I’ve been doing bonsai for 3 years but this is my first year with collected trees. I followed Ryan’s guidance for leaving native soil and some portion of the roots untouched. All of them (5 total) went into various types of grow boxes based on size and weight. I used DE, lava and perlite as the soil added around the native soil. I applied the topdressing as prescribed (50/50 collected moss with sphagnum).
I’m struggling to understand when to water, the new soil and topdressing will get bone dry if I wait until the native soil (mainly clay) ever gets dry. Which doesn’t seem like an environment that would facilitate roots growing into the new soil. But on the flip side, I don’t want to drown the roots in the native soil before they have a chance to grow into the new soil. Ryan’s mentioned before that the capillary action should pull water into the new soil, but that doesn’t appear to be happening.
How should I manage this situation? Should I be focused more on the new soil instead of the native soil?
I’m just curious, what species are these trees?
Its a wide range and all having the same problem really. It’s a Japanese maple, Doug-fir and a juniperus virginiana.
Yea, I was wondering if any were deciduous. In my opinion it’s always far better to bare root most deciduous trees. So for the Japanese maple I would have washed out all of the field soil with a hose. Keeping field soil on deciduous collected material seems to create problems much faster than for conifers. But if the leaves are already out and growing, you’ll have to leave it til next year. Hopefully someone with more conifer collecting experience will chime in with some advice for you though.
Yeah leaves are out already. So would you recommend watering when new soil gets dry first or wait until field soil is drier?
Hi trent.strum, Although my Japanese maple (after one year), seems to be doing fine. I’m struggling with the same issue, in my case I got pumice and clay soil, any updates? how are you managing?
I have been leaning heavily on reading the top dressing. When top dressing is dry I water. From what I have been able to understand from Ryan the top dressing will pull water up through soil column to maintain a better water balance throughout. If that is the case, then relying on top dressing should be a viable strategy. So far it seems to be working, but I also tend to doubt myself when it comes to whether I am watering appropriately or not.
My advice to beginning collectors is to dig trees you don’t care about. If you can keep them alive, then move on to the nice trees you want.
For the record! Last year I bought a Japanese maple in muddy soil and pumice. I didn’t know how muddy the field soil was until I repoted this year, any how most roots growed on the perimeter and almost none on the core muddy stuff. It was in full sun, pruned the apex about 3 times and watered quite a lot, even like that it did get sun burn. This year after removing all old muddy soil and using substrate the tree is very healthy with not too long internode or big leaves… I hope this helps. 
After I repot trees I tend to put chopsticks into the soil where the stick can penetrate the older soil and new soil or near where they meet.I leave the chopstick there. I can then pull the chopstick up to see how much moisture is present in the soil. This gives me one more way to gauge how much to water or when. I find newly potted trees take up much less water than you might think based on looking at the soil surface alone. I find my self lightly watering the foliage on new trees to moisten the soil surface more often until the tree fills out the pot with more roots. As time goes by can start to rely more on soil surface to tell me whats going on in the pot because a pot full of roots will behave more uniformly than one that has areas of soil without roots pulling the water out of the soil.