Separating Seed from Plant for Restoration Seeding Effort

Hi all, the Delaware Center for the Inland Bays recently tried placing some hand harvested seed heads of widgeon grass into an oyster setting tank to let the seeds settle out from the plant material. The dream was we’d be left with pure seed and a little residual plant material after a few weeks. What we instead got, after several weeks in the setting tank (with two pumps and a bubbler running 24/7, and stirring the tank once ever three days) was a black muck layer several inches thick with seeds presumably buried inside.

I would classify it as a failure. One of the main issues was that the tank (and where it draws water from) is located in an upper river area that experiences huge blooms of mahogany tide and so the tank was effectively a kiddie pool for an algae bloom, plus all the decomposition that we were hoping would occur from the widgeon grass.

Next year we plan on using a tank in another area, presumably alleviating the issues with algal blooms and low DO. BUT, my questions are, does anyone have experience with this method of seed separation, any tips and tricks? Did we not leave the material in the tank long enough? Will it ever result in pure seed with a little plant material? Or does it always end in muck and seed mixtures? Just hoping for some discussion on what works for folks or if this is a waste of time and we should go back to direct planting after hand harvest. Thanks!

Hi there - I had this same experience with harvesting Zostera marina seeds in flow-through tanks. Separating seeds from detritus muck and algae was a nightmare. It was improved by reducing light to the tanks (reducing algae growth some), stirring tanks daily, and removing all unnecessary leaf/stem/etc plant components. It’s possible that using some sort of mesh at the bottom of the tanks would allow the seeds to fall through but keep detritus and algae above the mesh - but we didn’t try.

Randall Hughes at Northeastern University and Tay Evans at MA DMF both have experience with seed harvest and may have more to offer if you want to reach out to them!