Cut dead branches off the plant in late spring. The Butterfly Bushes website recommends doing this in June. Worthington City Schools in Ohio suggests trimming 50 percent of the milkweed back by half at this time, too.
Deadhead the plant every couple of weeks in summer. This will let the plant continue to concentrate on flowering instead of producing seeds.
Trim the entire plant back to less than 4 feet high in late fall.
Inspect the plant every year to find older stems that now appear “woody” toward their bases; cutting these off at the base of the stem will let the plant produce new growth.