Timber stand improvement (tsi) is something I get asked about quite a bit. Allot of landowners hear about it and wonder if they need it.

What is tsi?

Timber stand improvement is really just a heading under which a few different forest management practices fall.

Crop tree release is one such prescription and is a major practice under the general heading of “tsi”.

Crop tree release means, basically, just what it says.

The process is done by selecting certain trees that the forest manager decides to keep, called “crop trees”. These desired trees are then marked with a band of tree paint (Or a big dot on 4-sides.  The dots are usually reserved just on the really big trees, to save paint!).

Although the red “crop tree paint line” is fading after five years or so, one can still see the chosen crop tree, white oak, in the foreground.

These crop trees are your “keepers” – the one’s you’ll be managing for. Most of the time these are young trees, those that appear in good health, are vigorously growing, and have, at least, good potential for lumber and/or wildlife value.

What crop tree release calls for, then, is to “release” the canopies of the selected crop trees. This means that any and all trees that have a canopy that is within a few feet of the crop tree should be killed.  You heard me right — killed!  This scares the daylights out of some people.  And I know exactly how they feel.  It’s not easy winding your way around a white or red oak with your old Jonsered chainsaw roaring!  It’s especially not easy the first time you do a tsi job.  I mean it’s hard to think about killing good tree species!

But the truth is, one has to kill lots of trees to make room for the fewer good ones that the site can adequately support.  And support in terms of allowing the crop trees to grow to their full capability.  This 4-sided kill “releases” the crop tree to receive full sunlight to all the leaves on all four sides of the tree.  Thus, crop tree release is done to enhance sunlight to the canopies of the chosen trees.

This photo shows the canopy of the large crop tree in the back right and a now-dead tree in the foreground. The ultimate goal for the woodland manager with crop tree release tsi is a 3 to 4-sided “release” of the canopy around the desired crop tree.

It has been shown that this process can increase oak mast – acorn — production by 7-10-times the normal amount and, also, can increase the speed of growth by up to 2-times that of comparable trees that have not been released.   Crop Tree Management (PDF from ISU) (tons of great Info Here!)

The value of crop tree release TSI is HUGE to most Iowa forestland acres and there is very little, if any, debate in regard to the benefits of crop tree release tsi.

It is a win-win procedure!

A win for the landowner, in terms of forestland value. (And let’s not forget that cost-share dollars are readily available for various tsi procedures across the state — these can pay you up to 75% of the cost to do a procedure!)

And a win for the wildlife, in terms of fruit and mast production.

Not only is forestland mast production increased, but also the ground cover on the forest floor is enhanced via crop tree release.

However, make no mistake, the GOAL of crop tree release tsi, from a pure forestry perspective, is that of enhanced tree value, growth, and mast production, it is really not to thicken ground cover. That is a wildlife goal and is one that just sort of happens by default in many situations when crop tree release is implemented properly.

So the wildlife and forestry managers all get good results through crop tree release, in most cases (If the wildlife goal is not to thicken the understory, though,  crop tree release may not be a wise choice).

Another prescription that falls under the general “TSI” heading is understory release or site preparation for natural regeneration (SPNR)

This practice is specifically done just prior to, or right after, a major tree harvest. The goal here is to get rid of all undesirable small trees and shrubs that exist (example ironwood, young elms, plums, prickly ash, multi-flora rose, Japanese honeysuckle, etc., down to about 1- inch in diameter). These are not desired because they will shade out and kill the growth of any natural, desired, regeneration that exists on the forest floor (seedling oaks, hickory, walnut, etc.,).

To be sure, and as you may imagine, site preparation for natural regeneration is hard work that is very labor intensive. Again, this procedure is usually done only just before or after major canopy, tree-top, areas are opened up from a harvest or other factor (such as wind damage).

Most Iowa woodlands can greatly benefit from some sort of TSI – most commonly the crop tree release procedure.

In regards to the wildlife end of things – and whitetail deer in particular – both TSI prescriptions really provide a boon to deer.

The increase in sun-light coming down to the forest floor after a tsi procedure encourages a thicker habitat – this means more food for deer. It also means more security cover as well! The end result is that the forested acres become more attractive to whitetails at all times of the year – not just when the acorns are dropping. The result is an increase in deer carrying capacity of your property.

And, think about this, if your timber produces 7-10 times more acorns than does your neighbor’s woods, guess where most of the deer will be during hunting season?

Guess where most of the giant bucks will prefer to be?

And, not just because they get more food and cover there but because that is where most of the does are as well. You guessed it – on your land!

There is no doubt about it, deer live in the security cover that crop tree release can produce on the floor of the forest. Food and cover resources for deer are both enhanced by the crop tree release tsi procedure.

