Seasonal Development of Established Johnsongrass

Abstract

Growth of tops and rhizomes of established johnsongrass(Sorghum halepense(L.) Pers.) stopped almost completely in the cool winter season. Rhizome growth started in spring later than topgrowth. Rhizomes constituted more than 90% of the total subterranean weight. In a sward of pure johnsongrass, 60%, 30%, and 10% of the total subterranean weight were found in the 0 to 15-cm, 15 to 30-cm, and 30 to 45-cm soil layer, respectively. Water-soluble sugar content in rhizomes was high in early winter and in early summer and low in early spring and in fall. Less water-soluble sugars were found in shallow than in deeper rhizomes. In winter the sugars accumulated mainly in the deepest rhizomes. No clear relation was detected between the sprouting percentage of rhizome buds and growth, sugar content, or seasonal climatic factors. No case of complete sprouting inhibition was recorded during the year.