jim
i have no idea im guessing spring/summer due to you want the plant in the prime growing time. when you graft you wrap the graft and keep it humid with a bag or some individuals that do SMALL quantity are making little individual greenhouses for each with plastic soda or water bottles. in 30-60 days the are checked and see if the grafted piece has started to grow they assume the graft is taking and then its time to start to open up and let the new plant to thrive that is why i think fall and winter is bad UNLESS you are using heaters and grow lights to fake the plant its in the growth stage.
I AM NOT AN EXPERT AND HAVE NEVER GRAFTED I am is just using the research i have done and my knowledge about plants
