Cut sunflowers will last longer — up to about 12 days — if they are harvested at a certain stage of blooming and under specific conditions. In addition, the cut sunflower must be kept hydrated and well-fed at all times to ensure its longevity.
With proper selection and care, cut sunflowers can stay fresh for six to 12 days.
When to Cut a Sunflower
Prolonging the life of a cut sunflower starts by carefully choosing the right one to harvest. Look for a healthy, vibrant and sturdy plant with a flower with petals that point straight toward you. If the petals are fully open, it's hard to know how old the flower is, and the petals could be ready to drop in just a couple of days. A flower that hasn't quite opened yet has plenty of bloom time left.
In addition, plan to cut sunflowers in the morning. The cooler temperatures decrease the likelihood of the flower wilting.
How to Cut a Sunflower
In addition to sharp and sanitized shears, bring a bucket of room-temperature water with you when you're ready to cut a sunflower. It's crucial to keep the stem moist, or the flower will wilt and may not recover. Keeping the cut flower out of direct sunlight also helps prevent wilting. Attach a clamping umbrella to the bucket to help shade the flowers without crushing them.
Cut the stem about 2 1/2 feet (30 inches) below the flower. Immediately place the cut end in the bucket of water and ensure it stays in the shade until brought inside. Once there, you can measure the vase and determine how many additional inches to cut off the sunflower stem. Make the cut underwater in the bucket.
You can also cut off all but the topmost leaves. This ensures all of the flower's resources are focused on keeping the flower open and bright for as long as possible. If you notice any of the remaining leaves beginning to wilt over the coming days, immediately remove them.
Caring for a Cut Sunflower
Mix your own flower food by adding 2 tablespoons of lemon juice and 1 tablespoon of sugar to every 4 cups (1 quart) of water in the vase. The sugar will dissolve better if the water is warm, but it should be brought back to room temperature before the flowers are added. Add 1/2 teaspoon of bleach to delay mold and bacteria growth.
Replace the vase water every three days or sooner if the water threatens to dry up. To ensure the stem doesn't dry out during this process, temporarily place the flower in a second vase of plain water. Just before putting it back into its original vase, cut about half an inch off the stem to remove any scar tissue that may prevent water from entering the stem.
Finally, choose a cool location to display the cut sunflower. Hot and drafty conditions will decrease the sunflower's longevity, so keep it out of direct sunlight and away from vents or exterior doors. A dining room table, office desk or night stand is typically a good choice.