What's the best time to start a root over rock?

Nice easy one for you here. What would be the best time of year to start a root over rock with a 1 year old Redwood seedling? I'm not sure if it's Dawn or Coastal (I'll have to check my records).
My initial thoughts are that it's either too early in the tree's development, or too late in the year to do it now. Am I right?
The reason I want to start this off as early as possible is that I have a football sized chunk of red stone from beside Loch Lomond which I would like to match up with a Redwood (see what I did there?).
I hope to create a fair sized tree which doesn't look out of proportion to the stone.
I have a humungous pot which I can use to bury the ensemble in during development as ground space is seriously limited at our house.

Ideally I'd suggest a year in a very tall pot (gutter pipe or similar) and then over the rock in spring. It is highly likely to be too small at the moment, with very fine and fragile roots, if it is only a 1 year old seedling. You need to develop long straight roots that will allow them to go around the rock and into the compost beneath.

Thanks for that Kev. I'll just go and get my screwdriver to get the drainpipe down......

However, I have a VERY hard time picturing a redwood root-over-rock bonsai.

That may be simply because I've spent quite a bit of my time (younger days) walking under these humongous, 300-foot-tall, 30-foot-wide, arrow straight trees, with no branches until 100 feet over my head.

Good point, Jim. However, the rule breaker within me has other plans......

Besides, I have spares, just in case!

JimLewis wrote:However, I have a VERY hard time picturing a redwood root-over-rock bonsai.

That may be simply because I've spent quite a bit of my time (younger days) walking under these humongous, 300-foot-tall, 30-foot-wide, arrow straight trees, with no branches until 100 feet over my head.

I don't know, Harleyrider, you might have to commission a REALLY BIG POT!

Jay

I'm still fighting the overwhelming urge to plant one in some random out-of-the-way place. The thought of some bloke standing there in the future, looking up at it and scratching his head makes me laugh.

I can just hear him now. "How the bloody hell......"

Dawn or Coastal

Dawn Redwood should be yellowing and losing their soft compound leaves soon as they are deciduous. Coast Redwoods are evergreen and more prickly, harder than Yew leaves.

That makes them Dawn then. Not only have they begun yellowing, they've gone right past that to an orangey-pink and are currently in the process of going bald!

Dear Harley,
You have a samll plant with several apical roots for distribuition over rock? So, planting with plastic film, how the Harry Tommlinson. In summer begins.