Tree Growth Regulators

When we returned from a recent business trip, we found a note hanging on our doorknob informing us that something called a “tree growth regulator (TGR)” was going to be applied to the beautiful live oaks in our front yard. The note, left by something called Edko Vegetation Managers, explained:

A tree growth regulator (TGR) will be applied to selected trees along the overhead power line rights-of-way. TGR’s (sic) gently slow tree growth, while also producing a healthier and greener tree. Edko, LLC has been contracted to apply tree growth regulator to selected trees routinely, or soon to be routinely, trimmed away from the power line facilities. Please use the number below if you wish further explanation of the work.

Needless to say, we did in fact wish further explanation of the work. To be specific, we wished to receive further explanation of the work. But then, we, being graduates of elementary school, also tend not to use apostrophes to denote plurality. So we called the number, reaching an automated message that informed us the TGR in question would be a chemical called Cambistat and that we should leave a message. So we did.

The kind folks at Edko, LLC, called back and it turns out that Cambistat is one of several TGRs on the market. You can read the label here (caution: that link is a PDF). The active ingredient is Paclobutrazol (22.3%), with a mysterious group of “Other Ingredients” comprising the remaining 77.7%. This reticent labeling strategy alarmed me, and it turns out I’m not alone – residents of Elkhart, Indiana, were very concerned this past July about plans to put this stuff on their trees. But overall, we were surprised at a general lack of suspicion of TGRs out on the Internets. Which is kind of weird, because basically everything in the world no matter how innocuous (think Strawberry Shortcake or penguins) has a whole host of online detractors willing to accuse it of causing genocide — or at least cancer.

The idea of TGRs seems to be that they change a tree’s hormonal balance in a way that they direct less energy to branch production and more energy to other parts of being a tree – like leaf production, root growth and bark strength. When we called the people at Edko they were quite concerned that we learn about the positive side effects of TGRs. They also explained how the application will work. Essentially, we can expect that at some point an Edko employee will arrive with a solution mixing one part Cambistat to 11 parts water. That solution will be injected into our soil about a foot from the trees’ base and about 4 inches below the grass. It will be absorbed by the tree, slowing its limb growth. We were told to expect golf-ball sized holes where the probes went into the ground, and were told the treatment should last from 3-5 years.

How did we get on the list? Evidently the power company is looking at trees within 15 feet of power lines. Ours are right up next to them, and we’ve been waiting for the day someone comes to hack them back. Two years later, we’re evidently headed for a chemical solution. We are not totally sold on Cambistat or TGRs, especially when old-fashioned (admittedly more expensive) tree trimming would seem to do the job just fine. But since it doesn’t look like anyone out there is providing much credible evidence for adverse human health effects (other than drinking the stuff, or marinating rats in it), we guess, as long as it stays out of the drinking water, we’re okay with it (and we’re not wading through seemingly-ominous Brazilian agricultural science journal articles on the topic written in Portuguese). Plus, it’s not like we have a choice in the matter.

Or do we? Some people may have gotten this notice and been concerned about the legal implications of these chemical applying folks walking all over their property injecting some kind of solution into the soil. Are they allowed to do this?

Well, put away your rock salt, shotgun and neon “no trespassing” signs, because you’ve almost certainly given the power company legal permission to enter your land to maintain their lines. In legal terms, we’d say that you’ve granted them an “easement” as a condition of you being able to use their electricity to power your precious television (and air conditioning, etc.).

Now, they shouldn’t be able to kill your trees, stop on your prized tulips, or give you cancer with their tree-growth-inhibiting chemicals, but since Cambistat has only been on the market since 2003, you’re not likely to know about the latter eventuality (should it happen) for several years down the road.

It’s almost enough to make you nostalgic for the folks in the bucket trucks with the chainsaws.

Kate and Stephen are Midtown residents with a cat, a garden, an old house and a sense of adventure. They write about life in Midtown here and about life in Montgomery at their blog Lost in Montgomery.

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There Are 16 Brilliant Comments

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  1. Gabbie says:

    Sigh. Thanks for the heads up. We have a big willow oak that is about 15 feet (I think) from the street. I wonder if we’ll being seeing these guys too. Grrrrr…..

  2. Jay Croft says:

    I’ve been begging the power company for YEARS to trim the tree in front of our house. It is directly underneath the power lines, the cable lines and the telephone lines and whatever. The branches are tangled in the lines.

    Nope. I guess they prefer that the tree be felled by wind or lightning and the power, cable and telephone go out first. Then they’ll come out and fix the problem, at far greater expense.

    Oy veh.

