Which leads us into the ugly side of floral enhancement - synthetic PGRs and some seriously
suspicious labelling practices.
A huge market exists for products that can promote unnatural growth, albeit with an assortment
of dire consequences. Many of these products are sold over the counter and some from behind
dusty closed cupboards; few contain any genuine warning labels, occasionally stating in small
text “For growth control of container grown ornamentals only.” Commonly recognized as PGRs
(Plant Growth Regulators) these commodities are peddled by retailers ‘to stop vertical growth’
or ‘to initiate earlier flowering with heavier fruit set’. In Australia, it’s possible to register these
products with the APVMA but many manufacturers don’t bother with the effort or the expense.
Over the past century, commercial farmers have used PGR’s in a wide range of fruit and
vegetable crops but only recently are we beginning to understand the resulting health and
environmental harm. The most popular in the current market generally contain a combination
of paclobutrazol, daminozide or chlormequat chloride. When used effectively, they inhibit the
natural plant hormone gibberellins, which is responsible for cell elongation and cell division.
This limits height and internodal length. Fruit and flowers density are drastically increased and
paclobutrazol even improves mould and fungi resistance. However for all of these ‘benefits’,
there is an abundance of negatives to follow.
Firstly, the quality of the end product is drastically reduced. The impacted flow of gibberellins
also reduces essential oil and resin production, reducing the flavour and scent of fruit and
flowers. It can also result in drastic mutations to the plant. The far more worrying aspect of
these products is the damage to user and consumer health. In the United States, all three of
these PGR’s are illegal to use on plants grown for human consumption and completely banned
from sale in several states. Daminozide is listed as a human carcinogen, chlormequat chloride
has been linked with developmental problems and paclobutrazol has negative effects on the
reproductive system and causes foetal malformations in rats. Paclobutrazol also has low mobility
and low volatility so it lingers in soil and can contaminate a growing medium for years without
degrading.
Ominously, even the registered products contain industrial/technical grade ingredients that can
be just 95% purity. The remaining 5% can contain toxins, heavy metals, preservatives or toxic
adulterants. More concerning is the subversive market of unregistered PGRs with no real quality
control, labelling or adequate directions for use, but that’s a topic for another day. While the
registered PGR’s are clearly bad, there’s currently a demand for the product in the market and
suppliers will continue to meet it. If you still choose to use these products because it’s the only
way you can get that heavy harvest, please try to investigate safe dosing and flushing practices,
and relevant withholding periods, but you’ll never get the same quality harvest as a healthy
fertigation program.
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