Germination Enhancement of Common Honeylocust (Gleditsia triacanthos) Seeds by Scarification

There are numerous superior cultivars commercially available that are propagated by bud grafting to a seedling rootstock. This requires adequate germination and seedling production by commercial producers. Common honeylocust (Gleditsia triacanthos L.) requires scarification to break physical dormancy of the seed. The influence of various scarification methods on the germination of the common honeylocust seeds was investigated. Seeds harvested from a female plant grown as a street tree in Fargo, ND, were chemically scarified for 0, 1, 2, 4, 6, 8, 10, 12, 14, 16, 18, and 20 hours in concentrated sulfuric acid and were geminated in peat-lite mix (Sunshine Mix #1) under intermittent mist. For comparison, two sets of seeds were also mechanically scarified or treated in boiling water. Seeds that were mechanically scarified or boiling water were germinated in the same root substrate under the same misting system. When scored for germination in 10 days under mist, germination of treated seeds was 0.3%, 98.0%, 98.0%, 99.9%, 88.0%, 80.0%, 33.0%, 8.05%, and 2.0%  at 0, 1, 2, 4, 6, 8, 10, 12, 14, 16 hours, respectively. Seeds treated with sulfuric acid for 18 hours or longer were killed. Seeds scarified mechanically showed 98.0% germination, while those treated in boiling water showed 18.0% germination. Result of this study indicates maximum seed germination can be achieved with a 1–4 hour treatment with concentrated sulfuric acid or mechanical scarification. Seed soaking in sulfuric more than 6 hours was undesirable. The possible use of diluted sulfuric acid during seed scarification was also tested for safety and practicality.