I think many of us here have known this for quite some time, and it has come up in older posts.

Best drainage occurs when the entire mix is more or less homogenous in consistency.

However, the author of that article doesn't quite tell the whole story. If a layer of large substrate is placed at the bottom of a pot, and then the rest of the soil mix is added to it, eventually smaller particles will find there way down and mix with the bigger stuff at the bottom. So some water will still drain normally. A true separation of particle sizes can only occur if a screen is used between layers.

The only time I used to use large gravel at the bottom of pots was to cover the drainage holes and prevent my soil mix from spilling out. But many years ago, I stopped doing that. Instead, I take a piece of toilet or tissue paper and line the bottom of my containers. It prevents the mix from spilling out and it doesn't hinder water movement. By the time the paper has decomposed, the soil mix has settled.

A simple way to test if your mix is draining well is to saturate the pot with water and let all the excess leak out. When no more water exits the drainage after a few minutes, lean the pot about 45o on it's side. A poor mix will unload more water. A good mix should let almost nothing else out.

x

Another related fallacy: adding more or larger drainage holes will improve drainage. This is not entirely true either, for the same reasons related to soil and water physics.

x

Yes, horticulture is full of myths. Maybe some day people will realize that massive phosphorus levels do not increase flowering, no plant "likes" to be root bound, misting and humidity trays do not raise humidity, and water droplets cannot burn foliage on a sunny day! But that is probably just wishful thinking.

Oh well, at least we can educate ourselves.

Penfold, you've taken all the fun out of correcting folks succulent misconceptions and cherished traditions. We might as well close this place down now. :)

Brad

No plant likes to be rootbound? Yikes! Now I'll have to pot up my sago palm.

And that bit about the humidity trays not increasing humidity, that never made sense to me ... assuming we are talking about a tray of wet pebbles underneath a pot. But I never questioned the idea of putting rocks or broken pottery at the bottom of a container. It just seems like it "has" to be true.

And thanks, everybody, for the informative responses.

I have no real clue about these things, but when I read the palm and cycad forum they seem to insist that being root-bound is beneficial if the palm is going to be grown in a pot......I wonder if you would disagree with this....I do not grow palms so do not have first-hand experience, but I like to read about things I do not grow.....like most of this forum :o) I also wonder about the humidity thing....when I run my shower (this is misting in my mind) the humidity in the room goes way up......doesn't the concept being debunked have to do with volume of the enclosure the plant is in, the temperature, the relative humidity and the dew point? I know that my plants from amazonia do far better when they are in my bathroom for the winter than when they are in the same direction facing window in a different room one floor below (the average temp is approximately the same of course since it is central heat, but not exactly the same). I have attributed this to the fact that for an hour in the morning while showers are on-going the humidity in the room goes up. I'm guessing based on the discussion above that the humidity is not actually going up so I wonder where I am wrong....guess I could get a hygrometer to check this out for myself, but that seems like overkill :o) Dan

Brad, ha, somehow I doubt we will ever run out of myths to correct and debate.

As for keeping plants root bound, there may be benefits to it in certain situations (like limiting a plant's growth or dealing with an overly water retentive soil), but given proper conditions, a plant with ample soil volume will always be stronger. I keep many of my plants root bound, but I don't expect them to thank me for it.

And the humidity issue can be proven by anyone with a hygrometer. I've done it myself. Adding massive amounts of water to a limited air space (like in a shower or greenhouse) will raise humidity, but I'm talking about hand misting plants.

Ltecato, GREAT thread!

