The potato bush Lycianthes rantonnetii, also known as Paraguay nightshade or blue lycianthes, is classified as a tropical shrub or tender perennial and is hardy in U.S. Department of Agriculture zones 8 to 11. It grows to heights of 4 to 6 feet with a spread of about 5 feet. The potato bush has blue-violet or purple flowers, and it flowers repeatedly. Take cuttings from mid-July to early fall.
Water the shrub the evening before taking any cuttings.
Fill a 6-inch pot with well-drained potting soil. Three or four cuttings can be put into each pot. If you will have more cuttings than that, fill as many pots as you will have cuttings to fill.
Examine the stem of the potato bush in the morning to find where the stem color changes from green to brown. The semi-hardwood is formed on the current season's growth. The wood will be firm and the leaves will be normal size.
Cut a 4- to 6-inch cutting with pruning shears where the stem has semi-hardwood. Cut the stem right below the leaf node.
Remove the leaves from the bottom half of the stem. Leave at least 2 leaves at the top of the cutting.
Dip the cut end in a glass of water. Shake the cutting to remove the excess water.
Dip the wet end into rooting hormone. Shake the cutting to remove the excess rooting hormone.
Poke 3 to 4 holes into the potting soil with a pencil. Space each hole equally.
Insert the end of the cutting with the rooting hormone into the hole. Firm the soil around the stem with your fingers to hold it in place.
Water the soil until thoroughly saturated. The water will run out the drainage hole at the bottom of the pot.
Place the pots on a rack over a container so all the water can drain away into the container below.
Place a clear plastic bag over the top of each pot.
Place the pots in a warm, bright area. Do not place them in direct sunlight or the cuttings will become too hot.
Check the soil daily and add water to keep the soil moist. Do not add so much that the soil is soggy, or the cuttings will rot.
Test the cuttings after a month for roots by pulling gently on the stem cutting. If it moves easily, the roots have not formed. Remove the plastic bag when the roots have formed.
Transplant the cuttings into individual pots when their roots are 1/2 to 1 inch long. Keep the planting depth the same and continue to grow them in a bright location. Continue growing the cuttings in containers for 1 year to increase their chances of survival.