Our first indication of the strong influence of annual precipitation levels on Cynara cardunculus reproductive traits. Numbers of heads per C. cardunculus plant, apparently viable seeds per plant, and seeds produced/m² for the first three years of a five year study, with results of ANOVA in sparsely (<30% cover) and heavily (> 50% cover) invaded sites. n = 12 random individuals per site. Tukey’s post hoc test indicates significantly different means. Rainfall (inches): 1997-98 (29.1), 1998-99 (7.87), 1999-00 (11.02).

Site 1998 1999 2000 p
Heads per plant
Heavy 4.8 ± 0.7ª 2.9 ± 0.3b 2.3 ± 0.4b 0.005
Sparse 3.8 ± 0.4ª 3.4 ± 0.4ª 3.6 ± 0.4ª 0.814
Seeds per plant
Heavy 798.3 ± 171.8ª 304.1 ± 82.9b 176.6 ± 59.3b 0.001
Sparse 643.4 ± 95.8ª 179.4 ± 82.1b 556.7 ± 959.3ª 0.002
Seeds per m²
Heavy 1337.21 ± 227.7ª 439.1 ± 55.3b 138.3 ± 7.0b 0.005
Sparse 117.96 ± 18.6ª 13.4 ± 1.5b 102.07 ± 22.0ª 0.004