It's not mandatory, but it sure is helpful. Common and Latin names, germination and growing information, type of plant (annual, biennial, perennial), and the date of seed collection can all be very useful information for the receiver. In lieu of writing all this out on the packets, you could send an URL if you can find the necessary information online, but at minimum label each packet with the name of the seeds being sent and from whom.
If you are not absolutely certain of the exact identity of the seeds you are trading, tell the other trader so. Mistakes and disappointments can be kept to a minimum when such communications are made openly and honestly.
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