Butterfly bushes can be planted by using seeds, cuttings or by transplanting already established bushes. Before planting any of these incarnations of the butterfly bush, first make sure the soil where you will ultimately place the butterfly bush is well-drained and is nourished with compost.
To plant seeds, gather them in the fall when the bush produces its seeds. Place the gathered seeds in a paper bag and put them in your freezer for about four weeks before you plant them. The seeds need this refrigeration to mature properly so they will be able to germinate.
Once the seeds have been properly chilled, they must be planted where they will receive full sunlight, either in pots or in the ground. Just barely cover them with soil so they will receive enough light to germinate. Keep the soil moist, but not too wet. It will be months, not weeks, before you will see a seedling from each seed. Once they sprout, they need to be allowed to grow until they are healthy and sturdy enough to transplant.
You can easily propagate butterfly bushes from cutting off healthy branches in spring or summer. Cut branch pieces that are at least three inches long by making an angled cut so the branch will absorb nutrients more easily. Strip the bottom leaves from the cutting.
Dip the angled cut into rooting hormone, available at your garden center, and insert it into moistened potting soil or a mixture of peat and sand. During the rooting process, the cuttings must be kept in a shady area instead of full sun like the seeds and established butterfly bushes need. Keep the cuttings warm and moist for a few weeks, which is when roots will begin to form. When the roots become healthy and more established, move the cuttings into the sun, keeping them evenly moist until they adjust to their new environment and are growing well. Then, they can be transplanted into their final destination. Make sure to keep them moist while they adjust to their new location.
You can also dig up established butterfly bushes and divide them at their roots and transplant them in other locations in your yard or garden. To divide butterfly bushes, either in the spring or fall, carefully dig up the established bushes and brush off most of the soil. Carefully break the roots apart by hand or with a shovel. The divided bushes can then be transplanted into pots or in their final destination in your yard.
Once the seedlings, cuttings, divided bushes, or purchased bushes are ready to plant, prepare the soil in full or almost full sun. Cultivate the soil about 12 to 15 inches deep and work in about 4 inches of compost. Dig a hole for each bush twice the diameter of each pot. Gently tap each bush out of its pot and plant it in its hole so the top of the roots are even with the surface of the soil. Fill in the hole with soil and pat it down around the bush. Thoroughly water the bush and keep the soil moist.