The Winnow Wizard

Developed at Wild Garden Seed and now in use at seed companies across the United States and Canada, the Winnow Wizard is a game-changer for small-scale seed production.  In addition to replacing manual fan winnowing, the Winnow Wizard can perform precise density separations to remove hollow/immature seeds, difficult chaff/weed seeds, and heavier dirt/rocks.  It has saved thousands of labor hours and many thousands of dollars – both through time savings and through bringing unsaleable lots up to acceptable germination rates.


Inspired by the sterile laminar flow hoods in my microbiology background, the Winnow Wizard uses a pressure differential across a series of perforated metal grates to create a steady, even, adjustable flow of air.  By changing grates and varying blower speed, airflow can be adjusted from a gentle breeze for tiny yarrow and snapdragon seeds up to a strong wind for brassicas, corn, and beans.

In contrast to fanning mills, air separation occurs in a visually open area allowing for continuous monitoring and adjustment during operation and eliminating the potential for seed contamination between lots.  As a precision density separator, the Winnow Wizard performs many of the same functions as a gravity table at a fraction of the cost with no minimum lot size, no cleanout time, and simple, intuitive adjustments.

Following the model of the Open Source Seed Initiative, this is an open source design.  I do not intend to seek a patent, and publication of the plans online legally precludes any other entity from patenting it.


  • Wide adjustable range of wind speeds for seeds of all types.
  • Vibrating feed tray with adjustable angle and slot width for different seed shapes and sizes.
  • Hopper holds up to 12 gallons of seed, with sliding gate for slow-feed, accurate winnowing or fast-feed, rougher winnowing.
  • Hopper support (along with hopper and feed tray) easily removed for manual pouring of very small lots or non-flowing seeds.
  • Seed dividers rest on ruled rails; the optimal setting for each seed type can be dialed in and repeated.
  • Two dividers and narrow bin can split the seed stream into three fractions: good, mixed (for re-winnowing or further processing), and trash.
  • Hopper agitator allows dirty, dusty, or papery seed to feed automatically from the hopper.
  • Magnetic hopper gate (optional) uses powerful rare-earth magnets to deflect dirt and rock particles out of a falling stream of seed.  Works best with small seed, and efficacy may vary with magnetic properties of local soil.

Purchase a Wizard

After building 105 Winnow Wizards by hand in the Wild Garden Seed shop, I have handed off manufacturing to the skilled manufacturing team at Oppen Works in Viroqua, WI.  All Winnow Wizards now ship with a 1 HP blower for better separation of large seeds, although the airflow can still be adjusted to a gentle breeze for the smallest flower and herb seeds.

To place an order for a Winnow Wizard, please visit the Oppen Works website.  For questions regarding potential applications, functionality, and shipping, please email me.


Oppen Works (2023+) Winnow Wizard (1 HP) techniques and operating manual (PDF).

Winnow Wizard (3/4 HP, 2016-2022) techniques and operating manual (PDF)

Manual de operacion – Español (3/4 HP, 2016-2022) (PDF)

Winnow Wizard (1 HP, 2018-2022) techniques and operating manual (PDF)

Setup, operation, maintenance, and troubleshooting.  Detailed descriptions of winnowing techniques to remove chaff, hollow/immature seed, and material heavier than seed.  Probability-based techniques for winnowing flat seed.  Instructions for hopper agitator and magnetic dirt removal.

Seed cleaning strategies (PDF)

Overview of the seed cleaning process used at Wild Garden Seed, with complete process descriptions for kale and lettuce seed.  Discussion of the advantages and limitations of winnowing, and how best to combine winnowing and screening steps to clean seed efficiently.  Listing of useful screen sizes for common vegetable seeds.  Table of screens and Winnow Wizard settings across a wide range of seed sizes.  Summary of ways in which the Winnow Wizard has streamlined and improved seed cleaning at Wild Garden.