Growing sunflowers in Iowa is a great way to enjoy the beauty of the summer season. Not only are sunflowers a beautiful addition to any garden or landscape, but they are also great for attracting bees, butterflies, and other beneficial insects. Iowa’s warm summer temperatures, ample sun, and rich soil make it the perfect place to cultivate these bright and cheery flowers.
Sunflower plants are easy to grow and require minimal upkeep, making them a great choice for busy gardeners. With a little bit of care and attention, sunflowers can provide you with a vibrant and cheerful addition to your garden that will last throughout the summer and into the fall.
Iowa’s climate and growing zones
Growing Zone 4 covers the northernmost part of the state and has a short growing season. Average annual temperatures range from -20 to 30 degrees Fahrenheit. The last frost date in spring is typically around May 1st and the first frost date in fall is usually around October 15th.
Growing Zone 5 encompasses the northern and central parts of the state. Average temperatures range from -10 to 40 degrees Fahrenheit. The last frost date in spring is typically around April 15th and the first frost date in fall is usually around October 30th.
Growing Zone 6 covers the southern and central parts of the state. Average temperatures range from 0 to 50 degrees Fahrenheit. The last frost date in spring is typically around April 1st and the first frost date in fall is usually around November 15th.
Growing Zone 7 covers the southeastern part of the state. Average temperatures range from 10 to 60 degrees Fahrenheit. The last frost date in spring is typically around March 15th and the first frost date in fall is usually around November 30th.
Growing sunflowers in Iowa
In the spring, the soil in Iowa should be tilled and amended to a depth of at least 8 inches. Planting in the early summer will provide the best chance for success. Sunflowers prefer direct, full sun and well-drained soil with a pH of 6.5 to 7.0. A good compost or fertilizer may be needed to improve the soil’s fertility.
When the soil is warm enough, usually in late May or early June, it is time to plant sunflower seeds. Plant in rows, spacing the seeds 6-12 inches apart, and cover with 1-2 inches of soil. Water the seeds in a well and keep them consistently moist until they have germinated.
In Iowa, late summer and early fall are the best times for harvesting sunflowers. When the seed heads turn brown and the petals dry, the flowers are ready for harvesting. Cut the stems about 6 inches from the head and hang the flowers upside down in a cool, dry place. After a few weeks, the seeds will be ready to separate from the head.
Although Iowa winters can be cold and harsh, sunflowers are generally able to survive. If a heavy snowfall or freeze is expected, cover the plants with a thick layer of mulch or straw to protect them. Otherwise, the sunflowers should be able to survive the winter and start growing again in the spring.
Some of my favorite varieties of sunflower include:
- Mammoth Grey Stripe Sunflower (Helianthus annuus) – 75-100 days to maturity
- Teddy Bear Sunflower (Helianthus annuus) – 60-90 days to maturity
- Red Sun (Helianthus annuus) – 65-95 days to maturity
- Autumn Beauty Sunflower (Helianthus annuus) – 75-90 days to maturity
- Lemon Queen Sunflower (Helianthus annuus) – 75-95 days to maturity
- Velvet Queen Sunflower (Helianthus annuus) – 90-110 days to maturity
- Dwarf Sunspot Sunflower (Helianthus annuus) – 60-90 days to maturity
- Giant Sungold Sunflower (Helianthus annuus) – 85-110 days to maturity
- Evening Sun Sunflower (Helianthus annuus) – 75-95 days to maturity
- Sundance Kid Sunflower (Helianthus annuus) – 75-95 days to maturity
When to start sunflowers indoors in Iowa
Sunflower seeds should be started indoors 4 weeks before your final frost date. In Iowa, the final frost dates are:
- Zone 4: Around May 12th
- Zone 5: Around April 30th
- Zone 6: Around April 21
- zone 7: Around April 3
You should also consider the size of the variety of sunflower you are planting, as shorter varieties can be planted later and taller varieties will need to be started a week or two earlier. Sunflowers should be started indoors:
- Zone 4: Around April 14th
- Zone 5: Around April 1st
- Zone 6: Around March 24th
- zone 7: Around March 6th
Starting sunflowers from seed is a relatively easy process that can be done both indoors and outdoors. To begin, you will need to purchase sunflower seeds from a garden center or online. When selecting seeds, make sure to look for the desired variety you want to grow. Once you have your seeds, you can choose to start them indoors 4 weeks before the last frost date for your region.
Fill a seed tray with starter soil and moisten it with a spray bottle. Place your seeds on top of the soil, cover them lightly with starter soil, and water them gently. Place the tray in a warm and sunny spot, and keep the soil moist. Once your plants have grown 2-3 sets of leaves, you can transplant them outdoors.
Planting sunflowers outside in Iowa
Sunflower seeds should be planted outdoors after the last average frost date for your area. Planting sunflower seeds too early can result in poor germination and seedling growth and potentially death if there’s a hard freeze.
When planting outdoors, make sure the area has plenty of sunshine and well-draining soil. Dig a hole that is twice the size of the root ball, and fill the hole with compost or aged manure. Place the seedling in the hole and backfill with soil, then water deeply.
For the remainder of the sunflower’s life, make sure to keep the soil moist and fertilize regularly. With proper care, you should have beautiful sunflowers in no time!
When to harvest sunflower seeds in Iowa
When sunflower seeds are ready to be harvested, the back of the flower head will be dry and start to turn brown. The individual seeds will be dry and firm. The green husks surrounding the seeds will have turned yellow or white and begun to dry out. To check if the seeds are ready to be harvested, lightly pinch the seed head between your thumb and forefinger. If the husks break open easily, the seeds are ready to harvest.
Harvesting sunflower seeds is easy. Cut the flower head off the stem and spread it out on a clean surface. To remove the seeds, use your hands to rub the flower head and release the seeds. Collect the seeds in a large bowl or container. Once the seeds are harvested, store them in an airtight container in a cool, dry place. Make sure the container is well sealed to keep the seeds from going bad. Sunflower seeds can last for up to a year if stored properly.
Sunflower seeds are delicious and nutritious snack food. They can be eaten raw, toasted, or sprouted. Sunflower seeds are also used in salads, cereals, granola, and energy bars. They are loaded with essential vitamins and minerals like Vitamin E, phosphorus, magnesium, and zinc. Sunflower seeds can also be used to make sunflower seed butter, which is a great alternative to peanut butter.
In addition to being a healthy snack, sunflower seeds are also used to make birdseed. You can leave your sunflowers intact outside well after the flowers have died to give your local birds a tasty snack!