Seasonal Festivals & Plant Sales Friends of the National Arboretum I have two patches of perpetual spinach. Great crop, then all of a sudden one patch was covered in some sort of blackfly type of thing. I left well alone when I Embryo culture is a fascinating area of plant tissue culture that focuses on growing embryos outside the parent plant. Let's delve into the two primary methods: Mature Embryo Culture: What Zinnia elegans Benary's Giant Benary