Bittersweet does not require supplemental watering. However, even though it is pretty self-reliant, even during drought periods, regular watering does improve its overall health, and thus, its fruiting. While vines growing in naturalized areas of the property, in woods or along roadsides can be left to their own devices, water those that are being cultivated as ornamental features in a residential yard when other plants are being watered.
Sprinkle a handful of an all-purpose granular fertilizer on the soil around the vine stem each spring for the rain to soak in. This provides the nutrients that a bittersweet vine needs for the year. For more information see the file for Fertilizers
Consider Plant Growth Activators
There are on the market a growing number of products that will help your plants become healthier, more drought resistant, more disease resistant, and even more insect resistant. These products are generally easy to use and not terribly expensive. If you want to give your plants some oomph, check out New Technology In Plant Growth Activators
Spread a 2 or 3 inch layer of some organic material such as chopped leaves or wood chips on the soil around the bittersweet stem. This will help the soil retain moisture, keep down weeds and protect the woody stem from injury from lawn mowers. For more information see the file on Using Mulch
Prune bittersweet regularly every winter. Remove branches with berries for use in decorations such as wreaths and dried arrangements. Prune away broken, diseased or crowded branches to maintain plant health. Control the spread of these aggressive vines by judiciously trimming back rampant branches.
Taking cuttings from existing plants can reproduce bittersweet vines. This is a bit tricky. Snip off sections of young stem about 4 inches back from their tips. Place them in a plastic bag immediately so that they do not loose any essential moisture while being transported to the house. Remove the lower leaves from the stems, then dip the cut ends into a rooting hormone powder, available at garden centers. Stick them into a pot or shallow dish filled with moist sand or perlite. Keep them moist and they will begin to develop roots in a few weeks. Once a root system is developed, they can be transplanted to a pot with regular soil until it is time to go outdoors in the spring.