The Korean Evodia, evodia danielli, or any of the other 5 or 6 sub-species of bee bee trees are great pollen and nectar sources blooming in late July when nothing else seems to be available. That is, at least here in the Atlantic “coastal, broadleaf forest, tulip polar region”.
So raising bee bee trees is a great thing to do. In fact, planting evodia is the one thing that every beekeeper should do! I know the tree is on the Pennsylvania state list of watch species for possible invasiveness, but I have observe it for the last 10 years and can see that while I does have the potential to spread due to the heavy seed set, the tree can be killed easily by cutting it down. This is very unlike true invasive species like multiflora rose or others.
Try to get your hands on the evodia hupehensus if possible, as the trees get bigger than e. danielli but all of them are good. E. hupehensus is available from Forest Farm on the West Coast.
If you got seeds this year and wintered them outside, or put them in sand and water in your freezer, some of them should be nearly ready to sprout in mid to late April. If you are able to break the seed dormancy thru this process of cold stratification, then you are on your way. Some of the little black seeds should germinate after a few days at 68-71 degrees Fahrenheit.
You should be careful however to protect the seeds, even in their planters and soil, as birds and squirrels love to dig for seeds and once they find yours, they all will be gone in short order! Placing a wire mesh or hardware cloth over the seeds is a good idea, until they sprout. Reportedly there are two other ways to break dormancy on the seeds, 1) by bring the seeds to a boil in water, and letting them soak overnight, and 2)rubbing the seeds gently between two sheets of sand paper, then doing cold stratification.
Then when they do sprout, be careful to protect them from slugs, as the slugs could find the delicious new leaves and devour them! I speak from experience. So, you can easily bait for slugs (away from your seedlings) using a saucer of beer left out overnight. They crawl in and drown!
In five or so years you should have a tree that is ready to bloom for the first time (at about 12 – 15 ft in height). If you want to make sure you have viable seeds to share in the future, make sure you have 3 or more trees, as they are a strange combination of both male and male-female.
This citation from Wikopedia is concerning plant reproductive biology: “A “unisexual” flower is one in which either the stamens or the carpels are missing, vestigial or otherwise non-functional. Each flower is either “staminate” (having only functional stamens) and thus “male”, or “carpellate” (having only functional carpels) and thus “female”.
If separate staminate and carpellate flowers are always found on the same plant, the species is called “monoecious”. If separate staminate and carpellate flowers are found on different plants, the species is called “dioecious”. Bee bee trees or evodia are both monoecious and dioecious but the pollen from the monoecious plant may not be available most years at the right time.
That is why you need both kinds of trees for seeds.
For more information on the sex of bee bee trees see the excellent article by Ayers in the 2007 American Bee Journal.