Abstract
Horsenettle (Sonalum carolinense L.), a clonal perennial is native of the southern US, has been increasing as a serious weed in Japan. Control of the horsenettle is difficult because of clonal reproduction by its extensive root system. Therefore, whole structure of the root system, shoot emergence and its control mechanism within a clone, allocation pattern and strategy of vegetative reproduction were investigated. 1. The root system is composed of horizontal and vertical roots that are clearly divided. 2. Shoot emergence period is limited during one and half months of the spring because of its intensive intra-clonal control. 3. The shoots spread slower than the root system in a clone. 4. The root system has priority over other organs in dry matter allocation. 5. Dry matter allocation to the inside of a clone is higher than the outside in the shoots but not in the root system. Consequently, strategy of vegetative reproduction of horsenettle is conservative and tolerant to disturbance and stress. Therefore, eradication of horsenettle is not the purpose but the result of long and adequate control.
