First-time Rootmaker User Observations

ThirdCoastBorn

Sapling
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Texas
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I used Rootmaker’s air-pruning propagation system for the first time this winter and wanted to offer my observations/notes in case they may be of help to others. Overall, I was quite pleased with the root branching exhibited for most seedlings and found the trays worth the cost vs. non-air pruning ‘control’ containers.

As I transplanted one tray yesterday and will be finishing up another this weekend, think my largest mistake was leaving them in too long; Rootmaker recommends ~2-3 months in the 32 cell trays before up-potting (starting from initial germination) whereas mine had already grown for several weeks (in standard 12 cell containers) before I got the Rootmakers and they’ve spent 3 months in them so trees are total about 4 months old. The Crape Myrtles especially became so root-dense in the containers that they begin to lose their effectiveness; it also meant more roots got lost as I combed them out.

Unfortunately, I’d long before made the rookie mistake of starting the seeds early & indoors (caught the bug last fall and wanted plenty to do over winter to keep me busy!). They were grown under 2 foot 4 bulb HO T5’s, in a grow tent with temp ~73-78F and ~50-70% humidity, with a 4” intake fan running 24/7, and gradually hardened off over a period of two weeks. The Crapes definitely did NOT like the light’s heat, hence their growth pattern.

Other thoughts:
  • Better root structure occurred in the exterior cells of the trays, presumably due to (relatively) less crowding & room for growth to the sides, as well as more exposure to air currents (interior cells being shielded).
  • Within each cell, the densest roots were at the narrowly-tapered bottom, with significantly less toward the surface. I’m guessing this is due to some combination of: More evaporation/less moisture retention at the top, greater airflow at the bottom, and possibly the amount of growth seedlings already had before going into the tray. RM recommends NOT trying to germinate seeds directly within the tray (to do it elsewhere so each cell is guaranteed to have growth), but to do so ASAP which likely means a matter of days not weeks. I’ve got yet another batch of already germinated seeds that are ~10 days old that will be going in ASAP once I’ve cleaned & sanitized them; hopefully more root branching will occur sooner/higher.
  • I was entirely unsure of what soil mixture to use -- RM itself recommends a soil mixture of either 1:1 peat:perlite or 2:1:1 bark:peat:perlite, but I know that Brent uses more a bark:perlite/pumice mix (at least for later development?) I ended up going with roughly equal portions of bark, perlite, and peat which resulted in a re-watering time frame of ~30 hours. I’ll use a bit less peat next time, both to shorten the watering schedule slightly and hopefully preclude the fungus gnats that I fought this round (we’ll call it a draw). The Austrian Pine roots were probably the poorest of all; while I’m not exactly sure how young healthy pine roots should look, I realize in hindsight they in particular were challenged by the peat.
  • I wish the trays were available in white, which would be much better for both starting early indoors (the tent’s inner reflectiveness was reduced with the black) and dealing with unseasonably warm spring temperatures (91F!). I’ll consider spray painting them for next season, unless doing so would be harmful in any way?
  • I also have the slightly larger 18-cell shuttle with removable containers, but have found it troublesome and won’t be getting another. The drainage holes are larger and somewhat oddly-placed, so I had to use ~1/4” size substrate which dries out entirely too quickly. Whereas my overall loss rate for seedlings this year has been < 10%, I’m down to 11 of 18 (40% attrition).
Hopefully this post doesn’t come across as if I’m trying to present guru expertise – I am brand new to bonsai! But I’ve read massive amounts of horticultural resources the last few months and perhaps these reflections on how I put the information into practice for the first time will be helpful to other beginners or those curious about RM specifically. Thank you for reading.
 

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River's Edge

Masterpiece
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I used Rootmaker’s air-pruning propagation system for the first time this winter and wanted to offer my observations/notes in case they may be of help to others. Overall, I was quite pleased with the root branching exhibited for most seedlings and found the trays worth the cost vs. non-air pruning ‘control’ containers.

As I transplanted one tray yesterday and will be finishing up another this weekend, think my largest mistake was leaving them in too long; Rootmaker recommends ~2-3 months in the 32 cell trays before up-potting (starting from initial germination) whereas mine had already grown for several weeks (in standard 12 cell containers) before I got the Rootmakers and they’ve spent 3 months in them so trees are total about 4 months old. The Crape Myrtles especially became so root-dense in the containers that they begin to lose their effectiveness; it also meant more roots got lost as I combed them out.

Unfortunately, I’d long before made the rookie mistake of starting the seeds early & indoors (caught the bug last fall and wanted plenty to do over winter to keep me busy!). They were grown under 2 foot 4 bulb HO T5’s, in a grow tent with temp ~73-78F and ~50-70% humidity, with a 4” intake fan running 24/7, and gradually hardened off over a period of two weeks. The Crapes definitely did NOT like the light’s heat, hence their growth pattern.

