We know that most growth of a tree trunk occurs on a horizontal plane as the trunk increases in girth. However, it seems some growth also occurs vertically as well. We've all noticed on trees which have light-colored bark and which grow very stout, such as on beeches, how bark wounds and other marks expand in time in both the vertical and in the horizontal dimension.

My previous inquiry at this forum (about "Nailing Signs on Trees") showed that nailing any object to a living tree is a BAD idea, as the nails, and maybe even also the objects which they attach, would be engulfed by the trees' growth.

For this reason I've tentatively decided that our hundreds of real-property conservation-easement boundary marker signs will be mounted on trees, but not by use of nails. Instead we'll use long, heavy-duty, hex-headed galvanized steel screws which can be "backed out" periodically as the trees grow. We'll crank them out periodically by using socket wrenches with long "breaker bar" handles.

We were planning to mount our rectangular signs with their long axes oriented vertically. One screw would be attached at the top of the sign and another at the bottom. I expected the only significant growth of the tree trunks would occur on the horizontal plane, as the trees increased in girth. However, now I wonder if the two screws will gradually spread apart as some growth also occurs on a vertical plane.

Am I correct?

Would this suggest any "dual-screw" attachment to a living tree is "doomed," and that use of a single screw would be better? In that case, how would we maintain the desired vertical orientation of our signs, and how would we keep them from "twirling" on a single attachment?


Jeff Hook
New Jersey, USA

Reply to post by Jeff Hook, on December 30, 2001 at 20:58:01:

Jeff,

Trees do not expand in the vert. dimension as you have expressed concern. Trees grow from the tips upward and outward, and radially from cells generated annually by the cambium layer under the bark. The two screw system will not spread apart, however I am concerned about backing out the hardware. You will find that if you back out the hardware after say, 5 years, that the 5-years of growth that has developed since the hardware was installed will be damaged and the tree will have to go through a chemical and physical defence process called compartmentalization. Eventually the defect that was caused by the initial installation will be increased in size. I am more in favor of replacing the sign at some future date in a position that is not aligned with the previous installation, and using hardware that can remain in the tree.

Wayne

Reply to post by A Wayne Cahilly, on December 30, 2001 at 20:58:01:



EXCELLENT, Wayne! Thank you very much!

You might believe the enormous amount of work which was required to reach this point of "satori"! First I began with my own tree-maintenance books, which I hadn't absorbed in their entirety, and which may have discussed this topic, but which didn't indicate any mention of it in their indices. Then, as I discussed in the other thread, I went on-line.

I was gradually educated that metal fasteners hammered or screwed into trees will remain there and will be engulfed. For that reason it seemed appropriate to attempt to use steel fasteners which could be "backed out" as needed. Just as I was becoming attached to this idea for other than purely objective reasons you seem to have shown me "the true light"!

If I understand you correctly, you're saying:

1. Yes use metallic fasteners in a vertical line, on the top and on the bottom of a rectangular plaque or sign, but

2. No, don't plan on attempting to "back out" those fasteners, as that really WOULD injure the trees.

3. Therefore, if the fasteners will never be "backed out" and the trees will engulf them over time, use aluminum, as it will not endanger any future "saw-wielders."

This "cures" me of my error before my commitment to the "back out" idea reached the terminal stage. Not only that, but it greatly reduces the labor, which a more practical person than I would have seen was surely too much to be realistic. (All the biennial "inspection and back-out tours" would surely have been too much to have occurred as anticipated!) Periodic wholesale REPLACEMENT makes much more sense than some unrealistic plan to ADJUST all the attachments over time.

You've answered definitively in this thread my last "re-submission" of my inquiry about tree injury, so I'll note that thread now.

Eureka at last! Thanks very much!

