Lettuce is the other seeed crop that took me years to learn how to clean well (radishes being the first).
The basics are like other dry seeded crops (thresh, screen and winnow ad nauseam) but to do a good job I’ve had to pay a lot of attention to the threshing and final screening.
(If you want to read more about growing lettuce for seed : growing lettuce seed under field tunnels and growing out crossed-up lettuce seed)
Harvesting Lettuce Seed
I keep a regular eye on the lettuce plants to catch them as they flower.
After flowering, the lettuce blooms close up.
A couple of weeks later, the flowers open again to reveal little fluffies at the end of mature seed (kind of like dandelions).
Since the seed doesn’t all mature at once, some folks walk their lettuce patch every couple days and shake the plants into bins or paper backets to collect the seed. I’ve tried this approach but don’t have the time to handle the plants this regularly.
Instead, when about 1/2 the flowers are mature, I harvest the whole plant.
I cut the plants above the roots (keeping dirt in the garden!), pile them in bins, and bring them back to the barn.
Drying Lettuce Seed Plants
I spread the lettuce plants out on tarps with a fan blowing air over them. I rotate the plants at least once a day so that the leaves dry down rather than rot.
If I have a little lots, I dry them upside down in a bucket.
The lettuce plants usually dry for 1-2 months before I process the seed. By this time the plants are completely dry and most of the seed has matured.
Threshing Lettuce Seed
Whereas we now stomp most seed crops to thresh them, we put on kid gloves to handle lettuce.
We rub the plants vigorously between our hands so the flowers fall apart dropping the seed and fluff.
This leaves the stems bare. I try not to break many stem pieces into the mix as they can be tough to later extract.
Screening Lettuce Seed (First Time)
I usually skip the 1/2″ screen and move right to the 1/4″ screen.
I separate the seed and chaff into the bin below and leave any stem on the screen. This is where cleaning lettuce seed gets tricky because the chaff is similar in weight to the seed and the fluff doesn’t seem to want to let go.
At this point I turn to more specialized equipment.
Screening Lettuce Seed (SeconD Time)
This is my favorite colander. The size of the holes are perfect for little oblong seeds (such as lettuce).
I rub the chaff-seed mix through.
This extracts the coarse material. I use this screen a few times and wind up with seed and a bit of fluff.
Winnowing Lettuce Seed
At this point I winnow delicately. If the seed is still dirty. I winnow again a bit more aggressively and perhaps run the seed through my colander another time.
One of the biggest tricks I’ve learned is to not try to save every last seed. When I accept losing a bit of seed, I can get the remaining seed much cleaner.
This is about as clean as I can get most lots with screens and fans. I pick out some of the remaining bits but have to live with the rest.
I apologize for the delay in getting this post up (Brian Creelman has been asking me to post about lettuce for nearly a year.)
Some of the delay is because I’m not much of a lettuce seed man – I’ve often had trouble getting lettuce seed crops to maturity and even though I’ve been cleaning lettuce seed 10 years, I still can’t get it as clean as most other seed. I’m currently looking into some seed screens from Hoffman Manufacturing. If these work out maybe I’ll become a lettuce seed cleaning maniac. I’ll keep you posted!
The rest of the delay is that I’ve been conference and workshop hopping this past month and any my spare time has been going into our new website. I’ll tell you guys more about all that soon …
