Growth, Survival, and Quality Components of ‘Sangmok’ Tea (Camellia sinensis (L.) O. Kuntze) Cultivated in Volcanic Ash and Non-Volcanic Ash Soils on Jeju Island, Korea

Tea (Camellia sinensis (L.) O. Kuntze) quality is shaped by soil, but comparisons among Jeju soil types are lacking. ‘Sangmok’ cuttings were grown for 33 months in three Jeju soils under identical greenhouse conditions—black volcanic ash soil (B-VAS), very dark-brown volcanic ash soil (VDB-VAS), and dark-brown non-volcanic ash soil (DB-NVAS)—and compared for survival, growth, and leaf amino acid and catechin profiles. Volcanic ash soils had more organic matter and nitrogen but less phosphorus and micronutrients than DB-NVAS. Survival (88.9%, 50.0%, and 55.6%; not statistically significant) and height increase (410.9%, 302.2%, and 116.1%) in B-VAS, VDB-VAS, and DB-NVAS were numerically greatest in B-VAS. The final DB-NVAS height-increase value reflects a single surviving plant and should be interpreted with caution. Total amino acids and theanine were 2.6- to 3.6-fold higher in volcanic ash soils than in DB-NVAS, whereas epigallocatechin (EGC) and epicatechin (EC) were higher in DB-NVAS, giving catechin quality index (CQI) values of 3.83, 3.13, and 2.20 and amino acid/catechin (A/C) ratios of 0.31, 0.28, and 0.10. In this pilot planting, survival was numerically highest in B-VAS, and the volcanic ash soils showed greater growth and higher amino acid levels in the pooled shoot samples, whereas the non-volcanic ash soil showed higher catechin accumulation despite weaker growth; these soil-type-level patterns are testable hypotheses for soil-type-informed ‘Sangmok’ cultivation that require confirmation in replicated trials.