There are several chemicals that are used to control growth: e.g.
Florel, Bonzi, B-Nine and Sumagic (I believe these are all trade names).
Florel is one of the oldest ones and it works by maintaining the plant
in a vegetative state (non-flowering) while the plant is being treated.
This encourages branching and helps to keep the internodes short for a
bushier plant. I haven't used the others, but there are different modes
of operation, particularly in the newer regulators.
However, Florel won't really control petunias once you stop treating
them so they can flower. Your best bet is to change the variety of
petunia you are growing to one with a more compact habit.
Can't you just pinch out the tops when young to cause branching and then use a
low nitrogen flowering fertilizer? I have the old fashion self seeding kind
in my yard and that works on them.
I pinch the tops out at least 2 or 3 times to get multiple stalks from each
plant before letting them go and don't use over a 4% nitrogen fertilizer about
once a month. I have solid masses of lavender & white flowers. This variety
still gets close to 24 inches, but that's over the whole growing season.
That works fine for a few plants, but when you have a greenhouse full
the hand pinching is labor intensive and adds significantly to the
production cost. That's why the chemicals were developed and are widely
I saw no information in the original post regarding quantity. It could
be either way. The original post asked specifically about a growth
retardant. I was actually responding to a later post suggesting Bonzi.
Not always. I worked in a greenhouse operation which had millions of square
feet under glass. We propagated millions and millions of mums each year and we
hand pinched them all. King buds had to come out and no chemical growth
retardant could do that.
You would have the same results if you just cut the petunia back. I did
something this year I never did before. The reason was wanting to see how this
new variety of petunia would do in a greenhouse setting over winter. They are
"Wave" petunias, but their millionbells type and white with dark vein throats.
Well, they are looking better than anything. I cut them back, almost to the nub
and they are setting up buds now.
I am also trying this with tomatoes. All winter I've been eating 'Roma,'
'Brandywine,' and 'Sweet Million.' I have cut the plants way back and I will
plant them after danger of frost has passed. I will be interested to see what
happens. They are all putting up beautiful new growth.
Victoria-off on a tangent, but it's early and my mind is wandering.
HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.