Abstract: In the suburb of Jinhua, the caloric values and ash contents of ten weed species were measured during their reproductive periods.These ten species include Veronica didyma, Polygonum hydropiper, Plantago asiatica, Plantago virginica, Ranunculus japonicus, Phytolacca acinosa, Roegneria kamoji, Poa annua, Lepidium virginicum and Torilis japonica.The main results are as follows: The average gross caloric values of the spikes, leaves, stems and roots of the ten weed species were(15.942), (14.293), (13.344) and(13.463 kJ/g) respectively, their average ash-free caloric values are(16.983), (16.219), (14.480) and(15.233 kJ/g), showing the order as spike leaf root stem according their caloric values.The average ash contents of the spikes, leaves, stems and roots of these ten weeds were(6.127%), (11.899%), (8.071%) and(11.383%) respectively, revealing that the leaves and roots had higher ash contents than their spikes and stems.The vegetative caloric values of Plantago virginica declined with the growth period, and their productive caloric values became higher with the increase of their population density.Analyses indicated that the weed species having lower caloric values might be a good choice to their adaptation to the undesirable environments, with obvious positive evolutionary significances.

Key words: weed, caloric value, ash contents