Seedling recruitment is episodic. Establishment and survival depend on adequate rainfall. Rainfall followed by hot weather is likely to result in the death of all seedlings and juveniles. In drier conditions, autumn has been the best season for growth and maturity; spring recruits have faced major mortality during the hot dry summers.
The best seedling recruitment episode we have noted was immediately after good rain in February 2003, which followed a very dry 2002, including a record period without rain. We particularly noted an abundance of short-lived ephemerals including Ranunculus sessiliflorus and Daucus glochidiatus. Whether it was the dry conditions in the soil or the record high temperatures reached that broke the dormancy mechanisms for many species, we do not know. The relatively open soil surface conditions in both previously burnt and unburnt areas may also have been factors in juvenile survival.
In recent years during a long period of below average rainfall, short periods of rainfall of as little as 30 mm have caused pulses of seedling germination but subsequent lack of follow-up rain has lead to death of all seedlings. For example in 2005 all seedlings of Pimelea spicata, Ranunculus lappaceus, Daucus glochidiatus and Rhodanthe anthemoides died. Similarly cohorts of *Sida rhombifolia seedlings germinating following fire, have died in dry conditions. Continuing conditions like this will deplete the soil seedbank. While this may be deleterious to native species it may reduce the number of individuals of some weed species.
Asterisk * indicates exotic species naturalised at the Australian Botanic Garden.