Chondrilla juncea in Australia. 3. Seed maturity and other factors affecting germination and establishment

Abstract

The relationship between seed colour and viability and also the effect of seed age, moisture stress, depth of seed burial, and soil type on the germination of skeleton weed (Chondrilla juncea L.) were studied at Wagga Wagga, New South Wales. As the developing seeds matured their colour changed from greenish-white through yellow to yellow-brown or olive-green. Some 25 per cent of the yellow seeds were capable of germination but then only for a short period after shedding. Fully coloured, mature seeds showed 80 to 90 per cent germination capacity and remained viable for two to three years when stored in open containers. A few samples were dormant for about 12 weeks but the majority germinated rapidly when ample moisture was available. Germination was delayed and decreased with increasing water stress. Soil type had no apparent effect on germination but emergence was inversely related to depth of planting. There was no emergence from below 13 mm (1/2 inch) in heavy clays or 38 mm (19 inches) in other soils. Surface sown seeds did not establish readily on compacted surfaces, emphasizing the importance of the cultivated fallow in increasing the rate of spread.