the back?
Finally.
Now the Importent bit. Once it is growing, LEAVE IT ALONE FOR A FEW YEARS!!!! There is a strong opinion here that by allowing the tree to just grow unchecked, you allow the roots and saplines to establish and recover from the dig. This is critical to a healthy tree down the line. If you don't do this, we believe that it leads to die-back 5 to 10 years later of branches that just fail to thrive as we love them to death. In bonsai I think we have a habit of not giving our trees time to recover in amongst the training, the nipping, pinching, pruning, etc etc, so it's imperative to start with a tree that has a healthy system.
And now I'm tired! Here are few links to my craziness!
viewtopic.php?f=130&t=15489
viewtopic.php?f=130&t=11778&start=15
viewtopic.php?f=9&t=9058
Have fun and fire away with da questions!
Andrew