Pumpkins are usually grown using wide row spacing, and in Minnesota, the canopy does not close until mid-summer and the canopy senesces in early- to mid-autumn. This provides opportunity for establishing frost-tolerant or winter-hardy cover crops between rows before the canopy closes, which will continue to grow after pumpkin foliage is gone. To understand more about competition between interseeded cover crops and pumpkins, four species of clover (berseem, crimson, Persian, and red) were sown between pumpkin rows (10-ft spacing) in late June, and pumpkin yield and clover growth and N content were measured in the fall. Both ‘Cotton Candy’ and ‘Kratos’ pumpkins were studied. ‘Kratos’ yield (68.4 Mg / ha; 1185 fruit / ha), fruit size (9.7 kg), and fruit size variability (28%) were 1.8 times, 0.55 times, 3.2 times, and 1.1 times as much as ‘Cotton Candy’, but none of these responses were impacted by clover. Above-ground biomass of berseem, Persian, and red clovers averaged 0.41 Mg / ha in late fall (16 kg N / ha), but crimson clover yielded 1.2 Mg / ha (33.3 kg N / ha). Clover grown with ‘Kratos’ yielded 69% of the dry matter and 73% of the aboveground nitrogen (per ha) compared to clover grown with ‘Cotton Candy’. The average C:N ratio of all treatments was 18.3. These results show that clover interseeded into pumpkins, especially crimson clover, can grow successfully without impact on pumpkins. High-vigor pumpkins can reduce clover yield, however.
