Getting to know American bittersweet
American bittersweet is one of the most ornamental of our hardy northern vines. This deciduous, climbing woody vine is native to our zone 3 area and is found growing in thickets, in stands of young trees, and along fence rows and streams. It grows vigorously and can kill shrubs or small trees on which it becomes attached merely by tightly girdling stems and branches.
Bittersweet makes no appreciable floral display; however, the fruit can be exceptionally beautiful. The clusters of yellowish-orange capsules separate, exposing bright, red-orange berries about September. These remain attractive through most of the winter. Cut and brought indoors, they make excellent long-lasting decorations. The leaves, bark and fruit are considered toxic and should be kept out of the reach of young children and pets.
Bittersweet vines grow well in most soils, in full sun or in shade. Adequate sun, however, is important for fruit production. The only attention bittersweet generally needs is a little pruning to keep the plants tidy or to limit their size. Pruning should be done in late winter or early spring. This is when branches are most visible.
Bittersweet is a dioecious vine, which means it has male flowers on one plant and female flowers on another. The two types of vines must be near each other to produce fruit. In May or June, small greenish-white flowers open in clusters at the ends of branches. Bees are the main pollinators, although wind may also act as a pollinator. One male vine can serve as a pollinator for six or eight female vines. It is the female vines which bear the attractive fruit.
Plants can be bought from a nursery in spring or propagated from seeds or cuttings. To start from seeds, collect the ripe fruit as soon as the capsules have split to reveal the crimson berries, sometime between mid-September and November. Spread the collected fruits in shallow layers and allow to dry at room temperature for 2 to 3 weeks. Then remove seeds from the capsules and allow to dry for another week. Seeds to be sown in spring must first be placed in moist sand or peat in a bag or container and kept in the refrigerator (34 to 41 degrees) for 3 months. This breaks dormancy and promotes seed germination. Seedlings will average about 50 percent each, males and females, But you can not tell which until they are old enough to bloom.
The best way to get the sex ratio you want is through vegetative propagation of plants from cuttings of known sex. Softwood cuttings can be taken from terminal (tip) shoots that are soft and immature with two or more nodes (the point on the stem where a leaf is attached). The 3 to 5 inch cuttings with leaves attached should be taken in midsummer and cut squarely across the stem just beneath a node. Remove the leaves on the lower half of the cutting and dip the base of the cutting into a rooting powder. The best method of applying the powder is to spread a little on a sheet of plastic or wax paper, and dip the base of each cutting in this, them shake off any surplus and plant the cutting immediately. The cuttings can be rooted in potting mix of two parts coarse perlite to one part sphagnum peat.
The double-pan technique is an easy and successful way to do rooting cuttings. Use two flower pots, at least 4 inches deep with one so much larger than the other that when the smaller pot is set inside the larger one, there is a 2-inch space between their rims on all sides. The inner pot should be clay, the other pot plastic. Plug the hole in the bottom of the smaller pot with a cork and set the pot in the bigger one so their upper rims are level. Fill the space between the two pots with potting mix and insert the cuttings. Water with a fine spray and fill the inner pot with water. Cover the cuttings and pots with a clear plastic bag and place in bright, but indirect light. No further overhead watering is necessary. Sufficient water should pass through the porous sides of the small clay pot to maintain the potting mix in a moist condition. Keep the small pot full of water. If moisture collects on the inside of the plastic bag, open it to provide a bit of ventilation. The cuttings will produce roots in two to five weeks. When they are rooted, they can be planted outdoors in a protected location.
Kyle Schulz is a Wadena County Master Gardener from Sebeka, and the regular gardening columnist for the Wadena Pioneer Journal.