Lignocellulose materials can be readily produced under tropical and subtropical conditions and converted to a variety of fuels through bioconversion methods. However, biomass production and plant quality may differ between plant species and morphological components of plants. The objectives of these two experiments were to: (1) determine the influence of plant height at harvest on Erianthus arundinaceum (Retz) Jesw-IK76-110 dry biomass (DB) yield; and (2) monitor changes in tiller density, quantity and quality of plant components with increased plant height. Experiment (1) determined the influence of plant height when harvested at 1.2, 2.5 and 3.7 m, mature stage in October (4.9 m), mature stage in December (4.9 m, plus inflorescence), and an additional treatment harvested in October, which received half the total N (168 kg ha(-1)) annually on DB yield from 1987 to 1990. Experiment (2) treatments were to monitor changes in quantity and crude protein (CP) and in vitro organic matter digestion (IVOMD, estimate of soluble cell solids) of green leaf, dead leaf and stem plant components, leaf area index and tiller number at 0.6 m plant height increments to a final height of 4.3 m during 1987 and 1988. Treatments from both experiments of the study received 25 kg P and 93 kg K ha(-1) in one application and 336 kg N ha(-1) y(-1) in single or split applications applied annually prior to regrowth of each harvest. Plants repeatedly harvested at the 1.2 m height and mature stage in December (Experiment (1)) produced a 4-y average yield of 5.2 and 51.5 Mg ha(-1) y(-1) DB, respectively. These same two treatments had a yield reduction of 100% (plants died) and 1% between years 1 and 4. Leaf area index increased quadratically to a maximum of 17 at the 3.1 m plant height treatment. Percentage green leaf, total tillers and live tillers decreased quadratically, while dead leaf and dead tillers increased linearly and stem increased quadratically as plant height was delayed from 0.6 to 4.3 m. Crude protein and IVOMD of green leaf and stem decreased quadratically with plant maturity. Knowing the quantity and quality of plant components at various physiological stages can be important to biomass producers, who need to make logical field decisions regarding biomass feedstock that should be utilized immediately after a freeze or stockpiled for later use.