Jeff Hook

Reply to post by Jeff Hook, on December 31, 2001 at 10:29:41:

Jeff

Be cautious when using aluminium fixings on trees, they are chainsaw friendly but in the UK we find that squirrels have a taste for aluminium. I have used alloy roofing nails of approx 3mm dia. to attach tree tags and had to re-tag the trees the following year. the squirrels usually nibble the heads off but occaisionally the shanks also . Perhaps a greater diameter would be more of a challenge?

I'm not wholly convinced that backing the screws off would be a major problem but agree with Wayne that damage could occur through delamination of tissues.

We have been experimenting with galvanised nails to attach tree tags. We place the 75mm nail through a predrilled hole in the steel tag and then through a 50mm long stainless steel compression springfollowed by a stainless streel washer; this should allow the tree to grow radially by 50mm before adjusting. We have tried the same system without the spring and washer and the tags and nails wear at the point of contact. Another method, which I haven't used is to pre drill the tag and drive the nail down at 45 degrees, allowing growth to push the tag up the nail. I guess that signs could be attached using any of the above by just scaling up the dimensions. Perhaps 2 @ 10x100mm stainless pins driven at 45 degrees would hold the sign agains the tree.

Mike

Reply to post by mike, on December 31, 2001 at 16:49:34:

Interesting about the squirrels. There was a post some time back about them chewing on the aluminum tree tags themselves (the little, round forestry type tags).

If you shop carefully you can find stainless steel common nails. Not too chainsaw friendly, but no corrosion or toxicity problems.

Reply to post by mike, on December 31, 2001 at 16:49:34:



I'm very appreciative of the excellent and authoritative comments which have been offered from the UK and from the US. However, I'm absolutely amazed at how intractable this seemingly-simple problem is proving to be! WOW! At each step thereÂs some Âcontraindication.Â

Your comments are clearly informed by solid experience, so it looks like exposed aluminum may be "out" and, unexpectedly, I might be swinging back to steel fasteners which are "backed out" periodically, if I hadn't been shown the many defects of that method.

As much as I value Wayne's advice, a closer study of his description of the NYBG method shows that it seems his softwood plaques AREN'T held at any distance from the trunks of the trees when they're first installed. (As Scott put it, they donÂt Âstand off.Â) Instead, they're nailed directly against the tree trunks, and the heads of the nails are even counter-sunk in the "outside" surface of the plaques. As the plaques are in direct contact with the trunks when they're first installed, there's no extra fastener length to hold them out from the trees, and there's no "gap" for advancing tree growth to fill before the signs are pushed off the aluminum screws.

(Wayne's explanation of his "softwood plaque" method is in message # 1717 in the other thread. I wish I never began a second thread about this same topic. Mea culpa.)

As JPS suggested in message # 1711 (again in the other thread), the plaques could be made of weather-resistant wood, such as red cedar, rather than of weather-susceptible pine.

However, we have a very large number of signs to install. IÂd like to assure these signsÂd be very durable, that theyÂd remain attached securely for the longest-possible time, and that theyÂd require the least amount of maintenance. IÂm beginning to think all of this may be a vain hope, and I may soon conclude the only practical approach to take is to obtain weather-resistant, but hardly Âpermanent, plastic signs, which wonÂt be too expensive. We could then just hammer them in, directly against the tree trunks, possibly with rather short, broad-headed aluminum nails (siding nails come to mind), and be done with it.

This is despite the caution which has been expressed about aluminumÂs malleability, about its Âpalatability to squirrels (which I guess are really just honing their incisors rather than savoring the taste of aluminum), and about the development of cracks in the wood if we donÂt pre-drill for the nails. In cases of very rough, fissured bark we might wish to apply our stiff, heavy-gauge rigid plastic signs over some weather-resistant plaque.

WeÂd be using the same method for installing our signs as is used for nailing, tacking, or stapling the impermanent, heavy paper ÂNo Trespassing and ÂNo Hunting signs with which weÂre all so familiar, except our signs would simply be attached by use of aluminum rather than steel fasteners. When the signs were in danger of being torn or pushed off their nails, we could just tear them off ourselves, leaving the original nails Âin situ and installing new signs at the same height, but one sign-width to the side.

