PEER-REVIEWED ARTICLE bioresources.com Shakhes et al. (2010). “Kenaf for papermaking,” BioResources 5(2), 1268-1280. 1268 EVALUATION OF HARVESTING TIME EFFECTS AND CULTIVARS OF KENAF ON PAPERMAKING Jalal Shakhes, Mohamma Reza Dehghani-Firouzabadi, Pejman Rezayati-Charani,* and Farhad Zeinaly This study investigates effects of six kenaf cultivars named Cubano, Niger, Cubano 2032, 9277, 7551, and 7566 and three harvesting time stages on the properties of pulp and handsheet paper made from kenaf. Six cultivars of an Iranian kenaf (Hibiscus Cannabinus L.), were planted on 19 May 2007, and harvested after 85, 105, and 135 days. It was understood that with the increase of plant age, fiber yield increased. Maximum yield at each of three harvesting time stages was related to Niger. Consequently, if a high fiber yield is sought, Niger can be recommended, but for a paper with high strength properties, Cubano 2032 is strongly suggested. This cultivar produces a paper with significant burst, tear, breaking length and fold endurance even though its yield was somewhat lower than that of Niger at short harvesting times. Moreover, at second harvesting time stage, maximum strength properties of handsheets such as burst, tear, and breaking length, were seen in Cubano, though the fiber yield of this cultivar was a bit lower than Niger, but still more than Cubano 2032. We showed that a minor positive change in the handsheet properties could be achieved through harvesting kenaf at the third stage as compared to the first and second stages. Keywords: Cultivars of Kenaf; Harvesting time; Papermaking; Mechanical properties; Niger; Cubano Contact information: Department of Wood & Paper Science & Technology, Faculty of Forestry and Wood Technology, Gorgan University of Agricultural Sciences and Natural Resources, P.O. Box 49138-15739, Gorgan, Iran; *Corresponding author: P.rezayati@gmail.com. INTRODUCTION The use of non-wood plants for papermaking purposes has been a subject of debate for some time. Some nonwood plants are often proposed as effective solutions for the growing shortage of raw materials or even as substitutes intended to avoid tree felling. An increase in worldwide consumption of wood-based products and a decrease in forest resources have raised potential demands for supplemental nonwood fiber sources. Kenaf (Hibiscus cannabinus L.) is an annual plant with a high fiber yield. It is an herbaceous annual plant grown in many parts of the tropics and in some sub-tropical and warm temperate areas for its bark fibers used as a substitute for jute in cordage and sacking. The kenaf plant contains two distinct fiber components, bark and core. The bark (bast) fibers constitute 35–40%, and the core (woody) fibers compose 60–65% by weight of the stalk (Khristova et al. 2002; Touzinski et al. 1973; James and McCamley 1981; Kaldor et al. 1990). Therefore, the plant has been considered as an alternative fibrous crop to wood-based products, particularly in pulp and paper-making industries (Kaldor 1989; Kaldor et al. 1992; Ohtani et al. 1994; Pande and Roy 1996, 1998; Calamari et al.