Ekka...
This summer, this might be as close to an article on this as you'll get.
If its what you had in mind, you could "blog it", cull this post, to the first line, and move it.
This is a casual commentary on what I think about when I select trees
The attached image is to show potential damage from buying trees with codominant leaders, from nurseries (see paragraphs below).
When a professional arborist or landscaper arrives at a plant nursery, they should already know what genus and species of tree to purchase, based on the needs of the customer and conditions of the site. But a substitute tree name may be needed too.
For my design projects, and some single-tree replacements, I list or consider a "back-up" or substitute tree, just in case option number 1 is not available. For example, I had some customers once, who wanted a 'Red Oblisk' beech tree. When I checked the website of the Nursery Association in our area, no Red Obelisk' beech were available - not until 6 months later.
You can't buy something that is not available.
Some trees never seem to be unavailable - just like nails and screws should not be unavailable at hardware stores. But its different for several other types of trees.
There are several ways that tree roots are contained in nurseries, including: balled and burlapped, pots and root bags.
The tree bags are similar in some ways to the rootballs wrapped with burlap and twine (balled and burlapped or "B & B"). But burlap is not designed to contain root expansion. If trees remain stored in chips or mulch for a while, balled and burlapped rootballs can grow roots into the backfill around them. On the other hand, root bags surrounding the rootballs are designed to restict root growth from extending beyond the material.
Personally, I prefer balled and burlap provided that the burlap is the kind that will decay and disintegrate after planting. That's because I can cut and remove the twine, but leave the burlap supporting the rootball. Usually, the rootball sustains minimal damage by not being rocked back and forth ripping a material loose.
Root bags - the ones I've encountered - restrict most root expansion beyond the material, but not all of it. Remember, the fabric can't restrict water, so there must be some small pores. Some little roots still seem to penetrate those pores and anchor the ball to the fabric.
I find that pulling or "fighting" the root bags loose from the root ball, seems to crack and damage rootballs much more than when I buy and install trees with balled and burlapped roots.
At least in our area, many balled and burlapped rootballs have soil similar to where the trees will be planted, since the trees were field grown in a "soil" rather than in a porous potting soil mix.
Potted trees seem to be among the easiest to handle, transport and plant, provided that they were not in the pot too long. If trees are in pots too long, roots start to "dead end" new growth at the pot's sidewall, then grow sideways, encircling the root ball. Or, the totally contained root development can "jam-pack" the pot with a mishapen root mass.
Either way, pots, bags, or burlap, its good to select trees that have not been stored in the nursery - or containers - for too long. This can vary: for some trees that would be like one year, for others, several years.
For ease, I enjoy the potted trees. Easy to move, lay sideways, and slide the rootball out of. But most of our potted trees are planted in potting mix that is like a fine or "coarsely-fine" compost. Like a fine organic mulch - which is very porous. That's good for the nursery because irrigation water can easily penetrate into the rootball. But it has drawbacks after planting at the tree's final home.
If a rootball has very porous soil, and the planting site has a heavier soil like clay or a loam, the planting hole and rootball can become like a quagmire from excess irrigation or heavy rain. Irrigation can be controlled, but rain can't. For this reason, balled and burlapped rootballs with "field" soil may be the best selection because excess rain will "run off" the rootball surface at almost the same rate at the site's soil.
When heavy rain falls on a site where "potted trees" were planted, excess rain flows off of the site in many cases, but keeps penetrating and filling up the pores of the rootball until its loaded with gallons of water. This can starve the tree of oxygen and cause other problems. One solution with potted trees, is to plant them an inch or two higher than the existing grade to deal with this potential difficulty.
As far as root containment, my conclusion is this:
I totally dislike rootbags. Potted trees are very easy to handle, move and store trees in. Balled and burlapped rootballs seem to be the optimum for good soil texture and irrigation after planting - whether the irrigation is supplied by people or by nature.
SUNBURN
Most tree professionals should be aware that trunks of planted trees need protection from sunburn in areas that get plenty of hot summer sun, until the trunks acclimate to the light, or the canopies spread with growth to shade the bark.
But how often do you see trees in nurseries with trunk protection for sunburn? Never?
For that reason, my practice is to never buy trees that are stored on the end of rows, where the tree trunk at the end is subjected to direct sunlight of the sun settiing in the afternoon. I'll almost always select trees from the interior of the rows.
Nurseries can move the trees around, but I believe that this practice is beneficial in most cases. This is also why its useful to stick with a couple of nurseries that you can keep and eye on and get a feel for the tree storage.
The two nurseries that I prefer, don't "juggle" the trees around too much. Usually, the trees that were in the row interiors, stay in the row interiors.
Again, that's why I avoid buying trees on ends of rows toward the sunset, or, any trees that I feel are getting to much sun on unprotected trunks.
Don't damage rootballs in the nursery: but I usually pull and wiggle each trunk a little bit to make sure that the roots are solidly anchored into the soil.
I select trees that are as free as possible from defects like weak "V" shape unions (co-dominant leaders), bark damage or dead tissue. The most common defect I encounter are the co-dominant leaders, which appear much more numerous in recent decades due to growers fertilizing to boost growth (equals more money faster).
Usually, in a row of about 100 tree, I find that only 25% to 30% would satisfy a trained arborist's "tastes" for good branch and stem structure. So I pass by the 75% and select from the 25%. Then, if I'm in "a pinch" for a few more trees, I'll pick the defected ones that have the most potential for corrective pruning.