Helianthus (Sunflowers)

Sunflowers in the Asteraceae family are easy to grow and favored as highlights in summer gardens. With spectacular heights and blossoms that turn their heads to follow the sun, they have also become a sought-after element for involving children in gardening.

Growth Habits

By late-summer, sunflowers can reach more than shoulder height with large or small flower heads in a wide range of colors. Some make shorter, bushier plants with surprisingly colorful heads.

• They may be grown in forest-like clumps, in rows to make summer screens, or as stunning features shooting high above much smaller plants among garden beds.
• Tall, dinner-plate-sized annual sunflowers on a single stalk epitomize the notion of sunflower. While fun to grow, these annuals often require staking and plenty of space, lacking in many gardens. These are common in commercial productions.
• Most varieties develop a rather coarse aspect, true to their wild origins.
• In exposed, windy sites, unless taller types with large flowers are staked, they will bend or be blown over.
• Snails and slugs can be picked off young plants if they become bothersome. Other than that, sunflowers are delightfully uncomplaining and easy to grow. 

Planting and Harvesting Sunflowers

Growing sunflowers for cut blooms is best done in a section of garden put aside especially for this use. You can then take as many as you wish without spoiling the display.

• As their name suggests, sunflowers are best planted in full sun, although some late afternoon shade is helpful in hotter parts of Sonoma County.
• Because high yields take priority over design, place plants close together and avoid using nitrogen-rich fertilizers that promote leaf formation at the expense of flowers.
• Fast-draining soil with added compost is best.
• Once planted, they require little more than an annual cutting to the ground after flowers are spent or when perennial types go dormant in winter.
• Pick sunflowers early in the day after dew has dried. Remove leaves low on the cut stem, leaving just two or three higher up near the flower's face.
• Place stems in a bucket filled with water and allow them to rest for several hours in a cool area before placing in a vase.
• Change the water every few days. Blooms can last up to two weeks.

Main Attractions

All types are valued for their cut flowers and for attracting bees and birds that devour the large seeds. Small varieties are suitable for the front of a border or in containers while tall types are best in a separate, designated space where they have room to spread.

• Annuals comprise the vast majority of sunflowers. They must be seeded (or grown from small transplants) each year. There is a much wider variety of color and bloom size among the annual varieties, but they do not lend themselves to integration with the rest of the garden nearly as well as the perennials and are generally grown for flower cutting. A few popular annual cultivars of Helianthus annuus include:
  • 'Big Smile,' an aptly named midget that won't grow above 1 ft. high.
  • 'Teddy Bear,' a fast-growing annual that produces downy, double blooms on short, 2-ft. tall stems.
  • 'Delta Sunflower,’ a wonderfully big and prolific native that grows in the San Francisco Bay delta. It reaches 6 ft. tall and 4-5 ft. wide and blooms for months in a great show in the garden.
  • 'Velvet Queen,' adorned with sumptuous velvet-red petals surrounding chocolate centers on tall, free-flowering growth to 5 ft. high. 
  • 'Pastiche,' multi-stemmed plants that bloom in mixed shades of reds, yellows and buffs that blend nicely together. Groups of stems make a very effective screen 4-5 ft. high.
  • 'Moonwalker,' grown for its yellow face with a chocolate dark center, best at the back of a border where it reaches a height of 4-5 ft.
  • 'Russian Giant,' a spectacular tall cultivar 10 ft. high with a single huge face of yellow petals surrounding its dark center.
• Perennial species come back year after year after being cut to the ground when dormant in winter. They bounce back in spring, often in tall, expanding colonies. In late mid-to-late summer, they burst into dramatic blooms.
  • Helianthus angustifolius, swamp sunflower, grows 6 ft. tall with a much-branched stem and rough, sandpapery leaves 3-6 in. long, but only ½ in. wide. The perky yellow flowers, 2-3 in. across, are borne profusely in late summer and autumn. Moderate water is needed.
  • Helianthus gracilentus, slender sunflower, is a long blooming California native that is quite refined with slender, branching hairy stems to 6 ft. tall and nearly as wide. It bears hundreds of cheery 2 in. bright yellow daisies May to October. Once established it is completely drought tolerant and deer resistant.
  • Helianthus laetiflorus, showy sunflower, grows 4-8 ft. tall filled with yellow blooms on long stems very late in the season from August thru fall. Drought tolerant once established, this perennial travels annually by underground stems and is best planted where it has considerable room to spread.
  • Helianthus maximilianii, prairie sunflower, originated in the Midwest. It is another 6-10 ft. showstopper that bears huge numbers of 3-4 in. golden yellow flowers. It tolerates nearly any soil type, requires little water, and also spreads by rhizomes to form colonies that require ample space.
  • Helianthus salicifolius, willow leaf sunflower, grows 5-6 ft. tall and 3 ft. wide and produces clusters of 2-2½ in. bright golden blooms with dark centers. The unusual long, drooping, willow-like leaves surround vertical stems, helping to make it a stunning vertical accent that sways beautifully atop the stalks. It is not fussy about soil as it spreads to form dense colonies.

August 2023