Bonsai Slab Masterclass

[matty-j]

Hey AB

I have been looking around the forum and can't seem to find a dedicated thread for stone/cement/whatever slabs for planting. I would love to hear from experienced growers who can share some insight into the Do's and Don'ts, Clay wall? Appropriate soil types (did I just open a can of worms? hehe) Do they need a drainage hole? Holes for wires? What styles are best suited? The uses of moss? Planting position? Angle of the slab? Slab form, symmetrical or more natural? Texture, highly polished or rough? Tips and Tricks?

Share a photo of your own slab planting and some of the troubles you had along the way! I am sure we can all learn from this.

Cheers
Matt

[kcpoole]

they are discussed as part of the School Curriculum, but have not done any myself so take with the appropriate measure of wariness

No holes unless the tray can hold too much water
Much wall to hold everthing in and cover with moss to retain it.
Glue wire on tot he rock / slab as tie down points

Ken

[shibui]

I gave up using slabs for bonsai many years ago. I found it extremely difficult to keep trees alive let alone healthy. Slabs dry out much faster than you appreciate. Not only is the soil quite shallow but the rock (I've only used natural rock slabs, fibreglass, etc may be different) actually sucks moisture out of the soil and helps it evaporate. I just could not keep the trees alive on natural rock slabs.
Another drawback is weight. Granite is very heavy. Slabs tend to be thicker than ceramic pots. Even a medium sized slab weighs a lot more than the equivalent sized ceramic pot so you'll need some strong friends if you hope to ever show a tree planted on a slab.

I've seen some very realistic artificial slabs. Fibreglass is lighter and stronger and can be made to look very realistic. I don't think fibreglass would absorb water like stone does.
Reinforced cement can be made thinner and moulded and coloured to look like stone. Cement still sucks water out of the root ball.

[LLK]

Re: cement slabs: the post below and the videos on the IBC may be helpful. You don't have to register, unless you want to post something. See http://ibonsaiclub.forumotion.com/t2046 ... ting-slabs
See also "Creating a slab" on YouTube.
A long time ago, there was a lot of interest in cement slabs and I remember that you could reduce their weight by adding coconut fibre and sphagnum moss to the sand-cement mix; the long fibres of the sphagnum moss helped to hold the cement together. I tried, but found that you still had to make the slabs fairly thick, so they didn't look good with bonsai.
The best cement bonsai slab I saw was made by a friend in Toowoomba. He used a very rapid hardening cement, which is so strong that you can leave it relatively thin. You have to work very fast with it. It releases a lot of heat until set. I forgot the name - sorry!
I made two fibreglass slabs some years ago, with fibreglass on metal mesh, supported with 2 metal rods underneath and finished with sand while the fibreglass was still wet. I wouldn't do it again: it's a rotten job, messy, toxic and not all that cheap. The nice thing is that you can give them any shape you like and they last. One is in use right now. I gave them a 2 cm upright edge, so they hold the soil well. No trouble with watering.
Good luck!

Lisa

[melbrackstone]

There are a couple of people at the bonsai society who make pots using chicken wire and tiling adhesive. I don't know the process, but some of their freeform pots look great with natives. Can't see why you couldn't make a slab, and I'd hope it is waterproof, unlike natural stone. (I guess you could always seal natural stone too.)

Weight, I have no idea... possibly not as heavy as concrete or natural stone....but it all depends on how big.

Whether it'll cope with cold conditions and crack in a frost, I couldn't tell you, that's not really a concern here in Brisbane...

[Sno]

Hi Matty . I've started to use granite slabs ,rocks more and more .primarly because around my way they are literarily lying all over the ground . Here's a link to one I made a while ago viewtopic.php?f=129&t=18759#p190603 . i drill a drainage hole in all of them and generally use the mesh covering that hole to loop a tye down through to wire the tree down . If I had multiple trees or I want to tye the tree to the rock more securely I glue extra wire to the rock (see the link' Graham's tye down things ' ) . The moss is a problem drying out till it properly establishs its self so I tend to situate them in a shadier location than my other trees .
Cheers Sno

[SteveW]

There are a couple of people at the bonsai society who make pots using chicken wire and tiling adhesive. I don't know the process, but some of their freeform pots look great with natives. Can't see why you couldn't make a slab, and I'd hope it is waterproof, unlike natural stone. (I guess you could always seal natural stone too...

This year’s Bonai by the Beach workshop weekend will feature a demonstration and a workshop b Carole Waller on making fake rock. It will be on the last weekend in June at a venue near Port Macquarie, NSW. I'll post the brochure shortly for anyone wanting to attend and learn how to do it.

[melbrackstone]

Yes! Carole is one the ladies from the society, and I believe she's being pestered to run workshops all the time. Glad to hear you've convinced her.

[CraigM]

Needed a slab for a raft, slab is around 1.2 long by 45 wide. Internally has two metal rods and chicken wire to support. Tried a mix of newspaper and cement to try and reduce the weight, once dried coloured and applied couple coats of pot sealer.

Has been standing outside now for a couple months and no signs of cracks, key will be seeing how it survives winter and once I pot the tree up in spring and start watering. Don't expect the slab to last indefinitely, would hope for a couple seasons. Will get started on a fibreglass version over winter, who knows depending on how that turns out, might skip the cement pot completely.

[Raymond]

Nice job son! Hope it holds for ya. Post up a pic of the raft too mate, keen for a look. 1 of my favorite styles...