PERSISTENCE OF SPOTTED KNAPWEED (CENTAUREA-MACULOSA) SEED IN SOIL

Experiments were established in 1982 to study the loss of viability of spotted knapweed seeds (achenes) in soil. Greater than 50 and 25% of buried seeds remained viable but dormant after 5 and 8 yr at two locations, respectively. Decline in seed viability was also measured in two natural seedbanks. Although the soil seed reserve decreased by 95% over a 7-yr period, approximately 400 000 viable seeds per ha remained, indicating that spotted knapweed seeds will last for many years in soil.