It looks like this would be the cheapest, simplest, least-injurious alternative. It just doesnÂt look like any other method will really Âdo the trick. It was a valiant effort, but I fear itÂs just not Âpanning out.Â

IÂm ready to Âthrow in the towel on this.

Jeff Hook

Reply to post by JeffHook, on January 02, 2002 at 12:44:21:

Don't be too quick to capitulate to such a simple conundrum, Jeff. Let's summarize-

You need to hang a bigbuncha signs, and trees seem the logical choice for sign posts. The problem is how to hang the signs so that:
1) You cause minimal damage to trees.
2) The signs remain in place for a reasonable time.
3) Minimal cost and labor is needed to install the signs.
4) Minimal cost is involved to maintain the signage.

Now let's look at the responses and the impact of each item.

1) Minimal damage to trees- It seems we're looking at some natural trees in a wooded tract, not the front lawn of the Governor's Mansion. Another couple of small holes will probably not make a significant difference. Pre-drilled, screws, or nails will not matter all that much. The hardware will not move relative to the ground. Any hardware installed should be left behind when the signs are repositioned or removed, and not "adjusted" once installed.

2) Durability of signs- The installation hardware should last as long as the signs. How long is that? Can you expect 5 years before painted signs are too weathered to read? Plastic signs also fade. Few trees in a wooded area grow as much as 1/2 inch per year, so 2" gives you at least 4 years (that's 2" clear room on the shank). You will probably get more like 6 to 8 years on hardwoods in New Jersey (or 30 years in the Pine Barrens).

Steel, aluminum, brass, stainless- all will do the job, and probably all will last at least as long as the signs, despite squirrels seeking aluminum salts from the corrosion.

3) Minimal installation cost- Keep it simple. Nails are easiest, can be done with simple tools (rocks), and can be installed by one person. To give you durability, you need to leave a long shank exposed, but without much movement of the sign. Get a bunch of old bicycle tires, cut into strips, and fold them behind the sign. The nails drive right through, the rubber holds the signs firm but compresses as the tree grows. Hardly seen behind the sign.

In the graphic above, the system is simple. A sign, two nails, two washers, two springs. It shows the spring outside the sign, but it can go between sign and tree. If you use a rubber spacer, put it behind the sign to hide it.

4) Minimal maintenance cost- Again, keep it simple. When the sign must be replaced or repositioned, use bolt cutters or a heavy-duty nail cutter to clip off the nail heads (easier with aluminum). A few new nails, new sign if needed, and you're right back in business. You can leave the old shafts in place if they are firmly set, and there is little chance the trees will make it to a sawmill.

Here again, we're not talking specimen landscape trees. The amount of damage done by pulling the nails will not be all that great. Sure, you'll have a few defects in the wood. Compared to ripped branch stubs from storm damage or squirrels chewing gaping holes around old wounds, this is minor. As arborists, we tend to lose sight of the practical in favor of the absolute, since trees are our passion.

What you are planning, Jeff, and the care you are obviously putting into looking after the trees, is not all that harmful. I see trees with bear rips, cat markings, wire fences embedded, shotgun blasts, tractor scars, and a whole host of natural calamities that survive and even thrive. Your biggest concern doesn't have to be the trees.

Reply to post by Russ Carlson, on January 02, 2002 at 19:21:41:

Hi Russ, you wrote ". It shows the spring outside the sign, but it can go between sign and tree." If the spring was between the sign and the tree I suspect the tree would simply consume it, unless you had a very large washer on the trunk side of the spring. It would, however, serve very nicely to protect the trunk from impacts of anything falling against the sign!!

Happy New Year, James.

Reply to post by Russ Carlson, on January 02, 2002 at 19:21:41:



Russ:

I'm not able to reply in detail right now, but let me just say, for the moment: WOW!

