Milkweed In The Fall. Spring planted seeds need to be chilled in the refrigerator which replicates the natural process of snow and cold breaking down the seed casing. Even if the cold kills the stems it may regrow quickly from the roots.
Find seeds here if you still need to buy some. In late summer and fall these pods split open spewing seeds that re seed the plant. Planting in the fall allows for natural stratification cold treatment so the seeds will germinate the following spring.
For this reason i prefer to cut milkweed back in spring.
Learn more about prechilling seeds before planting. Clear away any mulch or rocks from the area which could potentially block the growth of a small seedling. Learn more about prechilling seeds before planting. Whether you cut back your plants in fall or spring is totally up to you.