It is a official query. My grasp Shinji Suzuki by no means used lava (aka scoria), preferring simply akadama and pumice.
On getting back from Japan in 2006 I continued utilizing the akadama / pumice combine and have all the time had sturdy, effective root progress with dense root lots.
A number of lava tales have caught with me over time. Joe Harris III reported very excessive ranges of boron in lava at Iseli Nursery in pots with poor root progress. David DeGroot then had root progress points, and a lab discovered what they known as “poisonous ranges” of boron traced to the lava within the combine. More moderen lava scares from Ryan Neil jogged my memory of those earlier tales. Mr. Suzuki’s easy akadama / pumice combine has served me properly and these tales don’t heat me to lava.
Lava, aka scoria, generally utilized in bonsai media
Final yr I used to be in dialog with my former apprentice Andrew Robson who does a whole lot of touring and repots extra bonsai in varied soil media than I do, and he’s developed detrimental opinions about lava, notably purple. Listed below are Andrew’s observations:
As a bonsai skilled who travels to work with college students throughout North America and with a big assortment of my very own, I find yourself repotting a number of hundred bonsai every repotting season. One factor I’ve observed is the impact of various soils in numerous areas throughout North America, and with totally different talent units. Whereas the skilled bonsai neighborhood has come to the consensus that volcanic soils work greatest in a bonsai pot for optimum root progress, I’ve noticed that lava grows worse roots than pumice and akadama alone.
I don’t make the most of lava for a lot of causes, however the at first is the basis techniques I routinely see in it. Virtually with out exception, each bonsai I’ve repotted the place lava made up no less than 30% of the soil combine has had poor roots. Oftentimes after I take these bonsai out of the container, a lot of the soil simply falls away as a result of there isn’t the effective root mass to carry all of it collectively. In my expertise, and now the expertise of my college students and shoppers, lava isn’t creating the basis techniques that we’re on the lookout for. The identical actual bonsai, switched to an akadama and pumice combination, grows roots which can be far superior in a a lot shorter time period.
There’s just a few different causes I can’t stand working with lava. Apart from the poor root progress I see in it, it’s extraordinarily heavy in comparison with the choice (pumice). It could actually add a whole lot of weight to a bonsai pot, particularly a big bonsai. Lava can also be onerous and can destroy the sharp fringe of bonsai instruments with only a few repottings. Plus, it’s another materials to supply, buy, sift, and blend up for our bonsai. For all these causes, I keep away from lava with a ardour.
12 months after yr I proceed to see the identical factor as I repot bonsai throughout North America: poor roots, heavy timber, and boring instruments when lava is over-utilized within the soil combine. Lots of the high bonsai gardens in Japan go with out lava for a number of the most useful bonsai on the planet, and if these timber can thrive with out it ours undoubtedly can as properly.
If you happen to take your bonsai out of the pot after a few years and all of the soil falls away, otherwise you lower the circling roots and all of the soil falls away, it’s most likely not a soil combine that’s working.
I all the time encourage bonsai practitioners to maintain doing what’s working properly for them even when it’s not one thing I train or follow. However over the past a number of years I’ve moved away from utilizing lava in my very own and my scholar’s bonsai pots, and we couldn’t be happier with the outcomes.
—Andrew Robson
Andrew’s findings are documented on this video (sorry, could solely present on a desktop model):
Mr. Suzuki used 2/3 akadama, 1/3 pumice, which is prohibitive for a lot of Westerners. I take advantage of 1/3 akadama, 2/3 pumice for conifers, and 1 / 1 for deciduous. Most of this has been an financial resolution primarily based on the expense of akadama. I’m exploring 100% pumice as it’s low-cost the place I stay, and discover superb root progress, although the basis construction is totally different than in akadama. I’ll report in one other submit about that.
Lava, nevertheless, in 100% proportion typically creates anemic root constructions. The supply of lava might be implicated right here, some maybe problematic and others benign. Typically it creates good root constructions, different instances poor. In case your supply is working for you, use it. If not perhaps evaluate to pumice some yr.
Lava can work—some nurseries in Japan use it in excessive proportions, as much as 100%. In Indonesia it’s typically the key soil element. Right here in North America I’ve my doubts all sources are protected.
Please learn via the feedback, as many have raised factors which can be value exploring. I want to state clearly: when you’ve got a supply of lava that’s working for you, creating the effective, strong blocks of roots that Andrew’s video exhibits, then maintain utilizing it. This submit is supposed to lift a flag of warning that lava might not be as predicable as pumice, which is its different.