X, Thank you for your post...great explanation ...easy to understand. I too only learned of this about 4 years ago from Al in the Container forum...even though I couldn't explain the science part to anyone I do understand the concept behind it now. Before coming to GW I too used to put rocks on the bottom of pots, believed you should use a high phosphorus fertilizer to get plants to bloom and keeping them root bound is good for plants...I know better now, thanks to several great forums on Garden Web! I've learned so much from all you smart people :o)

I suppose my only real point was to say that a myth is only a myth in certain situations and unless you know the conditions which are being explored it is tough to make global statements. Misting will (depends on volume, time of day, etc) increase local humidity which will last varying amounts of time....in the open garden it will only increase the humidity near the plant/leaves for a short period of time as the water vapor dissipates, in a closed environment it will increase it for an extended period of time. On the other hand, the water table effect that is covered above is very clear-cut :o) Dan

I just stick some old leaves over the hole in the pot. I tried that broken stuff once in a pot, then when you repot you've got that all mixed in and the roots have grown around it.
I have had to cut more holes in pots, I've found they will drain better if the holes are one the side. No matter what kind of mix you have when you get 10"++ of rain in a short period the pots take forever to drain. Regular watering isn't a problem, just days like today.
I'm always trying to lower humidity LOL! No hope there. Damprid lasts about 1 day before the little container is full. I've given up on ever owning anything leather, no matter what it grows mold. YUCK!
Tally HO!

...in the open garden it will only increase the humidity near the plant/leaves for a short period of time.

Maybe 5 seconds?

...in a closed environment it will increase it for an extended period of time.

10 seconds?

I urge you to test this yourself if you have any doubts. The problem is that humidity diffuses very quickly. The amount of water vapor delivered by a hand sprayer will diffuse in a matter of seconds. You have to raise the humidity of the entire area before the humid air will stay put. The only way a hand sprayer could have any lasting effect is in a terrarium.

This is a great topic, which pops up from time to time.
I used to follow some of these practices, too - a drainage layer of gravel, for example -
and so it is fun to revisit and to compare the old and the new.

In the Thread Old Practices, worthy application?, Tapla wrote the following:

"Repeated fallacies:
When using bloom-booster fertilizers rather than fertilizers with more appropriate ratios you should expect a positive effect on blooming.

Using a "drainage layer" at the container bottom promotes drainage.

Roots grow toward water and nutrients.

If it works in the garden, it'll work in a container.

"It works for me" (or someone the person knows), so the debate is ended.

Peat moss is in short supply and we should feel guilty for using it.

My mother has a _______ (fill in the name of the tree) that's 15 years old, in perfect health, and it's never been root-pruned or repotted.

Hyponex rocks.

If it's published in a book - it must be true.

You shouldn't disturb the roots when planting.

On sunny days, water on leaves can burn the foliage.

Never feed (fertilize) a sick plant.

Organic fertilizers are better for plants than synthetic fertilizers. ..... or the variation: Plants prefer organic sources of nutrition.

Poinsettias are poisonous!

Make sure to put wound sealer over the pruning scars.

Dig the planting hole twice as wide and deep as the rootball & backfill with rich, organic soil.

Prune back the top when transplanting or root-pruning to "balance" the root:shoot ratio.

Your tomatoes are tastier than mine because of the fertilizer you use.

Superthrive is magic - just read what it does on the label.

*Eleanor's VF-11 is good stuff - like Superthrive.

There's no such thing as a stupid question. HUH?
How about: Can I compost really really coarse material if I chop it up into small pieces first?"

*If you scroll to the bottom of the Thread, you can read a great breakdown of Eleanor's VF-11.
One really tends to step on sensitive toes when discussing Eleanor's VF-11, but the truth must be known.

Lastly, I'll link to another good Thread on root-bound plants - and why this "technique" is used.
Most of you have probably read it, but it bears repeating.

Josh

Here is a link that might be useful: Myth: This Plant Likes/Prefers to be Root-bound

Thank you, Josh! I think this stuff needs to be posted every once in a while. It's the only way people will begin to question these myths.

I agree about the VF-11 as well. Some people will insist against all logic that it is magic.

I bought an E. Flanaganii earlier this year and had to repot it. However, I couldn't find any pots that really fit it, since it had a pretty shallow root system, but I couldn't use a smaller pot given how top heavy it was. So I lined maybe the entire bottom half of the pot with rocks. Not coarse stoney material but like, rocks that were jagged and about 2-inches from side to side on a flat surface.

