Seeds: Perennial Food Crops & Soil Builders

My name is Justin Hanseth. I live in Seattle, Washington, and implement permaculture design practices in a number of locations throughout the surrounding area. I am currently helping to design and construct a farm on the site of a new hospital being built in Burundi, Africa. My hope in writing to you is to obtain seeds that will grow in Burundi. From what I can tell, the site will be in a microclimate comparable to that of Houston. I have a friend living in Houston, who offered to collect and send/bring any seeds she can find to Seattle for me.
My primary interest is food plants (mainly perennials), but I would also be interested in medicinals, soil builders, or other multi-functional, perma-groovy crops. The only thing I would NOT want would be potential invasives. Do you have any excess seeds to share? Do you know of anyone else in the Houston area who does? I would love to hear any and all ideas you have about how my friend can best find seeds to bring me from Houston. Every seed I come by will be grown with utmost care and respect, and will contribute to feeding malnourished people in need of food.

Thank you for taking the time to read this.

Sincerely,

Justin Hanseth