I’ve heard Ryan Neil and others recommend that if you’re going to use collected moss, it needs to be local so that it is adapted to your climate and will survive. Otherwise, use sphagnum etc.
If I decide to collect this moss featured below (from my street), is there anything I need to do to it to prep it before application? Is it still better to just grow your own (for better aerobic purposes)?
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Is this “quality” moss? I have only one potted tree thus far in akadama, pumice, LR, and have considered applying it:
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Potted this last week to stay this size at is matures. Is it best to grow moss given my circumstances? Why or why not?
FWIW, don't get hung up on moss. At best it's a hassle and at worst it's a useless pain in the ass. Moss is a TEMPORARY thing in a bonsai pot. It's not worth actively cultivating for the most part, IMO, since caring for it takes away from caring for the tree underneath it (the care for both isn't the same and one can be detrimental to the other) Even if you get it established on the soil surface, it will wax and wane with the seasons, available moisture, fertilizer, even water hardness, going from green to brown and crispy. It does nothing for the tree, really, despite what many will say.
At it's worst, it can block or re-route drainage if it dries out and becomes impervious to overhead watering, it can die off all at once (from strong fertilizer application, a repositing of the pot into more direct and strong sun) rot and clog soil. It attracts birds constantly who dig up soil underneath as they flip off moss sheets looking for grubs and worms.
Even what you find locally IS NOT what will grow in your pot, as the location on the ground/sidewalk, parking lot, whatever, is not the surface of the soil in your bonsai pot. Such collected moss has a better chance at survival than the rip-off packets of "kyoto moss" sold at bonsai rip off stores, but it's still not foolproof. The best moss to grow in your pot is moss that establishes itself. It can eventually. Takes some patience and knowledge of how to set up the soil to allow it and not kill your tree.
Also, FWIW, moss is used in Japan mostly for exhibition preparation. It's arranged a few months before a show on bare soil. It takes some skill to make it look natural. After the show, it is stripped off and not replaced. It's seen as an accent plant.