Fresh air gets no credit, it's always humidity

Tiffany, purpleinopp GardenWeb, Z8b Opp, AL(8B AL)December 11, 2013

Professional indoor grow operations always have fans blowing to keep air moving, circulated. Such a structure isn't hard to keep humid because the huge amount of foliage and moist soil provide plenty of that. I've never tried to artificially provide humidity (terrariums notwithstanding) but have been running a ceiling fan on low the past few winters while plants are inside. I don't have any science-ish links to point to, but by gut instinct it makes sense to me. There's also the somewhat selfish thought that if these plants are producing oxygen, I want it flowing around me as much as possible.

A huge part of the difference between being outside vs. inside is wind blowing most of the time (except on the hottest of days it seems, right? LOL!) I don't even think it's possible for air to be completely still outside, even if we can't feel enough movement to provide any relief.

The furnace coming on will definitely move the air around, but if it's not necessary for it to come on often, or if one doesn't use a central blowing system, indoor air can really stagnate. Ever get lost in thought looking at dust motes in a shaft of light on a sunny morning or afternoon? There's tiny particles of stuff just hanging there, hardly moving.

There's the gentle drying effect that moving air has on soil/leaves to consider, and one could also wonder if the humidity of a large collection of indoor plants is best 'on the move' or stagnating around grouped plants. IDK.

So I guess I think it makes a positive difference worth the $3 or whatever it costs to run a ceiling fan on low for a month. I think that figure's probably pretty generous. But anyway, what are your thoughts on air movement? Do you think humidity has undeservedly stolen the 'advice show?'

Were you just fine NOT thinking about it and now feel burdened? Do you think I should use more free time fixing more interesting dinners than typing crud like this? Say that stuff too if you want, it's probably true.

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I believe in fresh air. I think the movement across the leaves makes the plants feel sexy so they will want to bloom.

    Bookmark   December 11, 2013 at 6:17PM
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Well Purple, I can't say whether your dinners lack interest or not, LOL! But I do enjoy your thought provoking posts. I would think that any air movement around indoor plants would certainly be a plus, and if I had a ceiling fan over mine, I would definitely use it. Isn't it the wind which strengthens the stems of young growing plants, and helps prevent mildew from setting up shop on susceptible species? I run our ceiling fans year round in our house, but unfortunately none are close enough to the "plant room" to help...perhaps it's something I should consider, now that you mention it!

    Bookmark   December 12, 2013 at 2:13PM
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Tiffany, purpleinopp GardenWeb, Z8b Opp, AL(8B AL)

Interesting, and an optimistic thought, Phal!

Keke, resistance to wind does necessitate a stronger stem. Excellent point. CF on low doesn't seem like much wind but it's got to be more strength-inducing than none at all.

    Bookmark   December 12, 2013 at 4:43PM
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Purple, I tend to run my ceiling fans on low most of the time. I think plants benefit alot from air movement. I once went on vacation and we turned our air conditioner like on 74 degrees. When I returned a black fungus was all over several plants :( I immediately started treating them with fungicide and put them outside. I was afraid to leave them outside while gone because of rain/storms.

They eventually recooperated. But next time I will at least leave one fan running on them !!

    Bookmark   December 13, 2013 at 12:16PM
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albert_135(Sunset 2 or 3)

One of he longest words in horticulture has to do with the relationship between movement and the strength of stems. I will try and find the word. It starts with a ''t'' i think.

Mike, Dec 16th below came up with the word. Thigmomorphogenesis - Wikipedia, the free encyclopedia

This post was edited by albert_135 on Tue, Dec 17, 13 at 20:04

    Bookmark   December 13, 2013 at 4:25PM
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rhizo_1 (North AL) zone 7

Circulating fans are used in greenhouses to encourage evapotranspiration in an atmosphere saturated with moisture. Without the fans, plant growth can stall, something that no grower wants to see happen.

The evaporation of water vapor from the leaf surface drives the transpirational pull of moisture from the stomata all the way to the root tips. Without it, root rot can occur.

Brisk air movement can also move spider mites around as well as powdery mildew spores (which are carried by wind rather than water). Growers, however, will consider that the benefits of evapotranspiration outweigh the possibility of the rapid spread of mites or PM.

    Bookmark   December 14, 2013 at 4:14AM
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paul_(z5 MI)

Particularly in terraria, air movement is often a "must". (Something many folks find out the hard way.) Humid, stagnant air creates an optimum breeding ground for many molds/fungi. Air movement can make a world of difference.

    Bookmark   December 14, 2013 at 11:12AM
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terrene(5b MA)

I have never thought about the air moving around the houseplants, but it's an interesting idea.

I'm dying to know what the "t" word is!

    Bookmark   December 16, 2013 at 6:45PM
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By the way, am a fan user too...Mine are always left on 24 hours a day. A ceiling one and two floor fans blowing the undersides of my plants...I would be lost without them.


    Bookmark   December 16, 2013 at 7:51PM
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How many times are we warned about air movement on our not to put our plants in jeopardy by placing them where direct air movement from open doors, windows, furnace registers....etc....can cause soil temperature to change abruptly; possibly drying out the soil faster than we would have them we protect them from such air movement.
Now, in these messages, I read people actually planning air movement by placing fans above them, around them, and otherwise doing exactly what they don't need.

What is the intent? To say that a plant needs air movement--so spider mites don't just plain silly....they land on plants in the most hidden places and begin to suck their juices.
You want to defeat them.....try misting the plant and while you are at it....move the plant to a distant space away from other plants....spider mites thrive where they can infect other plants.
Instead of air movement, try giving the plant something the spider mites don't like.....water spray, then a dust with lime sulfur, dusting sulfur or petroleum oils and keep them isolated. Every 7 days, spray them again for 21 days...after that, keep a vigil....and stop trying to waft air over them.

