I have some yellow Crabapple seeds from a single crabapple tree that grows wild here, it's so huge and old but the wildlife go crazy for crabapples! I could send you a few seeds, it would be worth growing these into trees as they self pollinate but also pollinate Apple trees if a cultivar needs pollen to produce fruit. I sow them in pots outside in full sun keep soil moist but not soaking wet and they sprout by themselves once it's warm outside. I transplant them to individual pots once they are a few inches tall or just plant each seed in its own pot.
Even if you can't use them for trading because it takes few years for fruit in the long run a tree will provides hundreds of seeds each year once it gets fruit.
