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Plant Growth Regulators: Safe?

Plant Growth RegulatorIt may be too late in this season for us to start our own vegetables and flowers rather than buy nursery stock. But there’s a good reason we should at least be aware that the starts we purchase at the nursery or big-box home supply store may have been treated with plant growth regulators (PGRs). It’s also a good reason, short of growing our own plants, to make sure the nursery stock we buy is from a reliable organic dealer.

The term PGR has come to include many things, not all of them potentially harmful. But technically, a PGR is a spray or chemical used to treat seed or growing plants that, through cellular mutation, makes the plant in some way more desirable, often more to the seller than the buyer.

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PGRs are used for a host of reasons and function in a number of ways. They are commonly categorized and regulated as pesticides but mostly deal with growth, flowering and fruiting issues. Some, especially those used to encourage rooting, are organic compounds. But most of those used in commercial agriculture — and that includes the sale of nursery stock — are synthetically derived.

Here’s an interesting paper on the growth regulator Sumagic. Notice that there are strict restrictions on how much and when this PGR can be used. Scroll down to “Post Transplant (sic) Concerns” to find that one concern is residual Sumagic in the fruits. These are the kinds of things that make us suspicious.

Why use them at all? “PGRs like Sumagic are gibberellin biosynthesis inhibitors which suppress plant height by inhibiting internode elongation,” says the report. In other words, they keep plants — in this case tomatoes, peppers, eggplants, tomatillos — from becoming too leggy.

It doesn’t take much to figure out why commercial nursery growers might want to discourage large growth. Here’s Joseph Tychonievich discussing PGRs from his wonderful new book Plant Breeding For the Home Gardener (more on this great resource coming in another post): “Short, compact plants are easier to sell because they look more balanced in a small pot. Short stems also don’t get tangled together on the bench and are less likely to get broken during shipping; and you can stack many more flats of short plants on shelves in a semi truck.”

Flowering plants, like marigolds, have been treated with PGRs for years, resulting in small plants with blossoms that you see so widely available. But it’s only in the last few years that PGRs, specifically Sumagic, have been approved for use on vegetable plants. It’s telling that one can look in vain for testing on the safety of  individual commercial PGRs used on edibles. The fact that the Sumagic paper cited above suggests testing is needed to see if the compound can be found in the tomatoes, eggplants, and peppers from plants treated with the PGR is not only telling but frightening.

Again, if you’re buying nursery stock this planting season and want to avoid PGRs, be sure you’re buying them from a reliable organic grower. Until we know more about any risk that might be associated with commercially used, synthetic PGRs, organic gardeners will want to steer clear.

Note: In the last couple years, the U.S. Environmental Protection Agency (EPA) has decided that naturally derived liquid kelp and seaweed products must be registered as plant growth regulators (PGR). The designation seems odd to us. After all, we’ve been using kelp fertilizers on everything from our peppers to our petunias. Hopefully, common sense prevails.

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7 Responses to “Plant Growth Regulators: Safe?”

  1. Denise on February 17th, 2014 at 8:55 pm #

    Ya’ll really need to include Pinterest buttons on your pages. You share wonderful information and I’d like to be able to save it to reference later. Pinterest is about the only place I save to any more, so I’m almost in the habit of just closing the page and not bothering once I see it’s yours because I won’t remember the info, and have no way to save it for later. I think it would be good for your traffic as well….please consider adding it! Thanks!

    • E. Vinje on February 18th, 2014 at 4:09 am #

      Denise – We should have Pinterest buttons on our pages by the end of the week. Please check back!

  2. Jeff on January 1st, 2016 at 4:40 am #

    What about triacontanol? Its a PGR, farmers use it on many food crops. Its been tilled into the earth to improve nutrient uptake and increased growth.
    Sounds horrible right?!?!
    In actuality it is far from scary. Triacontanol is in alfalfa, farmers rotate crops on used alfalfa plots. Triacontanol is also in bees wax, which means its in make up and lip gloss. Sounds like a harmless natural process of utilizing nature. In fact, its even “green” because it is recycled in farmers fields.

    • Tony on May 17th, 2017 at 4:48 pm #

      Is the alfalfa being used GMO or organic?

    • Interesante. Excelente. Gracias on January 8th, 2018 at 5:36 pm #

      Interesante, excelente, gracias.

  3. Jeff on January 1st, 2016 at 4:02 pm #

    Hmmm…..I see my message on the organic natural PGR triacontanol in alfalfa was not approved to be added to your comments. Plants steroids are everywhere, in fact it is in most organic fertilizer. Its a product of the breaking down of organic material. Highest natural triacontanol levels are in alfalfa.
    So some of the information in your document is not correct and is in fact erroneous. Do you put compost on your garden vegetables?? Is it considered bad to grow healthier plants using natural organic compost? Yes, triacontanol can be extracted via non-organic methods. But this is not what I am referring to. Soaking alfalfa pellets in water with molasses allows the tea to be foliar fed to the plants giving them the triacontanol boost to increase production. Its natural, and I don’t see why your afraid of the information I have provided. I suspect it is more to promote an agenda than to provide actual facts.
    Cheers…and I bet this doesn’t get posted either.

    • David on March 24th, 2019 at 9:10 pm #

      If you stand behind what your saying, you wouldn’t be afraid to put your face on it. Also, I’m not discrediting you, but if you’re going to make claims as you are making, then maybe your should cite your sources and prove what you’re stating. Otherwise, it’s just hearsay and isn’t worth a lick. Perhaps that’s why your comments weren’t being posted. Next time, you should think about your approach and reasons why it isn’t being received as intended instead of becoming impertinent. I bet you’re too obstinate to ever take such strides.