2nd Root Over Rock - Green Japanese Maple

[BonsaiOnTheBrainTX]

Here’s my second ROR I just put together. I used a generic Acer P seedling on a limestone rock from the hill country in Texas. I was able to position it so the roots will grow down both sides into the grooves. I have one big rock left that I think I’m going to plant a Brazilian Rain Tree on. I haven’t seen many of those over rocks so hopefully it will work well.
Is it best practice to let the tree grow wild the first year to promote root growth? Or is it ok to prune as you normally would?
Thx

 

[Shibui]

Those rocks are nice. I'm assuming they are reasonably hard form of limestone. It's always a pity when you've spent years growing a ROR and then the rock falls apart. That's happened to me a number of times so now I'm more careful when selecting rocks.
Having roots down both sides of the rock is essential. With roots only on one side, as the trunk and roots thicken the tree is pushed away from the rock and may even fall off the rock.

Is it best practice to let the tree grow wild the first year to promote root growth? Or is it ok to prune as you normally would?

I prefer to allow plenty of growth. The more you let it grow, the quicker the roots will thicken and grab the rock. In practice you may need to prune occasionally and accept slightly slower root and trunk thickening though. A single huge chop at the end of growing phase will take years to heal and grow a new trunk to match the chopped stump. Often it's quicker to do some occasional pruning through the grow phase which will take longer to get trunk and roots to size but then you'll have smaller chops and therefore reduce the length of the second develop branches and heal wounds phase.
I guess it all depends what you want your ROR to end up looking like.

 

[BonsaiOnTheBrainTX]

Those rocks are nice. I'm assuming they are reasonably hard form of limestone. It's always a pity when you've spent years growing a ROR and then the rock falls apart. That's happened to me a number of times so now I'm more careful when selecting rocks.
Having roots down both sides of the rock is essential. With roots only on one side, as the trunk and roots thicken the tree is pushed away from the rock and may even fall off the rock.


I prefer to allow plenty of growth. The more you let it grow, the quicker the roots will thicken and grab the rock. In practice you may need to prune occasionally and accept slightly slower root and trunk thickening though. A single huge chop at the end of growing phase will take years to heal and grow a new trunk to match the chopped stump. Often it's quicker to do some occasional pruning through the grow phase which will take longer to get trunk and roots to size but then you'll have smaller chops and therefore reduce the length of the second develop branches and heal wounds phase.
I guess it all depends what you want your ROR to end up looking like.

Yes I think the limestone here is pretty durable. People use it for homes, retaining walls, etc.

That makes sense regarding the pruning and finding a balance depending on how you want the end result. Thanks for the insights

 

[emrylle]

I’m contemplating using a limestone rock for a ror project also. But I’m worried about the alkalinity of limestone adversely affecting my tree which prefers slightly acidic conditions. I know acer p. likes acidic soil also. Did you do anything to mitigate the effect of the alkaline rock leeching into the roots? Or is that even a consideration? Have you done other projects with limestone rocks, and if so how are the trees doing long term?

 

[BonsaiOnTheBrainTX]

I’m contemplating using a limestone rock for a ror project also. But I’m worried about the alkalinity of limestone adversely affecting my tree which prefers slightly acidic conditions. I know acer p. likes acidic soil also. Did you do anything to mitigate the effect of the alkaline rock leeching into the roots? Or is that even a consideration? Have you done other projects with limestone rocks, and if so how are the trees doing long term?

Ive never heard of that affecting a planting. But I don’t know for sure. You can use fertilizer for acid loving plants to mitigate I suppose. Or a substrate that has some acidity. So far mine are doing great!

 

[emrylle]

Ive never heard of that affecting a planting. But I don’t know for sure. You can use fertilizer for acid loving plants to mitigate I suppose. Or a substrate that has some acidity. So far mine are doing great!

I did a fair amount of research over the past week and now I feel fairly confident that the rock acidity won’t harm the plant. And like you said, a little acidity in the substrate should help.