TJ, in my experience………….
Your plan for your orchard layout is fine. I would not complicate it with diamonds, etc. 8x15, will work, but design it to match your mowing equipment. I’m on 8x18 which works for me. Sometimes I wish I had a bit more room within rows—perhaps 9’.
Your biggest battle will be with grass and weeds within the rows. They are probably the worst enemy of young trees. I’m not sure vetch is the answer. I use wood chips in each row of trees, but even with the chips, weeds and grass are hard to keep out. I use glyphosate, which is labeled for pawpaws. It’s used extensively by Kentucky State U, but be sure to clip all suckers down before applying.
I don’t like using tree tubes on grafted trees. Grafts need attention, and the tubes just interfere. The trees don’t need shading once they are about 18” tall—usually after one good full season of growth. If you are worried about deer, I recommend an electrified 3-D fence (plenty of references on line). Deer may not browse heavily, but they will quickly destroy a pawpaw tree with rubbing. Rabbits are generally only a problem for the very small trees. Keeping weeds and grass low will discourage rabbits (another strike against vetch). Establishing perches for raptors is also effective. For fencing around individual trees—if you must—see Northern Pecans blog for ideas.
Manure can be useful for nutes, but can be difficult to meter accurately. I use KSU’s recommendations on N fertilizer spread under trees before bud break. I generally use ammonium sulfate to keep the pH low.
Pawpaws are easy to graft, beginning when they are pencil caliper—in ground or container. I’ve had good luck planting out small trees and grafting them the same season. With good first-season growth, you should be able to graft in the second year. Availability of scionwood will probably govern your grafting timing. Grafts will grow well in containers, especially if you can control the temperature and moisture via a tunnel or even some kind of lean-to. 80 degrees is ideal. Don’t worry if you can’t graft your orchard trees until they have some size—the grafts will explode in growth from a tree with a good root system. However, I don’t like to graft a tree more than 1.5” in diameter, as it creates a weak area over time.
I am still trying to learn the best way to prune and shape a pawpaw tree. They are not like apples, which can be trained to create good crotch angles. Pawpaws naturally have a very poor crotch structure which is difficult to correct (think callery pear). Loaded with fruit, add in some wind—disaster in the making. KSU recommends a single leader, but in my experience that still does not prevent bad angles.
Good luck and keep us posted.
