The sunflower (Helianthus annuus) is an annual plant native to the Americas in the family Asteraceae, with a large flowering head (inflorescence). The stem of the flower can grow as high as 3 metres tall, with the flower head reaching up to 30 cm in diameter with the “large” seeds. The term “sunflower” is also used to refer to all plants of the genus Helianthus, many of which are perennial plants. Few flowers are more cheerful than sunflowers. Bursting into bloom in late summer, they’re an excellent addition to any garden. There is now an amazing array of sunflowers in a range of heights from 6 inches to 6 feet and in every color of the sunset.
What is usually called the flower is actually a head (formally composite flower) of numerous flowers (florets) crowded together. The outer flowers are the ray florets and can be yellow, maroon, orange, or other colors, and are sterile. The florets inside the circular head are called disc florets. The disc florets mature into what are traditionally called “sunflower seeds”, but are actually the fruit (an achene) of the plant. The true seeds are encased in an inedible husk.
Sunflowers in the bud stage exhibit heliotropism. At sunrise, the faces of most sunflowers are turned towards the east. Over the course of the day, they move to track the sun from east to west, while at night they return to an eastward orientation. This motion is performed by motor cells in the pulvinus, a flexible segment of the stem just below the bud. As the bud stage ends, the stem stiffens and the blooming stage is reached.
Sunflowers look good planted individually, in rows, or in groups. For individual planting, put the seedling or seeds in just about any sunny location. Plant either individual, in groups, or in patterns. Tall varieties should go to the back of the flower garden. Smaller types are usually placed in the front as a border or edging. Make sure they are visible from your deck, porch and windows. You will be able to enjoy watching a variety of birds as they enjoy the seeds in late summer.
To grow well, sunflowers need full sun. They grow best in fertile, moist, well-drained soil with a lot of mulch. In commercial planting, seeds are planted 45 cm (1.5′) apart and 2.5 cm (1″) deep.
Sunflowers can be started indoors, or sown outdoors directly into the garden. It is good to start them indoors only because squirrel and birds like to search for, and dig up, the seeds. If you have this problem and want to sow them directly in your garden, try placing an old screen over them after you plant them.
If you want to achieve the maximum height of a flower, rather than the biggest bloom, make sure you select an area in your garden where the sunflower’s (sprouting) bloom can’t search for the sun all day long. If it can head for the sun from sunrise to sunset the sunflower will choose to grow a bigger bloom rather than grow really tall (it wants to achieve as many offspring as possible and all energy going into seed-production will be deducted from plant-growth). Just make sure the sunflower will fall into (for example) a wooden fences shadow during the early hours of the day and the evening hours. The key is to have it catch the 6-8 hottest hours of sunlight every day and than be casted into (moderate) shadow.
Sunflowers grow in most soils. The soil needs to be lose enough for them to grow wide, deep roots to support this tall plant in winds. If you are growing a tall variety, stake them to protect them from high winds. Sunflowers grow well in average to rich soils. If you have a choice, sandy soils are not recommended, as they are easily uprooted in loose soil. Rich soil is important, when growing giant varieties.
Once your sunflowers get started, they are a low maintenance plant. They will withstand droughts, but adding water will help them. They don’t need a lot of fertilizer. And, weeds are not a problem once they get a couple of feet tall. If you would like to make the sunflower be bigger, would be good to fertilize the land or add compost or humus before seeding and the liquid fertilizer or the chemical fertilizer after sprouting from the soil. And spread fertilizer once for a week on the land. In case of a potted plant, do it once for two weeks. More times giving a little amount of fertilizer, more splendid flowers you can make bloom.
When the plant is above ground, give it a lot of water during sunny days, but keep your eyes on the local weather reports for rainy days, do not water at least a day before then, cause during rainy days the sunflower can’t deal with the excess water (it can’t use it because there is not enough sunlight energy to let it suck it up) and can soften the roots (which can result in a collapsing of the plant.) Once a week, use liquid fertilizer to replenish the soil with nutrients. A fast-growing sunflower really drains it’s soil).
Harvest sunflower seeds after the flower begins to die back, and most if not all, of the petals have fallen off. Pull out a seed and open it to see if it is full. Cut off the head, leaving a few inches of stalk. Hang the stalks to dry in a well ventilated area. Do not stack them in a box, as mold can develop during the drying process. As soon as the flowers have dried, extract the seeds by rubbing two flower heads together. They should come off of the flowerhead fairly easily.
Sunflowers do great in containers. Plant seeds in full sun, using a light potting soil or soil-less mix. Plant the seeds to a depth of 1 inch (6 inches apart) and expect to see them germinate quickly. Days to maturity will vary according to each variety. Seedlings of regular varieties will need to be thinned to 12 to 18 inches and given plenty of room to grow and spread out. Dwarf varieties can be packed in a little more closely together, but still need to be spaced at least 4 to 5 inches apart. Sunflower roots are quite large and like to spread out. Mammoth varieties grow best in half barrels or containers that are at least 66 to 18 inches deep and 12 inches wide. Smaller containers will keep plants from reaching their full growth potential. Sunflowers grown in containers need to be watered daily and even more frequently during really hot weather. Feed them a 1/2 strength water-soluble fertilizer every other week or so to support big blooms, and mulch around the tops of the containers to help conserve moisture.