That is a great idea! I have two itoigawa from him and I am almost certain they are the same variety, but the mother plant is much less vibrant and I can’t figure out why. Do you keep yours in full sun? I’m starting to think that there is some sort of light issue, the other one I have that gets more aggressive sun has a lovely color.
Unfortunately extreme heat is a constant for most of the year but I’m lucky to be able to stay around my place most of the time. I’m starting to favor Japanese’s black pine because they seem to deal with it better. I actually just bought 3 more seedlings from John. That isn’t to say the junipers struggle, but they do stress a tiny bit. Funnily enough, I got at least one or two other people from the club to buy itoigawa mothers from him so there will probably be quite a few Eads itoigawa in Austin in the years to come.
Last year, the pacific northwest was a bit of a experimental laboratory for extreme heat and we hit some records that exceeded even what Texas gets. I do much of my growing on a large, south-facing deck. It is mostly unobstructed from sun in the summer and is up against a wall of light colored siding along with very large windows and sliding door glass that reflect light back on the deck, so things get
intense. With my cooking temperature sensor, I measured some insane temperatures on various surfaces, well in excess of ambient (which hit 116F / 46.6C a couple times).
In this environment, I found that most of my conifers thrived really well, but I was able to keep up with watering.
What I put in the roasting oven and did well: all except smallest junipers, JBP, scots pine, lodgepole pine, shore pine, korean pine
What I sheltered under an awning for the hottest parts of the day "just in case": JWP, western hemlock, lawson cypress (chamaecyparis lawsoniana), some smaller juniper material (cuttings of itoigawa, kishu, western juniper, etc).
What showed some heat damage within just a day or two: Subalpine fir
What showed some heat damage later: Bristlecone pine
What did badly overall and showed stress: White spruce. I'm starting to think I may have the wrong type of "nanoclimate" for this, even if one could grow it somewhere else in my neighborhood.
Interesting thing with all these species, they all surged with growth during this period of weeks, the junipers too. Note that all my junipers were in free-draining media.
Similar to your observation, I find that the trees that are in the corner of the deck with the most sun (i.e. extra couple hours of sun relative to the ones closest to the wall) by far have the most lovely color (as you say) and texture (for the pines in particular, a firm plasticky shiny texture).
It's my personal belief that free-draining media (in contrast to soggy retentive media) allows trees to draw water more effortlessly in order to cool themselves. It seems true that this comes with the cost of more frequent watering/monitoring, but that the ease with which trees can pull on that water makes it worth it. I've noticed that regardless of species, tree type, OR sun exposure levels, soggy retentive soils yield difficulty in self-cooling and stress in extreme heat. This is just anecdata/theories though. Driving around Oregon and looking at coniferous tree+shrub grow ops and also looking at tree farms similar to
@JEads operation, you see a lot of trees in full-day, full sun, even starting from fairly small material sometimes. IMO really what development-stage growers should be figuring out how to do is how to keep trees at optimal cooling rates so they can keep vigor high and actually take advantage of heat waves, at least prior to going into a bonsai pot when things get a bit more sensitive.
Also during last year's crazy multiple heat waves, I discovered that my cottonwoods (from yamadori to small cuttings) should be on the sunny deck with my conifers. IMO, Cottonwood is borderline immortal and laughs at stress. Try a populus species if you can water often!