I didn't do this to improve drainage but rather because I wanted to reduce the amount of moisture-holding substrate. I have no idea if this actually serves that purpose. It doesn't seem to *worsen* drainage, but drainage wasn't what I was focusing on originally anyway. Just a way of essentially reducing pot volume.

Whatever the 'shocking truth' may be, whoever claims that NO plant likes to be rootbound has not grown palms for a living. Cycads do not like to be rootbound, though they tolerate quite well in general, and unfortunately many group palms and cycads together thinking they need the same things. But after growing palms for many years, and being in contact with numerous professional growers, I have discovered independently, and had it corroborated, that many (not all) palms LIKE being root bound no mater what the know-it-all nay-sayers say. They grow faster, better and shock less when moved in the rootbound state (though there is obviously a limit to being root bound... if there is NO soil in the pot, that is obviously not good).

Keeping a plant root bound may improve growth in some cases, but that does not mean the plant prefers to be root bound. It just means the grower has chosen to manipulate pot size rather than soil type in order to maintain proper soil moisture. With a proper soil, any plant will thrive in a large pot, and be stronger for it. This does not, however, mean that all plants should be overpotted. Sometimes convenience or desired growth habits trump a slight increase in plant vitality.

The link explains it in much more detail.

I purposely overpot some plants, but I do so with the experience and knowledge that the thick layer of rock at the bottom of the pot, along with the screen, compensates admirably for it.

Love the posts in this thread - just right for a Tuesday.

I'm notorious for overpotting, with our long growing season if I don't, depending on the plant, I may be repotting it several times in a season. Some I used to underpot to keep them from growing, that really doesn't work so I've given it up, they just send roots through the drainage holes.

Small pot = death at my house. Except the bonsai and I don't mess with them. :)

Josh, thanks for the VF-11 bit, some people will bite your head off over that stuff. Silliness. The way hoyas grow down here I don't want to give them ANY fertilizer!

I don't know about palms liking to be potbound, mine are all much happier in the ground, there are several types in the yard, all took off once they were planted. Cycads are the same, took the sago out of a huge pot and in 1 year it doubled what it took 20 years to grow in a pot. I have to agree pot grown palms transplant better than those grown in the open ground, but I think that is more related to damage to the roots on digging. Gonna plant more palms this weekend, they are my newest addiction.
Tally HO!

In a closed environment the humidity will stay elevated for an extended period of time....terrarium? Greenhouse? The problem with myth-busting is that you can not choose your conditions....it should be true for all conditions or you have not busted a myth....you have simply commented on one particular situation.....Not trying to be pain, just trying to say that putting water into a hot (preferably), closed environment increases humidity and the duration of time is dependent on many factors. So, if you are using a closed environment to grow your plants then this should not be considered a myth in my opinion, but again, I am not a scientist that has studied this.

With regards to high phosphate content of fertilizer and blooming....I will toss this out for discussion. If you have a look at the International Aroid Society web pages under the genus Amorphophallus and look at fertilizing these oddball plants you will see that the worlds expert suggests using a "high" phosphate fertilizer such as 15-30-15 (many of the best growers use this phosphate level or even higher) to more rapidly increase tuber growth. Given that tuber size is directly proportional to production of an inflorescence then one could argue that high phosphate increases flower production since it increases the size of the "plant" which in turn increases the likelihood of flower production. So, does this mean that higher levels of phosphate increase flower production? It depends on your way of looking at the subject I suppose. I do grow Amorphophallus, but have never done any sort of real experiment to look at this. Curious to what everyone thinks about this subject :o) Dan

Dan,

I get what your saying about humidity. Technically, hand misting does raise humidity. But it diffuses so quickly and completely that you'd never be able to measure the increase beyond a few seconds. Terrariums and pressurized greenhouse mist systems operate on a whole other level, and are not what I was referring to. Perhaps I should have been more specific. People frequently recommend hand misting or using humidity trays to create localized humidity in homes, or even outdoors, and this is the nonsense I was pointing out.

