No-mow amenity grassland case study: phenology of floral abundance and nectar resource.
1. Popular campaigns such as No Mow May seek to encourage early-season forage resource for pollinators in urban green spaces. Land managers need to balance ecological benefits with extent of accessible amenity grassland. 2. To pilot the identification of a 'tipping point' when the nectar resource of unmown grassland exceeds that mown, we surveyed floral abundance in 30 plots on an amenity grassland site at 11 time points between late April and July. Each species' floral abundance per 1m2 was multiplied by published nectar sugar values to obtain an overall nectar sugar value per plot. 3. The nectar sugar value of no-mow plots was overall significantly higher than for mown plots. However, week-by-week analysis revealed that the first significant difference did not occur until mid-late May when no-mow plots yielded three times the nectar sugar value of the mown plots. In early-mid June, there was a significant eightfold divergence followed by a late June to early July decline. Common Ragwort (Senecio jacobaea) provided the greatest nectar sugar value, driving significant differences again in mid-July. No-mow plots contained twice as many (22 vs. 11) open flower broadleaf species compared to the mown plots. 4. Land managers could consider extending No Mow May management into June and beyond to maximize nectar sugar resource for pollinators. To comply with S. jacobaea legislation, a management plan and financial resource should be allocated to no-mow projects.