Anyone have experience with 'Glenn Form' RAINBOW PILLAR serviceberry? Does it produce a good amount of fruit? I read online in a couple of places that only about 10 percent of its flowers produce berries compared to 30-40 percent average for other serviceberries. But I've only seen it mentioned in a couple places so don't know how true it is. It's a narrow one so fits my space really well but I want a good amount of berries for the birds! Thanks!