Influence of capitulum maturity on achene germination of Senecio jacobaea and Carduus nutans

Abstract

The influence of capitulum maturity on achene germination was investigated for Senecio jacobaea L. and Carduus nutans L. Germination of achenes from capitula in full flower was negligible for both species but as the floral tissues began to senesce the germination percentage rose to at least 50% for all populations investigated. S. jacobaea achenes with floral parts abscised or absent were generally more viable than achenes with floral parts attached, and seedlings from such achenes exhibited higher growth rates. C. nutans did not exhibit any consistent trends.

Keywords:

• achene
• capitulum
• germination
• nodding thistle
• Carduus nutans
• ragwort
• Senecio jacobaea