| Summary: | Spider plant (<i>Cleome gynandra</i> L.) is an emerging noxious weed, affecting cultivated vegetables in Queensland, Australia. It is a prolific seed producer, forming large seedbanks with variable seedling emergence. A study was carried out to investigate the seed biology of spider plant, focusing on its seed germination ecology, viz., influence of temperatures, illumination conditions, medium salinity, pH, substrate moisture, burial depth, and after-ripening. Freshly harvested seeds were negatively photoblastic and had combinational dormancy. Improved germination was obtained by physical scarification followed by soaking for 16 h, by dry storage for over 6 months, and by the imbibition of gibberellic acid. Maximum germination percentages of 70 to 80% were recorded under constant darkness at alternating day/night temperatures of 20/30 °C, or with 18 to 27 °C constant temperatures. Spider plant showed a broad tolerance to pH but only moderate salt and moisture stress tolerance, since only 42 and 26% germination were observed with 60 mM NaCl and at −0.40 MPa, respectively. Seeds placed on the soil surface did not germinate, however, at a burial depth of 1.0 to 1.5 cm, which resulted in <i>ca.</i> 80% seedling emergence. These findings will assist land managers to predict seasonal emergence and will aid in deploying management approaches to control this weed.
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