RAISED BEDS

[August44]

I am going to install 1-2 raised beds for bonsai use. I will buy the metal ones and thinking about the ones Vego Gardens has that are 32" tall. Way better on the back. Not sure I can build ones for any less as they are 40% off right now. Thinking about filling the bottom half or better with some nice black lava that the local nursery has. It is 1/4'-1/2'. Then the top half with a good potting soil and perlite or pumice. Any advice, thoughts would be appreciated.

https://vegogarden.com/collections/...tra-tall-9-in-1-modular-raised-garden-bed-kit

 

[Gabler]

Wouldn't the lava be counterproductive? Just use rich garden compost and/or high quality topsoil all the way down.

 

[August44]

Wouldn't the lava be counterproductive? Just use rich garden compost and/or high quality topsoil all the way down.

I'm not sure what you mean by "counterproductive". Pls explain that for me. I have no rich garden compost, but the nursery has bulk compost that is pretty fine, as in very small particles and I worry about that not draining well. High quality potting soil like happy frog is around but expensive here.

 

[Gabler]

I'm not sure what you mean by "counterproductive". Pls explain that for me. I have no rich garden compost, but the nursery has bulk compost that is pretty fine, as in very small particles and I worry about that not draining well. High quality potting soil like happy frog is around but expensive here.

Growing in the ground, you don't want to use loose bonsai substrate, since the soil is already presumably well-drained. In waterlogged soils, you can also use raised beds to promote drainage, since the raised bed will effectively increase the depth to the water table. The raised bed itself is what's promoting the drainage. If you put a layer of lava at the bottom, you risk creating a perched water table and literally undermining the benefit of the raised bed. You want the soil in the raised bed to be contiguous with the soil below, so the effective depth is greater.

 

[Kevin1968]

About to build one myself. Just following for now.

 

[Maiden69]

Sooo... I have pine bark on my beds because I don't have access to pumice. You are in Oregon, plenty of pumice available. Forgo all the garbage organic crap in potting soil, compost, etc and use 100% pumice. Unless you plan on planting them without any bag or Anderson flat, pumice is the way to go. All you need is a substrate that holds some water for the escape roots to grow through that will allow you to remove the tree easily.

If you are just going to plant the trees without any "root restriction" then I guess amended top soil would be ok. No need to add a lava layer at the bottom. Look at some of the posts by Frank @River's Edge , I think he uses substrate on his. It makes it so much easier when the time comes to pull them out and clean out the roots.

 

[jeremy_norbury]

I cannot believe that these are the cheapest raised bed solution.

 

[Kevin1968]

@Maiden69 what are those blocks called for the corners? I cant find them here so far.

 

[BrianBay9]

@Maiden69 what are those blocks called for the corners? I cant find them here so far.

You mean these?

Oldcastle 7.5 in. x 7.5 in. x 5.5 in. Tan Brown Concrete Planter Wall Block 16202336 - The Home Depot

Reinvent your garden with the Oldcastle Planter Wall Block. This functional wall block allows you to easily create a raised garden bed, border or even outdoor furniture. Simply stack and link the blocks

www.homedepot.com

 

[Maiden69]

@Maiden69 what are those blocks called for the corners? I cant find them here so far.

https://www.lowes.com/pd/Oldcastle-Planter-Wall-Tan-Retaining-Wall-Block-Common-6-in-x-8-in-Actual-5050-in-x-7-75-in/1001156396

This work with treated 2"x6", remember to get some .375" thick rebar to drive down the center to anchor them, they will move with time if you don't. If you stack them get some .5" thick rebar, and drive at least 18" into the ground.

 

[Kevin1968]

Lowes has them in stock here, have to order through Home depot.

Thank you guys.