  3. Jay Croft says:

    This “tree growth regulator” sounds something like the pill I give my dog to prevent fleas. I do not see how the H a once-a-month pill can be effective against an external parasite–but apparently it works.

  4. admin says:

    We received this comment from Russell Stringer, an Urban Forester in the City of Montgomery’s Planning Controls Division:

    “Alabama Power Company requested and received permission from me to use the TGR on public rights-of-way. They are also targeting trees on private property to use this chemical on. What you may not know is that they do not have the RIGHT to do this, as is implied on the door hangers.

    I received a bunch of calls concerning this and contacted the local company representatives. I was told anyone could call the number on the door hanger and refuse service. Apparently if you DON’T call, they will “assume” that you are granting permission. It seems to me they are banking on homeowners assuming that the utility providers have the legal right to do whatever they want. Personally, I don’t particularly care for this way of doing business.

    That being said, to the best of my knowledge TGR has no adverse effect on the health of trees. I have been in contact with Mobile’s urban forester, who has permitted work like this for several years and seen no ill effects. I will continue to permit the use of this chemical on the street rights of way in Montgomery.

    I do wish you would let your readership know that if they don’t want chemicals sprayed on their private property, they need to call the number on the flier and refuse service. Anyone who would like to contact me about it can call 241-2740. If you get the answering machine, leave a message. I return all my calls.”

  5. Katie says:

    I wish Russell’s comment could be displayed more prominently. I almost missed it, and it is important!

  6. Jim says:

    Cambistat is a valuable arboricultural tool. It is frequently used in residential and commercial situations for the plant health benefits associated with applications. It is also used in utility right-of-ways to reduce the growth of the trees near the powerlines.

    I would like to comment on a statement above “Cambistat has only been on the market since 2003, you’re not likely to know about the latter eventuality (should it happen) for several years down the road.” It is true that Cambistat has only been on the market since 2003, but soil applied TGRs have been on the market since 1992 and the active ingredients in TGRs have been researched since the 1950s. This product has been thouroughly researched and is EPA approved and registered in every state.

  7. Stephen says:

    Thanks for commenting Jim. Something can be a “valuable tool” and still have bad effects. DDT was also a “valuable tool.” It just happened to also kill people. It was also approved by the EPA … until it wasn’t. So the fact that a chemical has passed the industry-controlled standards of the regulatory rubber stamp process is far from a reassuring statement, no matter how many states the product is registered in. We’ll continue to prefer a different “aboricultural tool”: the saw. No threats to the water supply there.

    • Jim says:

      Stephen, of course something can be a “valuable tool” and still have bad effects. It is hard to compare an older chemical like DDT with some of the current products on the market. When DDT was broadcast sprayed across the environment it did have some negative effects. Cambistat is applied to the soil just below the surface not sprayed on everything in sight. I would make the argument that a chain saw also has the potential to threaten the water supply. A chain saw runs on gas and oil which are chemicals that are much more dangerous to the environment than Cambistat. I am sure nobody has ever spilled gas while pruning your trees. The key is that as long as the chemicals are being used in the correct manner the risk is minimal. We often don’t think about everyday products because we are familiar with them. Cambistat is unfamiliar to people so they think it is dangerous. Everybody handles gasoline on a regular basis and they aren’t concerned. Chemicals are an essential part of our lives and we need them for many things we do. The key is to understand them and handle them properly by following labels and utilizing them the way they are intended.

  8. Stephen says:

    Jim, welcome back to the conversation. I hope you didn’t spend the 3 months since your last comment thinking up this latest contribution. It’s actually not all that hard to compare an older chemical like DDT to current products on the market. There are scientific standards designed to do just that. When DDT was banned, it’s not like we burned all knowledge surrounding carcinogens and erased any sort of baseline by which to measure effects of current chemicals. So actually, it IS possible to compare chemicals across time.

    Further, you make a valid and irrelevant point about how gasoline is also a toxic chemical. Not only does the existence of one bad product fail to justify another, but gasoline, unless spilled, doesn’t go into the ground. Cambistat does, and gets into the water supply. That’s how it gets into the roots of the tree. So it’s not a zero-sum tradeoff that decreased Cambistat means people will soon be sloshing gasoline all over our yards. In fact, you can prune many trees with a hand saw.

    And let me close with an encouragement for you to actually look at some of the studies that are out there about Cambistat. I won’t provide all the links here in the comments section, but the insufficient research that exists is reasonably available. Maybe you are willing to shrug off “minor skeletal defects” and “fetotoxicity” because, well, all chemicals have some bad effects but humans are super awesome and we’ll handle it. For me, I look at costs as well as benefits and make a call. And unless you’re getting paid by the company that makes it, maybe you should do the same.

