Check out local nurseries for seedlings, which are widely available. Gomphrena also is relatively easy to start indoors from seed.
Plant seedings outdoors any time after your region's last average frost date.
Plant seeds indoors six to eight weeks before the last frost date. Soak seeds first for 24 hours to speed germination.
Pinch off first flowers to create bushier, healthier plants with more flowers in the long run.
Pull up and discard plants in autumn, once frost has felled them.