Factors affecting seed germination of cadillo (Urena lobata).
Cadillo is an invasive species commonly found in pastures, rangelands, and disturbed areas. It is becoming a significant problem weed in Florida pastures and natural areas. The objectives of this research were to determine effective techniques to break seed dormancy and the effect of light, temperature, pH, water stress, and depth of seed burial on Cadillo germination. Cadillo seeds had significant levels of innate dormancy imposed by a hard seed coat; chemical scarification was the most effective technique for removing dormancy. Seeds germinated from 15 to 40 C, with an optimal temperature of 28 C. Germination was unaffected by pH levels. Water stress below -0.2 MPa reduced seed germination. Cadillo germination was not light-dependent and seeds emerged from depths up to 9 cm, with the greatest occurring emergence near the soil surface. Considering that Cadillo seed can germinate under a wide range of environmental conditions, it is not surprising that it has become a serious invasive weed in Florida.