Sunflowers flourish at the LSU AgCenter Hammond Research Station. (Photo by Allen Owings)

A squirrel feeds on a sunflower (Photo by Dan Gill)

For Release On Or After 07/18/14

By Dan Gill
LSU AgCenter Horticulturist

If you haven’t paid a lot of attention to sunflowers for your garden lately, you may think only of the gigantic sunflowers that reach for their namesake in the sky – towering to heights of 8 feet or more. And you may think that they only come in yellow.

But today’s gardener has a lot of choices when selecting sunflowers for color, height and use as cut flowers. In addition, sunflowers that produce edible seeds are great for providing a late-summer crop of sunflower seeds.

Sunflowers are among the easiest flowers to grow and thrive in the heat of the summers here. As many people have noticed, sunflowers often come up from seeds put out as bird food – so how hard can they be to grow? This quick easy growth is why children are often so delighted with sunflowers.

Depending on the variety, sunflowers will bloom anytime from about 55 to 75 days after planting the seeds. (Check the seed package information.) Sunflowers can be broadly divided into those grown for edible seeds and those grown as ornamentals and for cut flowers.

You can start sunflower seeds in small containers with drainage holes and filled with potting soil. Locate the containers in full sun to produce strong, stocky transplants. Make sure you water regularly and never allow the soil to become dry. When the seedlings have grown 4-6 inches high, transplant them to sunny flower beds.

You can also sow the seeds directly into a prepared garden bed in full sun. After sowing the seeds, water the bed well, and then water the bed as needed to keep the soil moist. The soil must stay moist for the seeds to reliably germinate and grow.

When preparing a bed for either transplants or direct seeding, incorporate a 2- to 4-inch layer of organic matter (compost, rotted leaves, bagged manure) and a light sprinkling of general-purpose fertilizer into the bed. When planting transplants, water them in with a soluble fertilizer mixed with water half strength. To encourage maximum growth, fertilize with a soluble fertilizer once or twice a month, or apply a light application of the general-purpose fertilizer about six weeks after planting the bed.

A  cut above

Sunflowers grown for cut flowers generally produce numerous flowers on a bushier plant than those grown for seeds, which generally produce a single, large head. The multiple-flowering habit makes the cut-flower types fit into traditional flower beds more appropriately. While brilliant yellow will always be popular, you can also choose from creamy white, bronze, mahogany, rusty red, burgundy and orange, with some types producing flowers with more than one color.

Cut sunflower blossoms before they are fully open and place them immediately into water. Shedding pollen is sometime a problem (the pollen can stain fabric if it gets on it), and several varieties for cut flowers have been bred not to produce pollen. A few pollenless varieties include Chianti, Strawberry Blonde and Sunny.

The seedy side

If you want to grow sunflowers for the delicious, nutritious seeds, make sure you choose cultivars bred for seed production, such as Mammoth Russian (also known as Mammoth, Russian Giant and Gray Stripe). These tall-growing sunflowers produce a single, enormous flower at the top of the plant. To grow a really big seed head, apply general-purpose fertilizer when the flower head begins to appear.

When growing tall sunflowers, you may want to provide a tall, strong stake driven well into the ground for support. As the seed heads mature they get heavier, and strong winds may blow the plants over.

As the seeds mature, you have to make a choice about whether you want the seeds all to yourself or if you are willing to share them with the birds and squirrels. If you don’t want to share, you will have to cover the seed heads with cheesecloth or an old nylon stocking to keep the animals at bay. Watch the birds; when they start to visit, it is time to cover the heads.

Seed heads are ready to harvest when the bracts behind the head turn brown and the back of the head is greenish yellow to yellow. Leave about 1 foot of stem attached, and hang the seed head in a warm, well-ventilated place.

When the back is entirely brown, remove the seeds by brushing them out with your hands or a stiff brush. Do not wash the seeds before storage because this might promote rot. Store the seeds in air-tight containers in your refrigerator to maintain flavor and nutrition.

Share the wealth

Sunflower seeds are also excellent food for birds and other animal life in your backyard. Once the seed head has matured, you can simply leave the plants in the garden for the animals to have fun with, or you can cut it off and hang it someplace convenient for you to watch wildlife visit and eat the seeds.

Rick Bogren