Lava Rock in the bottom of the pot

BentBarrel

I was going to repot a couple trees that I have in large growing pots. I have some lava rock that is 1/2 inch to 3/4 inch size. I was going to put about 2 or 3 inches on the bottom of the pot to fill up the pot to move the trees further up inthe pot. I have enough soil to go all the way to the bottom but was wondering if there was any benefit or drawback to putting lava rock in the bottom several inches. I read around and didnt see anything about that. Should I do it or not?

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tachigi

How big are the pots?
How big is the tree?
What type of tree?

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malik

You know, I've read different things on this matter. One book i read insisted that water will actually travel towards smaller granules so if you placed larger substances on the bottom of the soil the water would not drain as well.

I have always read that placing a layer of largers granules on the bottom will do the opposite and improve drainage and decrease the chance of the holes being clogged.

Turth is, I would simply mix the lava rock in with the soil. That way you will have better drainage all around and you will also be filling up your pot.

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gregb

2 things; 1/2" to 3/4" particle size is a bit large for anything bonsai--that's like gravel! And 2 to 3 inches of this gravel is overkill; how deep is your pot? We try to keep the rootsystem as shallow as we can without causing danger to the health of the tree. If you're using 2" of almost 1" particle size gravel for drainage, that leaves little room for "soil". This would mean you'd need a 5 to 6" deep pot to make it work.

Let's say you have decided to use a 3" pot (deep) Let's say you'd like to have a drainage layer. I'd use a particle size no larger than 3/8" for this drainage layer and would fill the bottom of the pot no deeper than 3/4" deep with this drainage layer. You can use lava if you like.

BentBarrel

Im sorry I didnt put the dimensions for the pots. I didnt realize when I was writing the post. The pots are about 16 or 18 inches tall. The trees are 8 year old Tamarinds grown from seeds. They are about 24 inches tall and about 2 inches or so at the base (havent measured them yet). they have been potted up since they sprouted and started growing. They were given to my wife by her Grandmother before she died as tamrind candy that comes with the seeds in it. She planted 8 of them and 2 made it well. I used to just whack the tops and limbs off. One day I decided that there had to be a better way to do it and I thunked up the bonsai thing. I thought basically thats what they are. They have taper, they were raised indoors, and they are 8 years old so they have some size to them. I dont want to get them huge so that they wont be able to get out the house cause I think they would if I never trimmed them. I water them with aquarium water that gets dosed every other day with dry fertilizers.

I have to change 50 percent of the water in the tank per week to reduce the overload of ferts and reduce bio waste from the fish and plant matter. If I dont do water changes then algae will occur in a week or two after missing a water change. This water has made a lot of plants big my wife has. I never fertilize the trees with regular fertilizer because I once goofed the amount and killed all my plants on accident.

agraham

The drainage layer won't hurt but I don't think you need it in a pot that tall.Most of the water will drain a way due to gravity as long as you use anything but muck for soil.

andy

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BentBarrel

It had previously been potted with potting soil and perlite or vermiculite. I was going to repot it with about 70 percent pine bark and 30 percent lava rock (1/8 to 1/4), axis, and pumice. 1 part each. I have noticed in the past that the dirt at times stays wet for a while with the potting soil as it had started to compact. I had thought about adding some other organic sifted matter to the 70 percent.

Mcspeed

One thing to keep in mind is that your smaller soil is giong to infill the big stuff, and to some extent change he course drain layer to essentially the same as you regular mix. If all you are doing is using it to lessen the amount of regular soil than mission accomplished.

What kind of trees? 70 % seems more than a bit high for a lot of bonsai.

Thinking too that it's too tall, and will end up wetter towards the bottom, go to something shorter. Bulb pans maybe, or a grow box, 6-8" should be plenty.