Houseplants forum→Fluoride toxicity

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BonsaiBoi
Jun 10, 2020 9:33 AM CST
Hi all,
First post! I have a dracaena that I recently repotted in basically 80% perlite, 20% compost (I.e. growing almost hydroponically). It struggled straight away, dropping a fair portion of its lower leaves, with the rest getting brown tips.
THEN I read you shouldn't use perlite as it can cause them fluoride toxicity. Does this look like that?
If so, Should I repot again without perlite? I'm reluctant to disturb the roots a second time, but worry I have no other choice. The alternative is to keep watering it, hoping the fluoride dissolves and washes away.

Any help appreciated!
Thumb of 2020-06-10/BonsaiBoi/e0f4a6
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Name: Will Creed
NYC
Prof. plant consultant & educator
Image
WillC
Jun 10, 2020 2:34 PM CST
Welcome! Fluoride in tap water is not concentrated enough to be a problem and perlite used as a soil amendment to make potting mixes more porous is also not a problem. But 80% perlite as a potting mix probably is. I have never heard of anyone using so much perlite for potting.

If you recently repotted and left the original rootball mostly intact, then you may be able to gently remove most of the potting mix you added and replace it with a normal potting mix.
Will Creed
Horticultural Help, NYC
www.HorticulturalHelp.com
Contact me directly at [email protected]
I now have a book available on indoor plant care
Name: Al
5b-6a MI
Image
tapla
Jun 24, 2020 1:06 PM CST
Hi, BB - the problem with fluoride is, it's accumulative in tissues. IOW, once it's there, it's there for good ..... or until the plant sheds those of its parts in which the fluoride has accumulated. Fortunately, it's not mobile in the plant. The older the leaf, the more likely it will be to have been affected by a fluoride toxicity, so the level of fluoride in your drinking water is only one factor affecting toxic reactions to the compound.
To avoid it, try to use some form of deionized water - distilled, rain water, snow melt, dehumidifier/air conditioner condensate, or best - water that's been run through a reverse osmosis filtration system, which is what I use for plants and drinking water. A small system costs about $200 and can be installed in a half hour (by you).
You have other issues that signal you're likely confusing cause and effect, i.e., transitioning a dracaena to some form of water culture is bound to be met with protest. They don't like wet feet, or, at a bare minimum, they cannot transition back and forth from a root environment that cycles between saturated and appropriately aerated. Most growers believe perlite is the king of aeration, but it's not. Soil particle size is what primarily drives water retention, so as long as you have enough compost to fill all the space between the perlite particles, the perlite does almost nothing to promote aeration, so you're likely trying to grow in a substrate with <10% air porosity, and it's going to be difficult to make that fly.
My suggestion would be to bite the bullet and repot into something that holds very little or no excess water. It is SOO much easier to grow proficiently when you're not required to fight your soil for control of your plant's vitality. If I was growing a dracaena, this is what its feet would be in:


Thumb of 2020-06-24/tapla/33c93e
Al
[Last edited by tapla - Jun 24, 2020 1:07 PM (+)]
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BonsaiBoi
Jul 5, 2020 12:59 AM CST
Hi guys, thanks for the replies and sorry I didn't reply, I was expecting an email notification!
The soil is definitely not holding on to water, I'm watering every 1-2 days in the greenhouse! I've been using rainwater (praise the heavens).

I've left it in the perlite, and am still seeing major browning of the lower leaves but the plant as a whole seems pretty healthy, so I'm going to stick with it.
Thank You!

BonsaiBoi
Jul 5, 2020 1:00 AM CST
tapla said:Hi, BB - the problem with fluoride is, it's accumulative in tissues. IOW, once it's there, it's there for good ..... or until the plant sheds those of its parts in which the fluoride has accumulated. Fortunately, it's not mobile in the plant. The older the leaf, the more likely it will be to have been affected by a fluoride toxicity, so the level of fluoride in your drinking water is only one factor affecting toxic reactions to the compound.
To avoid it, try to use some form of deionized water - distilled, rain water, snow melt, dehumidifier/air conditioner condensate, or best - water that's been run through a reverse osmosis filtration system, which is what I use for plants and drinking water. A small system costs about $200 and can be installed in a half hour (by you).
You have other issues that signal you're likely confusing cause and effect, i.e., transitioning a dracaena to some form of water culture is bound to be met with protest. They don't like wet feet, or, at a bare minimum, they cannot transition back and forth from a root environment that cycles between saturated and appropriately aerated. Most growers believe perlite is the king of aeration, but it's not. Soil particle size is what primarily drives water retention, so as long as you have enough compost to fill all the space between the perlite particles, the perlite does almost nothing to promote aeration, so you're likely trying to grow in a substrate with <10% air porosity, and it's going to be difficult to make that fly.
My suggestion would be to bite the bullet and repot into something that holds very little or no excess water. It is SOO much easier to grow proficiently when you're not required to fight your soil for control of your plant's vitality. If I was growing a dracaena, this is what its feet would be in:


Thumb of 2020-06-24/tapla/33c93e
Al


Can I ask what's in your soil mix? Thanks :)
Name: Al
5b-6a MI
Image
tapla
Jul 5, 2020 1:12 PM CST
That is what others have dubbed the gritty mix. The starting point recipe consists of:
1 part screened Turface MVP or Allsport
1 part screened #2 Gran-I-Grit or #2 cherrystone
1 part screened pine of fir bark


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The white material is crushed granite. The tan material is Turface - a clay product baked at high temperatures so it's hard and stable. Disregard the medium at the top - that's the soil in my raised beds



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Any of the bark in this image would work. At the top is prescreened fir bark, what I use when I can get it. If I cant, I'll screen the fines out of the products at 3, 6, 9 0'clock to 1/8-3/8" and use that. This medium (gritty mix) is especially well-suited to trees, succulents, and other plants you might want to repot less often than every other year. The soil in the middle is what the 5:1:1 mix looks like, dry. That's also an extremely good medium - much more productive than what you might expect from a providor of bagged substrates.

The reason for screening: I've been studying and tinkering with container media for 30 years. When soil particles are small (peat, coir, compost, composted forest products, sand), they hold water in the spaces between soil particles. This water is very limiting and disallows plants from any hope of reaching as much of their genetic potential as possible. It kills roots at best, and causes infection any of several fungal pathogens that thrive in water-retentive media. The gritty mix doesn't contain particles small enough that water is held between soil particles. Water is held on the surface of particles, in the internal pores of particles, and at the interface where particles contact each other. This eliminates entirely the constant cycle of death and regeneration of the finest roots that accompanies use of media too water retentive. All of the energy needlessly spent on replacing roots killed by poor media would otherwise have gone to important plant functions like increasing the plant's living mass, more stored energy to help cope with off season doldrums, defenses against pathogens and insect herbivory, and eye appeal.

Al

BonsaiBoi
Jul 10, 2020 1:22 AM CST
Thanks talpla, great advice Thank You!

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