Ask Mr. Smarty Plants

Since you did not specify the species of oak tree you are considering transplanting, we have chosen Quercus agrifolia (California live oak) as an example. It is the common oak of the Southern California coast and foothills. From our webpage on this tree, you will learn that it needs a well-drained soil, which a compacted soil is not. An added complication is that oaks have long taproots, sometimes growing 5 feet of taproot in one year from sprouting. The best and fastest-growing oaks are grown in place, starting exactly where they end up. 

However, if you are willing to put in some work and experiment, perhaps some small trees can be transplanted with a good survival rate. They should not be planted until the coolest time of the year, probably December or January in Southern California. So, start now doing something about the compacted soil you are planning to put those trees into. You're going to need to get some organic materials mixed into the soil to improve the drainage. And you're going to need a hole considerably larger than the root ball of the oak you are transplanting. Select prospective sites for your little oaks, and incorporate compost, leaf mould or other materials into the native soil of the hole. It will have a few months to continue to decompose, improving the texture and drainage of that soil. And choose your sites with an eye to the mature tree. Planting any tree near pavement, sidewalks or even foundations is a mistake. Even trees with taproots have lateral roots growing out to twice the width of the dripline of the tree. 

When planting time comes, first dig your hole, in the previously amended soil. Then dig as large a root ball as you can manage, transplanting one tree at a time. Leave the root balls out of the ground as little time as possible. Drying of the roots can be fatal. Get it into the ground, and gently return the better-draining soil you have created to the hole around the roots. Stick a hose down into the soil and let it drip slowly until water appears on the surface. Do this two or three times a week until the tree seems well established. If the water remains on the soil more than a half hour or so, it is still draining poorly. Trees cannot survive with too much water around their roots; they will drown. You may mulch the roots with a shredded hardwood bark to shade and protect them, as well as hold moisture in the soil. Do not mound this mulch up again the trunk of the tree, as that will promote mold. The mulch will continue to decompose and, again, contribute to the drainage around the roots. 

Quercus agrifolia

Quercus agrifolia