Flowers conjure a variety of emotional and sensory responses as well as memories. Loving sentiments are often attached to roses. Violets are sometimes associated with youthful sweetness and a bouquet of daisies brings cheer into any room. Gladiolas often appear in funeral arrangements and the scent of lavender might stir memories of fields of flowers on a hot summer day. A sunflower’s appearance literally fills the space with sunlight.
Though the sunflower, Helianthus annus, has been widely cultivated to produce flowers with different colors, shapes and sizes, the basic structure of the inflorescence continues to be reminiscent of the sun.
Most varieties maintain an attraction to sunlight with heliotropic buds that move to follow the sun and mature flowers that face the rising sun in the east. The botanical name Helianthus is derived from the Greek words helios for sun and anthos for flower.
Sunflowers are members of the largest family of flowering plants, the Asteraceae family. Like most family members, sunflowers have composite heads consisting of hundreds of tiny flowers clustered in the center of rays of petals that can vary in size and color depending on the cultivar. The flowers on edible varieties produce delicious seeds when pollinated. Many ornamental cultivars have been bred for their long-lasting beauty as cut flowers.
The original sunflower was an oilseed plant native to temperate North America. It was transported to Europe in the 16th century and nearly 100 cultivars, including many ornamental varieties, have since been developed.
Several edible varieties are recommended for West Hawaii gardens. The most popular, and the largest, is the Russian mammoth. Russian breeding in the 1800s produced this giant with bright gold petals and heads that reach 10 to 12 inches across on 8- to 10-foot stalks. The flowers that make up the head result in gray and white seeds.
The edible snack seed hybrid is somewhat smaller, reaching about 6 feet. This variety produces deep golden petals and heads that produce plump seed kernels.
The dwarf sunspot only grows about 2 feet tall with single, yellow flowers 8 to 10 inches across. This long-lasting cut flower is also a great seed producer.
Most sunflower varieties have single heads, though some have lower branches that produce smaller, additional flowers. Sunflower leaves are ovate and on giant varieties can be more than a foot long. The leaves as well as the stems and the flower bracts are hairy.
Sunflower seeds are best sown outdoors directly into the garden. Cover newly planted seeds with a screen, however, as birds and other animals will sometimes dig them up.
If you plant sunflowers indoors, individual peat pots work best. Plant two seeds per pot and thin to the strongest one before planting outdoors. Sunflowers produce a strong tap root which helps them stabilize in the wind, so cut the bottom of the pot and plant them outside when the first true leaves appear. Their deep roots help them withstand most droughts as well so protecting them when transplanting is vital.
Sunflowers do well in full sun, though some varieties tolerate light shade. They are adaptable to poor soil and need little moisture though they also thrive in deep rich soil with regular watering as long as the soil drains well. They benefit from an occasional dose of fertilizer and you can promote bigger blooms by applying extra phosphorus and potassium when buds begin to develop.
Sunflower seeds can be a tasty snack for people or a high-protein addition to bird seed mix. Place bird feeders in areas that will not be affected by the allelopathic properties in the outer husk, however, which can kill grass or prevent other plants from growing where they drop.
Sunflower oil is used in cooking and can also serve as a carrier oil in producing margarine or biodiesel fuel. The leaves are used as cattle feed, as is the cake remaining after the seeds have been pressed for oil.
Careful inspection of the flower heads will show the flower and seed cluster always appears in a spiral pattern. Mathematicians have often marveled at this arrangement in a sunflower head. The spiral pattern is known as a Fibonacci sequence and for those interested in math, deserves further Internet research.
Sunflowers are susceptible to bacterial, fungal and viral diseases but most can be dealt with simply if caught early. Chinese rose beetles may attach to young plants but usually quit as the plants age. Keeping the soil and plants healthy can avoid most diseases and pest attacks.
Harvest sunflower seeds after the flowers begin to die and most of the petals have fallen off. Remove a seed and open it to see if it is full. If it is, cut off the head, leaving a few inches of stalk so it can be hung to dry in a well-ventilated area where mold is unlikely to develop. When the flowers have completely dried, rub two flower heads together to loosen the seeds and they’ll drop off fairly easily.
Sunflowers are easily propagated from seed. Find seeds online or at local nurseries and stores with seed racks. Look for some of the lovely ornamental varieties that will bring sunny color into your home or find an edible variety to add nutrition to your diet. Now is a good time to plant sunflowers as winter weather gets drier and sunnier.
Diana Duff is an organic farmer, plant adviser and consultant.