Seed germination and seedling survival of invasive callery pear (Pyrus calleryana Decne.) 11 years after fruit collection.
The ability of seeds to persist long term and still germinate readily with substantial seedling survival are characteristics shared by many invasive plants, often leading to dominance of species in invaded sites. One rapidly spreading species in the United States is the Callery pear (Pyrus calleryana), which can form dense monocultures following bird dispersal of seed formed by cross-pollination among genetically different ornamental cultivars and rootstock. However, the length of viability of these seeds or their subsequent ability to germinate and survive as seedlings was unknown. We compared the percentage of seed germination and seedling survival using fruits collected from three cultivars in 2006 with a subsample kept in cold storage for 11 years; we also measured the viability of stored seeds that failed to germinate. Although seed germination declined, it continued to be substantial even after 11 years (45%-87%); seeds that did not germinate were viable in some cases, although this varied by maternal cultivar. Of those 11-year-old seeds that germinated, survival of the seedlings over four months was lower but still substantial (54-81%), compared to survival of seedlings generated from fresh seeds (91-95%). These results indicate that a prominent seed bank may exist in invaded sites, posing a challenge to management programs of the Callery Pear.