Coastal Redwood Young Sapling - Soil Question

Hello there!

New to Mirai and first time poster looking for some clarity. I recently (Nov. 2021) received several young high elevation coastal redwood saplings. All are about 6” tall w/ 1/8” caliper.

I’ve recently repotted them in bonsai mix (70% fir bark, 20% pumice, 10% lava) in hopes this would be good for them. Repotted in 2.5 gallon nursery pots.

Now I’m reading potting soil w/ bark would have been a better choice in terms of growing them quickly w/ increased caliper. Looking for clarity and appreciate any insight. Is my mix bad for the young redwoods?

If so, to avoid repotting them again, is it possible to slowly water in SOME potting soil/compost to help them out?

If potting soil would be better can someone explain why? I’m under the understanding that bonsai mix is superior for growing trees but maybe there is more too it!

I’m aware they should be outside but temps will drop below 20 degrees unexpectedly in eastern US zone 7a tonight.

Best regards,

1 Like

@_semper . .cool start. ANY newly repotted tree should be protected from freezing range temps. Even bringing into an unheated guarage would do.
I do not have any Costal redwoods… The mix you used should be OK. The fir bark is for moisture retention (and slow fertilizer…) required by the younger tree growth. Mimics the potting soil, but is more controlled. The pumice is for water and fertilizer retention; and lightening the mix. The lava helps drainage.
Regardless, the trees will be fine for a couple of years. Do a querry and view some Mirai videos. There are some on costal redwood. Your looking for guidence on GROWTH soil and not refinement.
My dawn redwoods( look alike, diffrent species, decideous…) and swamp cypress (same difference…) do great in 1:1:1 akadama:pumice:lava. Others use different mix. Works for me here. Im in a high mountain cold winter hot summer desert area.
Good luck!
Bonsai On!

1 Like

Thanks for the info Kurt! Will try and do some more digging for growth soils! Again thanks for such a detailed reply!

I think your soil mix as fine. You’ll find there are as many different opinions on what soil is best as there are people that do bonsai.

I think there are perks to each approach. Organic potting soil is cheaper and easy. It can definitely work. I think its harder to transition from full organic to full bonsai soil though. If you start off in a somewhat aggregate soil as you did that will make the eventual transition easier.

1 Like

Thanks I was kind of thinking the same. Did keep some native soil so to speak during the repot as well. Not very much as the root ball is so small. Appreciate your response. They seem to be adapting just fine minus one that keeps weeping in full sun. The other three don’t weep at all in full sun.

I have several collected Coast Redwoods and Bob Shimon who I bought them from uses/encourages pure akadama or an akadama/pumice blend. I currently have all of mine in hard akadama 3:1 Pumice. Since moving my redwoods from the collected soil to this akadama blend, my trees have exploded with new growth. Great airflow and drainage and very good water retention. I just started with some light feedings of organic fertilizer and find that the akadama & pumice blend provides good uptake.


I was just reading an article about Bob. I’ll keep that in mind next time these are ready for a repot!

Given the size of the containers here I’d imagine filling them with mostly akadama would be a bit expensive!