Yellow rattle spring watch 2016
Spring in our open meadows, as marked by the germination of yellow rattle seed, was confirmed on Good Friday March 25th; almost three weeks later than usual.
Seeds that were either sown last autumn, or shaken from hay in summer, spent the winter lying on the wet soil surface exposed to winter weather. Rather than being an endurance test, as one might imagine, this is just the stimulus yellow rattle seeds require: 3 or 4 months of prolonged chilling release yellow rattle seeds from their enforced dormancy. In this primed condition the seeds are set to germinate at the first sign of spring.
As with bumblebee queens, frog-spawn and other indicators of spring the first appearance of yellow rattle varies from year to year: the first week of March is in our experience typical for eastern England.
Germination of yellow rattle in our open meadows this year was finally confirmed on Good Friday March 25th; almost three weeks later than usual.
The first part of winter 2015/16 was exceptionally mild right through into the new year. We began to wonder if there would be a long enough period of winter weather to break yellow rattle seed dormancy. We even questioned whether that yellow rattle might fail this year, and even if this was a sign of global warming and trends to come? Yellow rattle seed only needs chilling rather than freezing to trigger its germination; based on past years a cool to mild winter is still sufficient to synchronise yellow rattle germination in spring.
The delay in germination of yellow rattle we have observed in open meadows could be due to late arrival of a winter chill to break dormancy. Temperatures over the last few weeks have generally been below average so spring has got off to a rather slow start; it could this that has been holding back germination (we did first observe germination in more sheltered seed trays a week or more ago). Either way we are delighted it has finally made it through.
This synchronised early emergence of yellow rattle is critical: the seedlings must grow quickly to grab space before the surrounding spring flush of grass closes in and denies them light. If successful, the young plants will soon attach themselves, via their roots, to nearby grasses and other plants to extract nutrients from them. Yellow rattle will flower in early summer and complete its life cycle when its seeds ‘rattle' out to fall back to the ground in July.
Posted on 25 March 2016,