Bright yellow sunflowers are the poster flower of summer. Sunflowers are native to North America, but they are very often associated with the Mediterranean area. The flowers have a wide central disk surrounded by shorter petals. Sunflower's sturdy stems can grow 10 feet or more and may hold single flowers or be multi-branched. The seeds are edible and are favored by birds. They are also used to make oil and as livestock feed.
There's a reason they're called sunflowers. The flower heads follow the sun. So give some thought to where you plant your sunflowers. If you plant them on an east/west axis, you will be looking at the back of the flower heads for most of the day.
Traditionally, sunflowers were a sunny yellow color with a darker central disk. However, now we have a choice of rich chocolate browns, deep burgundy, and luscious multi-colored flowers.
Traditional sunflowers are annuals (the species name annuus should give us a hint), so they do not have a USDA Hardiness Zone rating.
For the best flowering and the sturdiest stems, plant your sunflowers in full sun. Since they are heliotropic, their flower heads will turn and follow the sun all day, so a full sun exposure will help them grow tall, rather than bending toward the light.
Most sunflower varieties begin to bloom in mid-summer and continue for several weeks. Fall is actually a bigger season for sunflowers than summer.
Garden Design Suggestions
Be careful when growing the taller varieties of sunflowers, because they can easily shade other plants. Tall sunflowers work best as a screen or in the back of a border. They're also great for growing vines on.
Shorter dwarf varieties can be more easily worked into a garden border.
If you are growing sunflowers for cutting, choose a multi-branched variety to get the most blooms. Whichever variety, plant in clusters of at least 9 plants, for the best impact and so that they can support each other to help prevent them from getting knocked down by wind or rain.
Varieties to Grow
Wonderful new varieties come out every year. Here are a few standouts:
- "Russian giant": A single yellow flower that can be 20" across. Great for seeds (10 to 12 ft.)
- "Teddy bear": A great dwarf variety with a fluffy flower head. Nice for containers. (1 to 2 ft.)
- "Giant sungold": This is a 5 ft. version of "Teddy bear".
- "Autumn mix": These are tall growers that give you a rainbow of fall colors on large flower heads. (6 ft. or more)
- "Italian white": These are creamy white flowers with great seeds for the bird feeder. (4 ft.)
- Prado series: These have shades of burgundy. Multi-flowered and early blooming. Great for cutting.
The flowers should begin to mature in early fall. When this happens, the heads will turn downward and the florets in the center disk will shrivel. The only sure way to tell if the seeds are ready to harvest is to pull a few out and open them. If they are full, they're ready. Don't wait too long or squirrels and birds will harvest for you.
To harvest, cut the whole flower head with about 1 ft. of stem attached and hang in a warm, dry, ventilated spot, away from insects and rodents. Cover the seed heads with cheesecloth or a paper bag, to catch loose seeds. Poke some small holes in the paper bag for ventilation. When the seed is completely dried and ready for use, it can be easily rubbed off the flower head and collected.
Sunflowers are usually grown from seed. Seed can be direct seeded in the garden, once all danger of frost is past, or they can be started indoors 3 to 4 weeks before transplanting. Peat or paper pots are recommended for seedlings started indoors, because sunflowers do not like to have their roots disturbed. Transplants often grow faster and flower sooner than direct-seeded plants so you could lengthen your bloom period by doing both.
Plant seeds 1 to 3 inches deep and 6 to 12 inches apart. Taller varieties should be thinned to about 1 to 1/2 ft. apart. Dwarf varieties can be planted about 1 ft. apart.
Birds and other animals are attracted to sunflower seedlings, so some protection when they are young is suggested. Cover them with row covers or screening and remove when plants are a foot or two high. An easy temporary way to cover them is to use one of the webbed plastic trays from the garden center. Remember to remove it before the plants grow through it.
Sunflowers like well-drained soil with a good amount of organic matter. They are extremely fast growers and appreciate a fertilizer high in phosphorous and potassium, (the middle and end numbers on the fertilizer package), to remind them they're supposed to set flowers on those tall stalks.
- Watering regularly will help them set flowers. They will stop blooming during periods of drought.
- Sunflowers do not like to compete with weeds. Mulching will help with both soil moisture and weed suppression. And don't forget that sunflowers need a lot of sun.
- Most sunflowers get top heavy when they bloom and can use the support of staking. If they are planted very close together, they may support themselves, but usually, heavy rain or strong wind will cause them to lean and they won't straighten up on their own. Planting sunflowers along a fence is the easiest way to stake them. Bamboo stakes are also strong enough to keep them upright. Use care when inserting the stakes, so you don't damage the sunflower roots.
Pests and Problems
- Birds and squirrels: Use frightening devices or cover the flower heads with netting.
- Sunflower moth: Lays its eggs on the plant and the larvae feed on the flower heads, tunneling and leaving holes in the seed.
- Aphids and whiteflies can also be pests, but what don't they like?
- Fungal diseases: These include sclerotinia (white mold), downy mildew, rust. To avoid, provide adequate air circulation.
- Verticillium wilt: You'll see dead areas in between the leaf veins, with yellowish margins. Choose resistant varieties.
The best control of diseases is prevention, by changing where you plant each year and disposing of any infected plants. And if you're worried about squirrels or other animals getting the seeds before you, try growing them in the vegetable garden. Flowers in the vegetable garden are great for attracting more pollinators. To further foil squirrels, plant a coarse-leaved vegetable, like squash, at their base.