What Should You Do With Sunflowers After They Bloom?

The yellow faces of sunflowers (Helianthus spp.) are a symbol of the bright, sunny days of summer. Different types of the sun-loving, thirsty flowers grow in both annual and perennial gardens. They can be used for decorative purposes, or their seeds can be harvested as part of a summer garden crop.

Sunflowers can be annual or perennial. Annual flowers can have either small or large seeds, bloom in late spring the year they are planted and have stringy roots. Perennial versions are generally smaller in size, grow in early spring clumps of flowers, have small seeds and roots grouped as knotty rhizomes and can be found throughout U.S. Department of Agriculture plant hardiness zones 3 to 9. Both types of sunflowers can produce edible seeds, although it is the largest of the species that have the best seeds for snacking.

Two examples of these are the cultivars "Maximilian" and "Mammoth." The perennial "Maximilian" (Helianthus maximiliani) is a tall, native prairie sunflower that blooms from August through November. It can be found across USDA zones 4 through 9. "Mammoth" (Helianthus annuus "Mammoth") blooms over the summer with traditional bright yellow heads up to 1 foot across. Growing up to 12 feet tall, these fast and easy-to-grow flowers provide plentiful seeds at harvest time.

Cut sunflowers can be used for decorative purposes in flower arrangements. In the morning hours, cut young flowers whose buds have not fully opened, leaving at least 1 foot of stem. Annual flower heads are very heavy and can droop and break without support. Slide on plastic stem supports or tie the upper stems to a wooden dowel to prevent breakage. Immediately place the freshly cut stems in a vase of water. Sunflowers can last a week if kept well hydrated. Flowers you chose not to cut should be supported with garden stakes and ties to prevent wind damage.

While sunflowers are beautiful to look at, their seeds are also a valuable crop. To harvest the seeds for use, wait until the back of the flower heads turns yellow, then dries and turns brown. This is generally 30 to 45 days after bloom. Once the seeds are dried, cut the head off about 4 inches down the stem. Remove the seeds using your fingers or a fork.

When you are leaving the heads on sunflowers to dry outside, they can become a temptation for outdoor animals like birds and squirrels. To protect the heads, cover them in a light breathable fabric like cheesecloth and secure it with a twist-tie below the head. Alternatively, you can cut the flower head early along with at least 2 feet of stem and bring them inside to dry. Hang the heads upside down in an area where pets or indoor pests can't get to them.

With many cultivars of sunflowers available, there are many sizes of seeds as well. Smaller flowers with small solid black seeds are generally used for animal and bird feed or by industry for making oils. Larger, striped seeds are best for human snacking. To prepare these larger seeds to eat, soak them overnight in 1 gallon of water mixed with 1 cup of salt. Dry them in an oven set to 250 degrees Fahrenheit for four to five hours. Store the salted and dried seeds in an airtight container.