Yes, you must always declare tulip bulbs when entering the United States or traveling between most non-EU/UK borders in 2026. Agricultural products are strictly regulated to prevent the spread of invasive pests and diseases like the "bulb mite" or fungal pathogens. If you are entering the U.S. from Europe, the bulbs must be dry, free of soil, and accompanied by an official Phytosanitary Certificate from the country of origin (e.g., the Netherlands). Even with a certificate, a Customs and Border Protection (CBP) officer may still inspect them. Within the EU and between the UK and EU, "plant passport" rules apply for commercial movements, but private travelers should still declare them to avoid heavy fines if they are found during a random bag check. Failing to declare can result in the immediate seizure and destruction of the bulbs, plus a civil penalty starting at $300. Always look for "Traveler-Certified" bulbs at major European airports, which are specifically packaged and certified for international transport to simplify the customs process.