Seed hulls clinging to cotyledons are common in sunflower, radish, brassicas and many other microgreens. They are usually more of a quality and appearance problem than a growing failure, but heavy hull retention can make harvest and washing more tedious.
Why hulls stay attached
The hull normally softens during germination and falls away as leaves expand. Dry germination conditions, uneven moisture or a seed coat that was not fully hydrated can make it cling longer.
Keep germination evenly moist
Consistent moisture helps soften seed coats. This is one reason large seeds are often soaked before sowing and why covered germination works well for many crops.
Let leaf expansion do part of the work
Moving a healthy crop into light and allowing cotyledons to open often sheds many hulls naturally. Do not rush to pick every hull by hand the moment the tray emerges.
Use gentle brushing only when the crop can handle it
Once seedlings are sturdy, a very gentle pass of your hand over the canopy can loosen dry hulls. Delicate crops should be handled carefully because removing a hull is not worth damaging the growing tip.
Avoid soaking the canopy late in the grow just to remove hulls
Wet leaves at the wrong time can increase postharvest moisture and disease pressure. Focus on good germination technique first; remove remaining loose hulls during clean harvest and sorting.
Related: Should You Soak Microgreen Seeds? and Harvest and Storage Guide.
Sources: University of Maryland Extension; Penn State Extension; crop-production practice.
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