Coming in to MSP from AMS today, I declared "yes" to "seeds, nuts, etc." (and also "more than the free allowance"). I told the agent I had tulip bulbs, bought at the airport. He looked at the box and scribbled on the receipt. He thanked me, mentioning that a lot of Global Entry people don't bother declaring them. That was it; maybe 30 seconds (most of which was finding the bag that had the tulips).