Cornflower seeds are easy and inexpensive to grow in the home garden. Although they are best known for their cornflower blue blooms, these annuals also come in shades of pink, white, red, lavender, and maroon. Ranging in height from 10 inches to 2-1/2 feet, cornflowers produce single or double flowers with fringed petals and gray-green leaves. Dwarf varieties are suitable for edging and borders, while taller varieties are popular in cottage gardens. However, since taller varieties may not be readily available at local nurseries, planting cornflower seeds is the only way to get them in the garden. Fortunately, they're easy to grow both indoors and outdoors.
Planting Cornflower Seeds Outdoors
In areas with mild winters, annual cornflower seeds can be sown outdoors in September. They will begin to grow that season and will bloom in the following spring. However, for colder climates, plan on sowing cornflower seeds in spring as soon as weather permits. Several successive plantings of cornflower seeds will result in near-continual production of blooms throughout the growing season. This is because annual cornflowers are not long-lived plants. Garden experts recommend a second planting in spring if cornflower seeds are first sown in fall.
Sow seeds in a slightly alkaline garden soil to a depth of half an inch. Water well and keep the seeds moist until germination, which will happen in roughly seven to 10 days for annuals and in two to three and a half weeks for perennial varieties. Also, for annuals, keep the plants crowded. For perennials, thin them out so they're spaced about two to three feet apart.
Planting Cornflower Seeds Indoors
Cornflower seeds are easy to sow indoors as well as outdoors. Watch the calendar and plant them accordingly, about one month before the last frost or about a month before you're planning to set them outdoors.
Fill growing containers or peat pots with your choice of growing medium. If you're unsure what to use, just ask any store associate wherever you purchased the seeds for recommendations. Once the containers are filled, moisten mixture and allow it to drain. Then, sow three to four cornflower seeds per pot and cover with another 1/2-inch of growing medium. Mist the top lightly with water, and then cover your containers with plastic bags or sheeting. Place them in a warm location to allow seeds to germinate.
After seed germination, remove the plastic and place the containers under grow lights or in a sunny location. Once seedlings reach about two inches tall—and have one pair of true leaves—choose the strongest seedling to keep and pinch off the others at soil level. Use a water-soluble fertilizer once on all the containers, and finally, transplant seedlings outdoors when they are four inches tall (or less).