Crop tree release tsi often creates a thicker understory habitat which is highly favorable to deer and other wildlife!

Here you can see that it is OFTEN necessary to kill desired species to get higher quality crop trees. A couple of white oaks were killed here that were too closely spaced to the higher quality, and larger, white oak crop tree marked in the center.

It’s easy to see that crop tree release tsi normally results in a thicker understory habitat. The thicker understory habitat provides more food for deer and also better security and thermal cover as well. It also provides a favored nesting habitat for wild turkeys.

No doubt about it – TSI is not only a HUGE boon for your trees but it’s also a HUGE boon to your deer population!  Just to let you know, in case you may be wondering, timber stand improvement in general, and crop tree release tsi in particular, are the first things I do when I acquire a property.  It just makes your property better and more valuable!

Instead of asking why do tsi, the better question is why in the world not do timber stand improvement?

It’s certainly a win-win deal!

Many Iowa landowners are really into managing wildlife and wildlife resources on their properties these days. That’s really good! And many landowners really understand the value of doing wise forest management. That’s fantastic too! But, while all intentions are good, many Iowa landowners could probably use a little help with tree identification. Let’s face it, identifying trees is no easy task, especially in the wintertime when most of the leaves are on the ground. Let’s take a look at a few quick pointers that should help you in your wintertime Iowa woods in regard to tree identification:

1).  Walnut vs. Cottonwood

A quick slice into the outer bark of a black walnut shows that it has a dark inner layer.

The inner bark of the cottonwood is light colored — not dark, like the black walnut.

That’s right – these two species often get confused.  Sometimes really confused!  In fact, a forester friend of mine recently told me of a class he was teaching a while back on marking timber sales. The class members were let loose on a property and came back with over one-hundred thousand dollars worth of value on a bunch of big black walnut trees – some with veneer quality! They turned out to be all cottonwoods, with little to no value!

BIG mistake!

And these were forestry students with allot of education under their belts. This makes it pretty clear that you aren’t alone if you are getting the two species confused in your wintertime Iowa woodland. Check out the photo above for a quick way to tell the two apart with a little help of your pocket knife.  Note, too, that ash can also be easily confused with black walnut. The same knife technique works on the bark — the ash has a light colored inner bark while that of the walnut is dark. The same knife technique works on the bark — the ash has a light colored inner bark while that of the walnut is dark.

2).  Bitternut hickory:

The mustard-colored bud of the bitternut hickory is a telling feature.

This is a common understory tree in southern Iowa and if can get big, too.  It doesn’t just stay in the understory like hophornbeam (ironwood).  You’ll find bitternut hickory in the uplands mixed in with various oaks, You’ll find it in upland timber areas, commonly, mixed in with various oaks, hickory, and other species.  It’s common on moist slopes and in bottomland areas too. You can recognize it in the understory by the mustard-colored buds (picture above).

3).  American Elm

This white — American – elm show the buttress root characteristic that it ofen has.

The twigs of the elm are much thinner than that of an oak — and the buds of the elm are much smaller too.

This tree, believe it or not, can be confused with white oak.  And it’s best not to do that if you are doing timber stand improvement on your land! Elm has a thinner outer bark and smaller buds and twigs, than does white oak. American elm also, often, has somewhat of an exposed buttress root system. This can help separate it from white oak which too, which are less likely to have this trait.

4).  White vs Red oak

This photo shows the distinctive color difference of the black oak and white oak (white oak in the foreground).

There are two oak groups in Iowa. The red oak group and the white oak group. The white oak group has five species and the red oak group has six species in Iowa. The white oak group has – which oak, chinkapin oak, bur oak, post oak and swamp white oak. The red oak group has red oak, black oak, pin oak, northern pin, blackjack oak, shingle oak A quick guide to separate the two groups is – and you probably saw this one coming –  the color of the bark. The white oaks have whitish or lighter colored bark, as you may have also guessed. The red oak species have darker bark (usually).  (See pictures above). Black oaks – a member of the red oak group, are a typical species in southern Iowa that mix in with the red oaks.

Unfortunately,  Oak Wilt kills many really nice red and black oak trees in Iowa.  It’s a disease that can be contained somewhat through good management practices but it still can reak havac on your forestland acres.  Fortunately, the white oaks are pretty resistent to oak wilt and it doesn’t effect them very much normally.  Oak Wilt PDF (ISU)

The smooth flat-topped ridge of a red oak helps to distinguish it from a black oak, which has rougher bark. Also, red oaks tend to have less lower branching than do black oaks. (But the two species do hybridize and that confuses the issue!)