It's obvious you're an authority, and that you know very well "whereof you speak." It's obvious you're an intellect, because youÂve not only perfectly summarized every element of this "conundrum" (as you so appropriately characterize it) but you've simplified and clarified it beautifully, with excellent judgment and insight. Needless to say, that's very helpful. Your prose is eloquent, and your illustration is superb!

The "properties" of your name indicate an E-mail address which suggests you're moderating this forum, and if that's the case I can only say it seems to be in very capable hands. Look, I know this will seem grossly excessive to everyone else who reads this (you're entitled to enjoy it secretly, as you've certainly earned such high praise!), but you do appear to be, as Matthew Arnold might have put it, a "Scholar Arborist," or as Plato might have put it, a "Philosopher Arborist." IÂve seen enough evidence during this year-end inquiry of mine to wonder if trees just naturally attract thinking people.

I've received many, many helpful replies from all over the English-speaking world, and I'm minimizing neither their excellence nor my gratitude. One other reply, in another forum, stood out as exceptional, for visual impact and for ancillary qualities, not only for its illuminating comments about trees, but this one is wholly Âon topic, and, for sheer practical value, it must be ranked as the best by far. Your superb use of this medium has shown us what it can do for communication, for the dissemination of information, and for EDUCATION. Imagine what the future holds for this type of electronic communication. Again I say WOW!

IÂll reply later in detailed response to your recommendations (in part because itÂd be absurd to juxtapose my inane comments to yours in this message!).

ÂWhew!Â

(Oh, by the wayÂTHANKS!)

Jeff Hook

Reply to post by Scott, on January 02, 2002 at 12:44:21:



See Russ's "mind-boggling" reply in this thread, which really "bears away the palm." I'd thought the squirrels were merely exploiting an opportunity to gnaw on metal which was hard enough to hone their incisors but not too hard to break them. Russ has suggested (and I think knowledgeably) that they're actually attracted to the salts which accumulate from the corrosion of the "aluminium." The commentator from the UK (his E-mail suggested he might be a forester from the "Cheshire Woodlands") didn't offer any hypotheses about why they might be gnawing on the nails.

Both you and Russ seem much less concerned about introducing "chainsaw resisting" metallic foreign objects into the heartwood of trees than I am. I've copied this entire thread into my word processing file here (as you can imagine, I've got an enormous directory on this topic now, and it's still growing). I was studying your earliest comments last night, after I'd begun to think I'd "made much too big a deal" out of all of this, and after I'd posted my "notice of capitulation" here. I thought, "Yeah, he was 'right on the money' at the outset. This really isn't 'that big a deal'." However, I'm still loath to use steel, as I just can't see us introducing thousands of potential hazards into thousands of our trees, even if "Joe Sixpack" will be cutting up this timber in the future with a "shoulder-mounted laser," rather than with a chainsaw. When I reply in some detail to Russ's superb message it'll be on that score, as I hope he's not overlooking the "squirrel vulnerability" of aluminum.

His comments have me gravitating back towards the use of "oversized" aluminum nails which we can use to really "stand the signs off" the trees by following his excellent advice about mounting techniques AND which we can in good conscience allow the trees to engulf. TheyÂd be Âlunkers, so maybe weÂd pre-drill them a bit to preclude wood splitting, and I appreciate your sage advice about ÂaluminiumÂs intolerance of pounding, but at least, as I say, the trees could incorporate them without creating any hazard.

Jeff Hook

Reply to post by mike, on December 31, 2001 at 16:49:34:

Interesting about the squirrels!! We average 20 squirrels per Ha2 here and use both aluminum screws and aluminum accession tags and have never had a problem. Must be a european taste *G*

Wayne

Reply to post by JeffHook, on January 02, 2002 at 12:44:21:

Jeff,

They do stand out about 1.5 to 2 inches. The screw heads are countersunk in the wood backing so that the sign can be double-stick taped over the screw heads achieving two things: 1. the heads do not show and 2. the sign is held tightly at the head-end of the screws so that it cant move.