  9. Alex says:

    “Admin” – thank you for the information. I had no idea I could call and refuse the service. The message on the door hanger was pretty straightforward – you have no choice! Unfortunately it’s too late now. “… no adverse effect on the health of trees…” Sure… Alabama Power applied growth regulators to our beautiful pear and maple trees last year (by the way, it was totally uncalled for – there was no way those trees would come in contact with power lines!!!). NOW THEY ALL ARE DYING!!!!! 50% of the foliage is missing and the leaves that are still there are small and deformed. I feel like crying every time I look out the window. Does anybody know if there is a way to save them? Please help!!!!

    • admin says:

      You should call Russell Stringer over at the city, Alex. Get some info from him and see what kind of advice or help he can suggest. That is terrible news!

  10. Jim says:


    Yes you can compare chemicals from different generations, but the point was that we have learned a lot over the years on how they are applied, what risks they pose, and the effects they have on people and the environment. Using DDT as an example; the product used to be sprayed all over everything. There are pictures of kids walking through the chemical like it was a sprinkler. During Vietnam our soldiers walked around in the jungle after defoliators had been sprayed all over from helicopters. It is not surprising that there were some negative effects from these incidents. If you look at Cambistat being applied to an average 20″ oak tree you are talking about 250 ml of Cambistat being mixed with 2,750 ml of water and applying it into the soil near the base of the tree. Cambistat has a low soil mobility and it will adhere to the soil where it is taken up by the tree through the roots.

    The point with gasoline or any other chemical is that if they are used properly by the label and at the correct dose they pose minimal risk. We handle gasoline everyday and it is much more toxic than Cambistat. We understand how to utilize the product. Yes gas only goes in the ground if it is spilled, but it goes into the air all the time and so do the by products from burining gasoline. Also the logistics of using a hand saw all the time is unrealistic. If you have ever worked on a tree crew you know that production would be nonexistent and the cost of pruning trees would go through the roof. Which also means the cost of our electricity would go through the roof.

    As far as this comment from above, – “the insufficient research that exists is reasonably available. Maybe you are willing to shrug off “minor skeletal defects” and “fetotoxicity”.” I would love to see your data to support this! I have looked at the studies surrounding this product.

    • Cindy says:

      Jim, I read your comments on your thoughts about the Cambistat and the chemicals used to make it. I became interested in this subject when I found out it would be used on our local tree’s. While I am sure you have good intentions and are trying to “educate” the population… I have an “education” on Chemicals… ground water/soil contaminates and “safe” levels of chemicals. Also what the “EPA” deems safe and the effects if they are wrong. It seems like it is still early to say if Cambistat is “good” or “bad” but I warn anyone who thinks using chemicals in any way that you must consider the long term effects. Water and ground is contaminated… you may as well say forever… because it won’t be gone in your lifetime. Chemicals have longterm effects (and I have never known them to be good.) on people & wildlife. Once its in the ground water and soil… Its there. It doesn’t matter if its dropped from planes… or dropped ever so carefully on roots of the tree’s. It will still then contaminate tree’s, plants, wildlife, ground soil and the water supply.
      I am unsure if you have any experience with Chemical contamination… But I have… First hand… and over 3 generations. In upstate Ny. a company was given permission to dump chemicals in our town… they chose several locations and the long term effects on many???? Not great. I don’t know how many chemicals they dumped into the soil… But 81 chemicals were found and many in toxic levels. Chemicals were dumped in 2 locations within my childhood home. One location 2 blocks away… and another maybe 1000 ft. from my back yard. My mother developed cancer quickly and was gone by the time I was 4. I am now 43 and have had a long medical history of cysts and tumors. Of my 3 children 2 were born Autistic and had health problems. Our environment doesn’t “Need” more chemicals. It needs less… If the problem is tall trees? The answer? Cut them down. If you still want a tree there… plant another… I LOVE the environment and tree’s. DO I want tree’s cut? No. But I do want my childrens children to be safe.

  11. Billy Jones says:

    I thought your readers might be interested in a recent online conversation I had concerning Cambristat and the reluctance of its users to answer the simplest of questions: Please skip the local politics at the beginning.

  12. April Doss says:

    And here they are in WV same BS. But here is the weird thing I signed release papers for local tree trimming company to trim my walnut tree. When Edko showed up I called Asplundh tree service they were shocked Edko was going behind them injecting TGR into trees they trimmed. I said no to TRG, it reduces fruit, nut growth by 70%. April Doss, Belle,WV

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