<p>Knowledge on sapwood area estimation using allometric models and the anatomical features of wood and vessels is fundamentally essential for understanding crop water use. However, limited research has been conducted on the allometric models and characteristics of sapwood and vessels for most agricultural crops in Thailand. This research aimed to observe the relationship between sapwood area and branch diameter and that between sapwood area and branch circumference by a power function for nine selected tropical crops including coffee (<i>Coffea arabica</i> L.), mango (<i>Mangifera indica</i> L.), pomelo (<i>Citrus maxima</i> (Burm.) Merr.), cacao (<i>Theobroma cacao</i> L.), longan (<i>Dimocarpus longan</i> Lour.), durian (<i>Durio zibethinus</i> Murr.), longkong (<i>Lansium domesticum</i> Corr.), rambutan (<i>Nephelium lappaceum</i> L.), and mangosteen (<i>Garcinia mangostana</i> L.). Additionally, wood porosity and various vessel element characteristics were analyzed for these species. This research is the first to report novel findings that branch diameter (<i>R</i>² = 0.81–0.99) or branch circumference (<i>R</i>² = 0.96–0.99) could serve as predictor of branch sapwood area in these tropical crops based on a power function equation. Wood porosity of all studied crops was classified as diffuse-porous. Across all species, vessels were tube-shaped with tails, had simple perforation plates, and exhibited alternate intervessel pit arrangements. Variations in vessel grouping, length, width, and density were observed among species. These findings provide foundational knowledge for further understanding of crop water use, offering valuable insights to optimize water management for improved productivity.</p>