Reply to post by James Causton, on January 03, 2002 at 15:59:53:

James,

Good point, we do the spring thing for our aluminum accession lables and we put the spring to the outside. In this way the tag itself acts as the washer, and when we did it the other way around the tree grew around the springs. Adding an additional washer against the trunk adds cost, time and one more thing to forget in the shop.

Reply to post by Wayne Cahilly, on January 02, 2002 at 19:21:41:



Yes... "Mea culpa." I saw that last night, as I reviewed my file to which I'd copied this thread and I thought "I really 'studied' his message well, didn't I?" Your explanation of your method made this "stand off" factor very clear.

JH

Reply to post by Wayne Cahilly, on January 02, 2002 at 12:44:21:



Could "aluMINium" be "lookin' good" here in the US after all?!

JH

Reply to post by Wayne Cahilly, on January 03, 2002 at 22:15:58:

We had a project many years ago and we found a custom spring shop. They made up a batch of conical springs... dia at one end say 0.5" and at the other small enough to fit under the head of a 16d common nail... which we installed outside the sign. (Sorry Wayne, I cling stubbornly to non-metric units).

The other thing we learned is that both plastic and aluminum get hammered by the UV light. The plastic tends to go yellow and gets brittle. The black anodized aluminum with mill finish where the plaques were engraved bleached out within a year in direct sun. ( and they looked sooo cool out of the box).

SC

Reply to post by James Causton, on January 03, 2002 at 15:59:53:

So what? If the spring is "consumed" by the tree, it still performs its function of keeping the sign held against the nail head, and keeping it from excessive movement against the shaft. Only a problem if you intend to remove all traces of the hardware sometime.

Reply to post by Jeff Hook, on December 30, 2001 at 20:58:01:



I began my inquiry almost two weeks ago, and thanks again to everyone who contributed. This forum has provided excellent assistance. IÂve pretty much Âhad it with this topic, and I therefore assume all of you have as well. I can guarantee these are my final questions (if anyoneÂs still inclined to answer!)

1. Our squirrels here in southern Hunterdon County, NJ are less than 70 miles from WayneÂs and I therefore assume theyÂre all members of the same Âtribe. If WayneÂs smart NY squirrels havenÂt been chewing aluminum, IÂd assume our Âcountry bumpkin squirrels wonÂt bother any exposed aluminum here. However, IÂm very reluctant to go to the trouble and to the expense of installing well over a thousand aluminum nails, which would all be exposed to the squirrels as Russ suggested, if theyÂd only be seen by the squirrels as Âcandy bars and as Âwhetstones.Â

Does everyone agree that the squirrelsÂd be unlikely to attack the nails, but even if they did theyÂd not cause serious damage? I must look into the types of aluminum nails which are available, but I guess we might be able to find some which are almost 5 mm-3/16Âin diameter, and I wonder if such a Âspike would be able to withstand the worst squirrel gnawing.

2. I assume the effect on aluminum which Scott attributed to UV radiation doesnÂt compromise the nails Âstructural integrity and is only an appearance problem.

3. Even though nails seem to be the preferred fasteners for a variety of reasons, as Russ pointed out so well, and although the characteristics of screws are moot, IÂm still curious about a comment which came from someone in the UK whoÂs very familiar with orthopedic screws. I wonder if any of you can clarify this as the official Âfinal point of this inquiry: He advised screws would only be difficult to extract if they incorporated an unthreaded portion between their heads and their threads. He expected the new wood to grow so tightly around that narrower shank that the threads behind it would encounter difficulty in attempting to Âbite through the new wood. He said fully-threaded screws might be easier to remove, Âpace WayneÂs remarks about aggravation of the trees compartmentalization process, etc., etc.

Thanks very much to everyone, with added thanks again to Russ for his spectacular contribution. Not only were his comments very helpful overall, as I mentioned previously, but he was the only one to quantify the annual growth rate of trees and the life-expectancy of signs.

Jeff Hook