 

[August44]

Growing in the ground, you don't want to use loose bonsai substrate, since the soil is already presumably well-drained. In waterlogged soils, you can also use raised beds to promote drainage, since the raised bed will effectively increase the depth to the water table. The raised bed itself is what's promoting the drainage. If you put a layer of lava at the bottom, you risk creating a perched water table and literally undermining the benefit of the raised bed. You want the soil in the raised bed to be contiguous with the soil below, so the effective depth is greater.

Hmmm, interesting. So along those lines, do you not put a drainage layer in the bottom of your bonsai pots when you plant up a tree or should the soil be all the same top to bottom in your opinion?

 

[Gabler]

Hmmm, interesting. So along those lines, do you not put a drainage layer in the bottom of your bonsai pots when you plant up a tree or should the soil be all the same top to bottom in your opinion?

Everything I've read about hydrology would indicate that you should use the same substrate throughout the pot, with a very thin layer of sphagnum moss or similar top-dressing to conserve moisture at the soil surface.

 

[Maiden69]

So along those lines, do you not put a drainage layer in the bottom of your bonsai pots when you plant up a tree

verything I've read about hydrology would indicate that you should use the same substrate throughout the pot

I don't use a drainage layer, all the videos that I have seen from Japan very rarely use it. When they use it, it is the same substrate, just slightly larger. Ryan uses the same substrate minus the 1/16" particle on most repots I have seen.

 

[BrianBay9]

Here's a mistake for you to avoid. I put some raised beds under mature coast redwoods and the redwoods filled the beds with roots from the bottom, crowding out the plants I intended! Never anticipated that.

 

[Maiden69]

Here's a mistake for you to avoid. I put some raised beds under mature coast redwoods and the redwoods filled the beds with roots from the bottom, crowding out the plants I intended! Never anticipated that.

I always use a double layer of weed-control fabric and wrap it around the sides of the bed. That way you don't get anything growing in, or any of your trees growing out of it.

 

[JeffS73]

How you plant in to the grow bed can make a difference, if you plant direct into the grow bed a compost is probably fine. I had trees in fabric pots with a loose pumice and bark substrate, then planted these flush in the growbed with compost. Over winter, the more open soil in the pots got flooded, and held onto the water, v bad for roots. Now I've got the same pots on the surface, a lot happier, escape roots can head down and do their thing, the main rootball drains properly.

 

[Shibui]

Raised beds are already way better drained than any surrounding soil because they drain by gravity. Extra drainage is not required and may even be counterproductive as you will need to water way more often just to keep roots hydrated.
'Drainage layer' has been debunked long ago and is no longer recommended by many growers. In some circumstances it can even lead to perched water table and cause more problems.
As can be seen from the comments above there's a range of problems associated with combining different soil types in pots or grow beds. Hydrology does not always work as simply as the uninitiated think.

 

[Maiden69]

How you plant in to the grow bed can make a difference, if you plant direct into the grow bed a compost is probably fine. I had trees in fabric pots with a loose pumice and bark substrate, then planted these flush in the growbed with compost. Over winter, the more open soil in the pots got flooded, and held onto the water, v bad for roots. Now I've got the same pots on the surface, a lot happier, escape roots can head down and do their thing, the main rootball drains properly.

That is because you planted them flush with the soil level. I had my trees in pouches of only inorganic substrates surrounded by pine bark and mulch. Never had an issue. This is also why I am against using potting soil or solid compost. Because if you’re a pouch, the water will drain too slow out of it. So far in 3 years using the pouches I have not had any issues with roots.

You need a substrate that will maintain humidity but not log on water. Water needs to drain out of your surrounding soil as fast as your pouch or pot.

 

[August44]

Maybe I need to clarify something with what I meant by "drainage layer". A drainage layer to me is 5/16"-1/2" pumice and most of the above substrate is pumice also but 3/16"-1/4", so I'm using the same substrate just different sizes. Maybe some of you were thinking I was using a different substrate all together for drainage. Not sure that the larger size for drainage is a good idea. I do understand now that the substrate needs to be the same top to bottom, so maybe I need to stop the large substrate for drainage thing.