As for phosphorus, I find that even the experts in horticulture frequently rely on word of mouth and personal experience when it comes to growing techniques. There is no scientific basis for high phosphorus levels, though. Studies are done on plant tissue compositions and I don't know of any that have ever found a plant that absorbs more phosphorus than either nitrogen or potassium. Phosphorus is always the smallest number by far.

Hi penfold, I agree with what you are saying completely, just wanted to clarify.....I never use humidity trays or anything of the sort as I think they would be silly in all honesty, but I'm pretty sure my plants in my extended bathroom appreciate the increased humidity caused by the shower so if people realize this it may be helpful in terms of growing plants of a similar ilk.

I know that all of the analysis of bulbs agrees with this and I do not know if the leading experts in the world of tuberous aroids have conducted this type of research. The person who has been responsible for naming most of the worlds species and is now doing all the genetic analysis to reorganize the various plants into their correct genus may know so I guess I should ask him....as you say, could be an old wives tale that has been passed down for the past quarter century :o) Dan

The high phosphate issue has to do with it inhibiting the absorption of other nutrients by chemically locking up other elements in the soil. Phosphate apparently is not needed in high quantities for it to have a positive effect.

For all we know, it's just as likely that a high P stresses the host plant because it cannot utilize other nutrients, and that might be what induces flowering.

Independent university-based research (don't have the reference now, but it does exist) has determined that an ideal N-P-K ratio is about 3-1-2, regardless of whether the goal is leaf growth, flowers or root development.

x

Technically, hand misting does raise humidity. But it diffuses so quickly and completely that you'd never be able to measure the increase beyond a few seconds.

If you spray in the air and not on the plants, I guess?

X: Everytime you post something, I learn something new..Thank you and thank you all for this thread..

I did notice that when I supply no heat to a plant room and group many plants together, it is the highest humid room in my home all winter..It can read 50 on my hygrometer on any givin very dry cold day outside, while the rest of the home reads 30, and when I mist all my plants to get the dust off, the hygrometer can read as much as 80 for the entire day..Once the heat goes on, even misting can't raise the humidity in that room, in fact it drops..I think it makes a wet mini micro climate for the plants surrounded by that water or being sprayed until the leaves have dried off..

Maybe putting a 4inch potted violet on top of pebbles in a 12 ich saucer sitting on stones with water surrounding it might provide some local humidity for that individual plant.No?

Mike

I have a Red Sealing Wax Palm (Cyrtostachys renda) which requires high humidity at all times. I keep it indoors for about 7-8 months out of the year. When the heating is on in the house, humidity drops quite low. What I do is coat
the leaves with anti-stress 2000, an anti-dessicant. This plant coasts through the entire winter without any blemishes on the leaves despite the very low ambient humidity.

x

I have a blechnum gibbum that I don't really do anything special for indoors during the winter. It just gets really brown and shrunken looking. Once I move it outside in the summer, it looks fine, though.

Unfortunately I'm moving to an apartment soon and loosing my porch so I THINK it's time to get a terrarium since I don't think a fern would take kindly to an anti-dessicant.

X; Do you have a sunroom, or are all your plants scattered about the home and in front of windows? You have an amazing ability to grow just about anything..

Have you ever posted a picture of it? I would love to see it..The anti-dessicant you speak of, is it good for many other tropicals that hate low humidity and where do you purchase it?

Thank you

Mike

I have a Red Sealing Wax Palm (Cyrtostachys renda) which requires high humidity at all times. I keep it indoors for about 7-8 months out of the year. When the heating is on in the house, humidity drops quite low. What I do is coat
the leaves with anti-stress 2000, an anti-dessicant. This plant coasts through the entire winter without any blemishes on the leaves despite the very low ambient humidity.

x

Mike,

I infer yes.

X,

The Department of Redundancies Department has a letter for you...and I'd like to see this palm that's used in the capture of red seals.

You are misinformed...the Palm doesn't capture seals, it simply denudes them.