Timing of emergence.

Protocol

Seeds of three established populations (one in Italy, one from the UK and one from Sweden) of two weed species (Chenopodium album and Stellaria media) were distributed to a number of locations (UK, Italy, Germany, Sweden, Denmark and USA) for burial in identical substrates and weekly recording of emergence. 

In November 1999, 500 seeds of S. media and 500 seeds of C. album from a single source were buried at a standard depth in a pot. Separate pots were used for each of the three main seed sources (UK, Italy and Sweden). Identical pots, depth of burial, method of burial and compression and substrate were used across all the participating sites. 

Four replicates were used for each main seeds source (12 pots in total) and where available, a fourth additional local source of the two weed species were also included (16 pots in total). In November 2000, The numbers of seeds in each pot were increased to 1000 for each species (except the Swedish populations of S. media and C. album, where only 500 and 800 respectively were used because of low availability). 

Excel spreadsheets and template graphs were distributed to all participants to enable the data to be collected in the same format and no major problems in the setting up of this experiment were reported by any of the participating sites. 

Daily weather data was collected at each of the 8 sites throughout the study