Other thoughts:
  • Better root structure occurred in the exterior cells of the trays, presumably due to (relatively) less crowding & room for growth to the sides, as well as more exposure to air currents (interior cells being shielded).
  • Within each cell, the densest roots were at the narrowly-tapered bottom, with significantly less toward the surface. I’m guessing this is due to some combination of: More evaporation/less moisture retention at the top, greater airflow at the bottom, and possibly the amount of growth seedlings already had before going into the tray. RM recommends NOT trying to germinate seeds directly within the tray (to do it elsewhere so each cell is guaranteed to have growth), but to do so ASAP which likely means a matter of days not weeks. I’ve got yet another batch of already germinated seeds that are ~10 days old that will be going in ASAP once I’ve cleaned & sanitized them; hopefully more root branching will occur sooner/higher.
  • I was entirely unsure of what soil mixture to use -- RM itself recommends a soil mixture of either 1:1 peat:perlite or 2:1:1 bark:peat:perlite, but I know that Brent uses more a bark:perlite/pumice mix (at least for later development?) I ended up going with roughly equal portions of bark, perlite, and peat which resulted in a re-watering time frame of ~30 hours. I’ll use a bit less peat next time, both to shorten the watering schedule slightly and hopefully preclude the fungus gnats that I fought this round (we’ll call it a draw). The Austrian Pine roots were probably the poorest of all; while I’m not exactly sure how young healthy pine roots should look, I realize in hindsight they in particular were challenged by the peat.
  • I wish the trays were available in white, which would be much better for both starting early indoors (the tent’s inner reflectiveness was reduced with the black) and dealing with unseasonably warm spring temperatures (91F!). I’ll consider spray painting them for next season, unless doing so would be harmful in any way?
  • I also have the slightly larger 18-cell shuttle with removable containers, but have found it troublesome and won’t be getting another. The drainage holes are larger and somewhat oddly-placed, so I had to use ~1/4” size substrate which dries out entirely too quickly. Whereas my overall loss rate for seedlings this year has been < 10%, I’m down to 11 of 18 (40% attrition).
Hopefully this post doesn’t come across as if I’m trying to present guru expertise – I am brand new to bonsai! But I’ve read massive amounts of horticultural resources the last few months and perhaps these reflections on how I put the information into practice for the first time will be helpful to other beginners or those curious about RM specifically. Thank you for reading.
Just some thoughts for consideration moving forward;)

If the holes are too big then use the method of inserting a section of PVC pipe in the middle of the pot, pour larger particles around the outside, smaller particles in the inside, slowly move the pipe up and fill with smaller particles and replant your seedling with the smaller particles. The larger particles will remain on the outside and block the holes.
Manufacturers typically suggest a one size fits all approach.
When adapting mix preferences from other growers be sure to adjust for your climate and watering practices. Also make adjustments for species. Pines like a drier mix so would benefit from less peat, less fir bark for example than some other species. We often feel that the ratio is the ratio when in fact growers modify for their particular situation and their watering habits. Later on you will make minor adjustments for the species and stage the species is at as well. Fine tuning for the difference between wanting aggressive growth and refinement. The factors we adjust include the soil mix and particle size. A nursery in the Napa Valley has a specific micro climate and specific watering system.
 

ThirdCoastBorn

Sapling
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Texas
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Thank you so much for your guidance, very much appreciated! I had tried blocking the larger holes of the 18 cell system with larger pieces of pumice to stop the substrate from draining out; seemed to work decently enough but I like your PVC pipe idea better. Regardless of whether it's due more to the container design (more airflow?) and/or that substrate, those cells still require watering ~3x/day, and on the occasions I've been late, am guessing any and all new feeder roots get killed off. The trees simply haven't grown as well as ones in the 32 cell tray or even a standard 3" pot and that's the best explanation I've been able to derive.

I know (conceptually) to customize soil mixes for my climate, but am still new enough to not know "exactly" what components might get switched when customizing something from Napa Valley to TX, especially in the context of indoor growing (I realize yet ANOTHER reason to start seeds outdoors at the right time :). TBH, at the time I loaded the tray in January, I knew almost zero about pines (still do :) so hadn't even considered they'd need a much drier mix. But operationally, it would've presented another challenge to have cells in the same tray be on different watering schedule (i.e., pines every Y hours, Crapes every X), which is one reason why RM recommends not mixing species per tray (the other being varying growth rates with different ideal lighting distance).

My PLAN (ha ha) for next year is to limit myself to two or three batches of seeds, so each will go in their own tray that can be customized exactly. Thanks again!
 
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