Much of this polarization may be attributed to lack of historical understanding, as detailed below by @Baisao:
viewtopic.php?p=37780#p37780
Florent gives a nice and sober description from a technical standpoint:
https://japaneseteasommelier.wordpress. ... megashima/
Let us first recall what the term “zairai-shu” or “mishō-zairai-shu” means in Japanese. This is what can be called an indigenous variety (or native variety). In short, this type of tea tree is opposed to cultivars (or varietal). A cultivar is obtained by selection (and, most often, crossbreeding), then multiplied by cuttings. In short, all the tea plants of the same cultivar are genetically identical. Conversely, a plantation of native varieties “zairai” is obtained by seeds, “zairai” tea trees are all genetically different. They do not have the same characteristics, neither aromatics nor resistance to diseases and climatic conditions. Moreover, they do not sprout according to the same timing. They give a non-homogeneous harvest, with leaves still very small and others already too hard, which makes it difficult to roll and dry, and whose aromas will not be stable.
Tillerman has a more critical perspective, though more from the taiwanese perspective, and maybe more about oolong:With zairai’s raw tea (aracha : unsorted tea, without final roasting), finishing is also an important problem: there is a lack of uniformity and contains a lot of very large leaves (atama) that cannot be integrated into the finished tea. The sort causes a huge loss (more than 20%, against less than 10 for a quality sencha with a cultivar), and the choice is how and to what extent we cut the large leaves to integrate into the final tea.
https://tillermantea.net/2017/04/seed-vs-cuttings/
Briefly, the main issues or challenges for zairai today seem to be:
- Multi-level heterogeneity from highly variable genetics, unsynchronized leaf growth, and difficulties of the sorting machines to evenly sort the non-uniform material
- Lack of clonal selection efforts to optimize taste
- Lack of market in Japan where optimal homogeneity with narrow sensory profiles are prized. This reduces incentive for farmers to even try to make good tea from the materials - resulting in poor processing and maybe suboptimal harvest times
- Too much magical marketing attracting mystical tea cult types
viewtopic.php?p=19966#p19966
Now what do the zairai aficionados say?
- Zairai can have less bitterness and astringency if from a pre assamica hybridization cultivar. Therefore they can be pushed with boiling water to extract the whole polyphenol profile.
- Some complain zairai lacks any immediate and obvious taste that has been selected for..in particular umami. This can be a good thing for people who find umami to be distracting or...filthy - considering umami scales with fertilizer use.
- Zairai can have stronger aromatics and mineral after taste. This is controversial, and is what Hojo likes to argue. He claims this can be attributed to the deep taproot of the seed grown bush. Many people disagree.
https://hojotea.com/en/posts-233/
Personally, I find the quality of zairai can be quite variable - and maybe more dependent on the curating abilities and taste of the vendor.
For example, the one offered by o-cha last year was very flat brewed in cooler water, and very astringent and bitter when brewed in hotter water. In contrast, the zairai offered by hojo is consistently floral and herbal - beautiful to some, but maybe lacking for umami obsessives. The key is to try from several different vendors. I list some in the next post.