Flowering of contrasting white clover varieties in relation to daylength in controlled environments and in the field

The effect of 12 , 14 and 16 h photoperiods, given consecutively, on flower production in 10 varieties of white clover (Trifolium repens) in controlled environments, is described. The effect of natural daylengths from September to July on the same plants in the field was also studied in the following year. Relationships between morphological and physiological traits and flowering were examined. In controlled environments most plants flowered under the longest days, three times as many in the 16 h daylength as in the 12 h. Larger leaved types had a higher proportion of reproductive plants than did smaller leaved types. Floral initiation was not observed in the field until daylengths were in excess of 15 h. Increasing daylength increased flower production, floret and ovule numbers but did not appear to increase nectar production significantly.