Yes, you can do that, but I would wait until spring. I assume that by "letting the trees get larger" you mean keeping them containerized for another growing season? Most trees, especially deciduous trees, don't appreciate their roots being tampered with when they're in leaf. Though you could probably go ahead with what you are planning, it's likely the trees will "sulk" a little if you do it now, which might have an effect on the amount of energy the tree will be able to store for winter, making for a weaker spring growth push. Growth (of leaves & branch extension) on your trees has largely stopped for this growth cycle & the tree is concentrating on making buds & storing energy for next year.

Go ahead with your plan next spring just before buds move, or at the very onset of budswell (at latest) for best results. After leaves fall would also be an acceptable time to plant. As you go into your second(?) year with the same soil, be careful about watering habits. As soil breaks down over time, it holds more water & less air. Be sure to take that into account.

Al

What is possible to do in autumn is prepare the sites where you plan to plant your trees.

When you take them out of the containers the roots may need spreading out so prepare for this by digging over, adding compost and any fertiliser over an area bigger than you think you'll need just from the container size. Maybe around a square yard across and thirty inches (give or take) deep.

I've heard there has been a period of drought in your area this season. Opening up the ground will let the rain water penetrate, too.

If you garden on a strong clay soil it is better to make the planting hole irregular in shape, In clay a round hole forms a 'container' around the root ball and the roots start to circle instead of forage

Thank you very much! This info is exactly what I needed.

The BEST time to plant trees and shrubs here in TX is the fall. This gives their roots time to grow with out any heat stress. And the roots might freeze in a 5 gallon container if we have a hard freeze. Also the roots will start growing in a circle around the pots.
I, too, have had to contend with the deer, for 8 years. I make a fence cage to encircle the trees. I made the mistake of thinking the were safe once they were taller than the deer could reach, Wrong!! Then the bucks came by to polish their antlers. Your trees will have to be good size, to keep them from killing them by rubbing the bark off, before you can remove the cages.

I would be reluctant to offer overall advice on the BEST time to plant a tree out, choosing to base the advice on the tree, zone, soil, rainfall, temperature pattern, ad infinitum, instead of a general rule; but, I believe Sarah was referring to potting up, & the best time to undertake that is in spring, immediately before or at the very onset of bud movement.

Al

Sarah,

Where do you live in Texas? Growing in Texas can vary greatly with hardiness zones being from 6 to 10. The following can give you some information, but like I mention at the end of this post, give your county extension office a call and ask for advice.

Tree Planting in Austin,Texas states:

Winter is one of the best times to plant a tree. Many excellent varieties are available at your local nursery, with some of the best trees available in the winter. Your new tree will use the winter dormant season to establish new roots. When spring arrives, your tree will be on its way to providing shade for generations to come.

Stephenville Extension Office states:

At any time of the year you can plant shrubs, trees, perennial flowers, herbs, and ground covers which have been growing in containers. If you are planting during the winter or late fall, they must be plants which are reliably winter hardy in your area. They should also be "hardened off", or gradually acclimatized. This means that they should not come from a warm greenhouse directly to cold temperatures outside. If planting in the summer or late spring, be sure to give new plants enough water for that first summer. Mulching with a 2-4" layer of organic mulch is an excellent way to retain water and keep down weeds.

Balled and burlapped trees can be planted almost any time, but usually do best if they are dug during the dormant season. If they are help past their dormant season, the root balls should be protected from drying and watered frequently.

Here is some good advice on Planting a Tree by Dr. Welch at TAMU.

Remember that it easier to plant a small tree and let it get established in the ground rather than planting a larger tree in the ground. There is a saying with some of our Master Gardeners that states: "When planting a tree, remember that smaller is better." I would go ahead and plant them this fall before it gets really cold, and be sure to put a good layer of mulch around the tree, not against the bark though, more of a tire-like form around the tree.

Like I already mentioned it would probably be a good idea for you to contact your county extension agent for horticulture information. They should have lots of good advice.