Bittersweet Hasn't Produced Blooms or Berries

We have several bittersweet vines that never produce blooms or berries. I added a male plant last year, but that didn't help. How can I get these vines to produce their signature red fruit?

Your new plant may not have flowered this first season. Thus no pollen to fertilize the females and produce fruit. Or you may have all male plants and in that case no females to produce the fruit. Watch for flowers next spring. Then get out a hand lens and check the flower parts. The male blossoms have pin-like structures called stamens while the females have a swollen vase-like structure in the center called a pistil. You may need to add a female plant or two if you currently have all male plants. Too much nitrogen can also interfere with flowering and fruiting. Avoid high nitrogen fertilizers and consider having your soil tested.