    Bookmark   December 19, 2013 at 11:49AM
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rhizo_1 (North AL) zone 7

Goren, you need to read more carefully....and then put your thinking cap on. :-)

Drafts from an open window or heating vent are not the same as creating air movement. Simple air circulation is almost always of benefit to plants.....inside and outside. Do some quickie research on the subject.

I beieve that you've completely misinterpreted my statement about spider mites. I never said that air movement prevents spider mites from landing....that would be silly, wouldn't it?

And I wish that you would stop mentioning lime sulfur and oil applications in the same breath. Someone might think that it's okay to apply them at the same time or within a few days of each other. Any green plant could be defoliated or worse from that combination. You've made that suggestion before.

    Bookmark   December 19, 2013 at 2:11PM
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Tiffany, purpleinopp GardenWeb, Z8b Opp, AL(8B AL)

I'll answer the questions I can, Goren.

"put our plants in jeopardy by placing them where direct air movement from open doors, windows, furnace registers....etc....can cause soil temperature to change abruptly;"
Gentle movement from a ceiling fan is not in the same category and has no effect on temps except to make them more even (from top to bottom in a room.)

"possibly drying out the soil faster"
Rhizo mentioned this as a factor of why a greenhouse operation would increase air movement. Drying fast is good, though a ceiling fan is a much less brisk blast of wind than the big fans I've seen in greenhouses, so the drying effect would also be less.

"What is the intent?" To reduce air stagnation, increase evaporation as mentioned, to provide slight wind resistance so plants aren't so weak/floppy. In my specific case also, so all of the heat isn't collecting in the upper parts of rooms and that it moves evenly through the house. So I have the fan on anyway whenever the windows are not open, even if there are no plants inside.

"To say that a plant needs air movement--so spider mites don't just plain silly....they land on plants in the most hidden places and begin to suck their juices."
I agree but don't think that was said. What I remember reading above is that a fan could spread them more quickly.

"misting the plant" I'm convinced this practice offers far more potential for harm than good.

"water spray, then a dust with lime sulfur, dusting sulfur or petroleum oils" I don't get leaves wet while plants are inside, although gentle air movement from a ceiling fan on low would help them dry more quickly if I did, lessening the potential for surface pathogens to cause problems described in the link in the last paragraph.

A very brief google of "PH of lime sulfur" leads to the conclusion that I don't want to put this stuff on leaves. I've never heard the advice about petroleum oil on plant leaves before. What would a plant look like covered in dust and oil? IDK but sure I don't want it in my house.

Spider mites can be rinsed away in a shower if they are spotted.

    Bookmark   December 19, 2013 at 2:24PM
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AsarumGreenPanda(z6 MA)

I'm a firm believer in:

1. the benefits of gentle ar moevement around my plants; I keep a ceiling fan on low all the time, too

2. the benefits of your posts, purple--they're interesting, ,thoughtful and thought-provoking. Thank you.

Phal_pal, you made my day with that explanation ;)


    Bookmark   December 19, 2013 at 5:58PM
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rhizo_1 (North AL) zone 7

Purp...though I'll admit that Goren gets on my last nerve (lol), I will explain about the petroleum oil. He/she is neglectful in not using the term "horticultural oil " instead of petroleum. Most hort. oils are refined petroleum oils. They have emulsifiers that enables them to be diluted with water and are barely detectable on plants.

We use oil sprays for a variety of plant problems.....usually outside. Commercial hort. oils are considered organic and very safe to use as a first resort against a wide variety of outdoor insect pests and their eggs.

However, one MUST never mix lime sulfur (which is applied as a spray) within a month's proximity of an oil application or you'll fry the foliage. To recommend these products for houseplants is unwise, at best.

As an aside for ceiling fan the winter, they are very helpful in making our homes more comfortable. Simply reverse the direction that the blades are turning so that they move the warmest air off the ceiling and back down into the rest of the room. We keep our fans on low all winter. You won't feel a breeze since the blades are bouncing off the ceiling.

    Bookmark   December 19, 2013 at 10:33PM
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Tiffany, purpleinopp GardenWeb, Z8b Opp, AL(8B AL)

Very helpful explanation to someone who doesn't have any plant products. So the advice wasn't as unusual as I thought, just the wrong terminology (which is suspicious for being incorrect regurgitation of info, not genuine experience.) I've heard of neem oil many times.

Another excellent point about fan direction. I never remember they do that. I bet our ceiling fan has always been on 'blow' instead of 'suck.' TY, Rhizo!

    Bookmark   December 20, 2013 at 8:58AM
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paul_(z5 MI)

You are coming across as both belligerent and woefully ignorant, Goren.

Commercial greenhouses and many (if not most) hobbyist g/hs make use of fans and have been for who knows how many years. If air movement was truly detrimental to plants, don't you think they would have realized that by now? For that matter, if air circulation was inimical to plant life, there would be a planet full of unhealthy/dying plants outside our doors and few to zero healthy ones.

As one who has started quite a number of garden plants indoors from seed, I can say from experience that seedlings grown exposed to some air movement typically demonstrate sturdier stems than those that have not.

Furthermore, I have grown plants in terrariums for a decade or so now. In stagnant, humid conditions molds/fungi abound -- and in a manner detrimental to most plants. Fans placed inside the terr, go a long ways to eliminating this issue. Again, demonstrating that it is beneficial for the air to circulate.

No one said it is a good idea to place plants where they would be subject to draughts of cold or hot air. That is indeed something to be avoided -- at least for the majority of plants. Next time, please take the time to READ what was actually written and think your statements through before posting.

    Bookmark   December 20, 2013 at 5:21PM
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