Drainage layers. Do you use?

[Srt8madness]

One reason could be to restrict root growth more to give finer ramification instead of coarse growth.

 

[Brian Van Fleet]

If people are using “drainage layers” why, other than it “seems like a good idea”?

Once the roots have taken up the whole pot or to the point of the “drainage layer” it needs to be repotted.

Nearly 30 years of good results doing it that way. Larger particles at the bottom allows better exchange of air and water early, and space for roots later; the former drains water, the latter absorbs it.

 

[penumbra]

If people are using “drainage layers” why, other than it “seems like a good idea”?

It sounds to me, even if you use a screen to separate the growing medium and presumably the roots from the “drainage layer”, what purpose does it serve?

Once the roots have taken up the whole pot or to the point of the “drainage layer” it needs to be repotted.

If you are planting in a deep cascade pot, the entire capacity of the pot is a lot more than is generally needed by the plant. Case in point is the following Carmona. They are sensitive to root work and very sensitive to over watering. This one has not been repotted in 4 years. It may not have established itself very well if I did not have a drainage layer. As it is, it has taken 4 years for roots to finally reach the bottom. Being as this is a small plant, I did not use screen between the bonsai mix and the drainage layer as I would have done in a large pot. The drainage layer here is about 1/3 of the pot's height.
In a large cascade pot you can waste enough bonsai soil to plant another entire bonsai if you don't use a drainage layer. I like the extra weight at the bottom of a tall pot as well.

 

[Leo in N E Illinois]

Your point about a uniform particle size is really is really the key issue.

Look up rock density by particle size. It makes no difference.

If people are using “drainage layers” why, other than it “seems like a good idea”?

It sounds to me, even if you use a screen to separate the growing medium and presumably the roots from the “drainage layer”, what purpose does it serve?

Once the roots have taken up the whole pot or to the point of the “drainage layer” it needs to be repotted.

In a tall cascade pot, I separate the drainage layer with screen because it is unlikely roots will ever make it all the way down there. If the tree going into the cascade can get roots all the way to the bottom in one or two seasons, I don't use a drainage layer, simply use a uniform mix all the way.. I don't use many cascade pots these days. Small pots, at or less than 4 x 4 x 6 inches, I would most likely use a uniform mix with no drainage layer.

 

[discusmike]

No layers for me

 

[River's Edge]

I use a layer of coarser pumice in all but "Shohin" size pots! The size is chosen in relation to the particle size used in the general mix or main substrate. It varies to make sure the "drainage layer is not too different in size and also not too deep. The layer is only 1 to 3 particles deep but provides several benefits. Improved gas exchange, better drainage or escape for excess water when needed. This is important when one lives in a rain forest climate. Added benefit is the more manageable root system when repotting! Aids the root work with a good even staring point. The research on water columns in pots is applicable to situations where the layers are deeper and the difference in particle size is more pronounced. As others have mentioned it also slows the plugging of screen material over the drainage holes. Each of the professionally trained individuals I have studied with all follow this practise.
I do not view it as required but rather as an added benefit that can improve and prolong the continuing health of the tree between repots. A major issue in Bonsai care is overwatering and being left out in the rain in climates that have extended wet periods. This practice is an aid to managing both of those situations.

 

[Srt8madness]

So to summarize, it seems that drainage layer is a yes, but only very thin, and slightly larger particle than soil.

I read somewhere that the phrase drainage layer is a bit of a misnomer itself. As Mr. Corrigan alluded to, a large particle "drainage" layer will just move the water table up in the pot.

Seems like Leo's use is also less about drainage and more about volume management.

 

[Clicio]

I use a layer of coarser pumice ... This is important when one lives in a rain forest climate. ... A major issue in Bonsai care is overwatering and being left out in the rain in climates that have extended wet periods. This practice is an aid to managing both of those situations.

I´ve been using this botton drainage layer in all but the shallower pots, as I live in a tropical rain forest climate and it seems to work here.

 

[Leo in N E Illinois]

Yes, I am a no drainage layer vote.