They are brown, four to eight mm long and flattened on one side. Life History Noogoora burr is a summer growing annual plant. Germination occurs between August and December but can occur at any time of year under favourable conditions. Ripe burrs begin to appear in June, continuing until the plants are killed by drought or cold. Ecology Noogoora burr is found in a range of soil types, but frequently prefers floodprone areas and is tolerant of waterlogging and saline soils.
Growth is best on deep fertile soils in disturbed or open sites.
Once the plant is mature enough to flower, at least some viable seeds can beproduced from plant reserves of water and nutrients. Closely spaced plants produce fewer burrs while widely spaced plants grow bigger and produce more. Hence partial control has little effect on the number of burrs produced. One of the two seeds in each burr germinates at the first rains while the other remains dormant until inhibitors have been dissolved out by water. This helps the plant survive poor seasons.