Plant the seeds only about ¼-inch deep. You'll see seedlings sprout in four to seven days. Once the seedlings reach about three inches tall, thin them so that they're 6 to 18 inches apart to maximize air circulation, a key to keeping zinnias looking good all season.

Zinnias are annuals, so they'll grow for one season and produce seeds, but the original plant will not come back in subsequent years. They have bright, solitary, daisy-like flowerheads on a single, erect stem, which makes them great for use as a cutting flower or as food for butterflies.

Seeds from open-pollinated plants, though, will grow true to the parent plant, so it makes sense to harvest those seeds. The following zinnia varieties are open-pollinated, meaning they will grow to look the same as the parent plants from which their seeds came: Green Envy. Cactus Bright Jewels.

A rule of thumb with seeds is if they are good, they will be hard, as you noticed with the seeds on the right, thick and ridged. Bad seed will be thin and easily bendable.. . . . .364011233508!]0000000000000009783314147683!]