The bark of black oak tends to be rougher than that of true red oaks and black oaks tend to have more lower branches – on average – than do the white oaks.  True red oaks often have flat and fairly smooth ridges that are often lighter in color than the rest of the bark — ridges that may form sort of a loose diamond pattern on the tree trunk. Black oak and red oak can hybridize and take on characteristics of both. You tend to find more red oaks on north and east slopes and black oaks tend to occupy the dryer sites. White oak and black oaks often occur in roughly the same areas.

5). Shingle oak (red oak family)

The leaves of the shingle oak have no lobes — a telling feature!

Members of the red oak family tend to hold onto their leaves well into, and even throughout, winter until the buds start to swell in the spring.  That’s something good to remember. And for sure, shingle oak, black oak, and pin oak can look allot alike! But, you can tell shingle oak easily by the leaf. Shingle oaks have a single, elliptical, oval, shaped leaf with no “lobes”.  (picture above). No other Iowa oak has a leaf that looks anything like this.

6). Ironwood (Hophornbeam)

Hophornbeam — ironwood — gets this size and a bit bigger and often forms into dense stands in the understory. It can look like young white oak, but the leaves of the ironwood resemble those of an elm, not an oak, and the twigs and buds are slender and small on the ironwood.

Ironwood can fool you into thinking that you are looking at a young white oak. Ironwood is a common understory tree and often forms dense stands. It often carries leaves in the winter that resemble elm (not oak). Also, the bark is thinner than oak and so are the twigs and buds.

7).  Ash

Cutting into the bark of an ash tree will tell you if it’s really a walnut — since the two are easily confused. The ash tree has light inner cambium and the walnut is dark.

I remember as a kid riding my motocross bike up and down our gravel driveway with my friends. We had a lot of fun racing them around that’s for sure.  Though, I’m not quite sure how much the neighbors loved the noise! It’s a weird recollection to be sure, but every time I see the bark of a big old ash tree it reminds me of the tread I used to see on the back tire of my friends Suzuki RM 80 that always seemed to be in front of me! If you examine the bark of an ash, especially on a big older tree, you’ll also notice that it forms a diamond sort of arrangement across the surface, and the “peaks” sort of look like the tread of a dirt bike (sort of, you have to use your imagination a bit!) And as you can see from the picture above — the knife in your pocket will separate this tree from any possible confusion with this tree and the black walnut.

As for the twigs on ash trees, they have an opposite arrangement. This is a dead giveaway, in comparison to walnut and some others they may be confused with. (picture below) Also, the dreaded emerald ash borer is killing ash trees all over Iowa.  The young ash tree pictured below — bottom right — is a recent victom and is showing signs of the disease.  Unfortunately, there are several diseases and insects that kill trees of various species across the state.  You can find out more about all sort of tree diseases/pests/problems.

Branches arranged in “opposite” formation from each other is a key characteristic of ash — this easily distinguishes it from any walnut confusion!

The emeral ash borer has moved into Iowa and is killing the ash trees! This young tree is showing serious symptoms of the disease.

8).  Hackberry

The two hackberry trees — on the left — have deep rough ridges. (elm tree far right). The hackberry tree is pretty easy to identify once you’ve seen it a few times and it’s a good wildlife tree.

Hackberry tree often have deep cuts and ridges in the bark forming a very rough outer bark layer. A common tree with a good wildlife value – various animals eat the seeds. No other tree really looks that much like it, in Iowa, that I can think of.  But you still need to know what it looks like to identify it!

9).  The dreaded honey locust!

The thorns on the honey locust can run up to 8- inches or so and are very sharp. One interesting thing about these trees is that bout 10% of them, in Iowa, are thornless. The trees that do have thorns can easily go right through your boot or tractor tire, so watch out!   But, honey locusts are great trees to leave for deer because whitetails love eating the seed pods in winter.  Deer often seem to favor pods off certain trees vs. other for some reason.  This one is easy to I.D!  (Black locust trees may seem similar but tend to form straighter trunks and have smaller spines, than that of honey locust trees.  Black locusts were often planted in the “pioneer” days for fence posts and firewood, and you can see groups of black locust tree, often, around homesteadsteds.

Most people can’t mistake this tree for anything else — the honey locust. It has scary sharp spines that’ll go right through a tractor tire or boot. But, it does produce seed pods that deer love to eat in the wintertime!

10).  Shagbark Hickory

This one is pretty easy for most folks to I.D., because of the long scaly bark.  A common upland tree in Iowa, occurs in groups of mixed with oaks.  Can dominate dryer sites.

The scally bark of this shagbark hickory is hard to confuse with anything really. These trees are common in the upland woods and can dominant dry sites.

For more help identifying tree in Iowa be sure to check out ISU’s interactive tree guide!

We also have lots of useful resources on our resources page (makes sense, right?)

You might want to get Iowa Trees and Plants Iowa Trees and Plants (PDF)