How to Plant and Grow Perennial Sunflower

Probably one of the most-loved and familiar flowers in the world, sunflowers have long been a favorite for borders and bouquets alike because of their huge, brightly colored blossoms. While not quite as large as its annual cousin, the perennial sunflower (Helianthus spp.) makes up for what it lacks in size with tons of blooms in late summer and fall.

Perennial sunflowers can usually be found in varying shades of gold, with a few cultivars in a softer lemon yellow. The foliage differs among many of the sunflower species. While sunflower leaves tend to be coarse in texture, there are some exceptions, such as Helianthus salicifolius, which has fine foliage. These plants don't branch except at the flowering tips, creating an extremely soft and airy texture.

Many native perennial sunflowers in the United States are tough plants coming from the Great Plains, prairies, and open rocky woodlands. They are well-adapted to a variety of conditions.

Where to Plant Perennial Sunflower

Plant perennial sunflowers in an area that receives full sun. The soil needs to be well-draining. Plant smaller perennial sunflowers at the front of a border, while the taller ones belong in the middle or back of a mixed bed or a cutting garden.

If you plan on growing some of the taller varieties, make sure you stake them as they are prone to flopping, or plant them near other tall plants, walls, or fences for support.

How and When to Plant Perennial Sunflower

Sow perennial sunflower seeds directly in the garden in spring after the last spring frost date. Prepare the garden bed by loosening the soil to at least 1 foot deep and adding compost and organic matter. Make 1-inch-deep holes spaced 12-18 inches apart, and drop a seed in each hole. Cover with soil. Seeds sown in spring might bloom by fall, but possibly not until the following spring.

Seeds can be sown in fall in the same manner as spring-sown seeds. Following the natural cold stratification of winter, the resulting plants will flower earlier than spring-sown plants.

To get a head start on the season indoors, begin eight to 10 weeks before the last spring frost. Put the seeds in a plastic bag with moist seed-starting mix and place it in the refrigerator for a month. Then, fill small pots with moist seed-starting mix and put one seed in each pot. Place the pots in bright light in a warm, dry location until germination occurs. When the soil warms in late spring, harden off the seedlings and plant them outside.

Plant a few seeds every two weeks through spring and summer to enjoy continuous bloom.

Perennial Sunflower Care Tips

Light

To prevent legginess, plant perennial sunflowers in full sun. This encourages the most blossoms possible on the most compact habit. They will tolerate part shade but are more likely to develop fungal diseases such as leaf spots and powdery mildew.

Soil and Water

Perennial sunflowers grow best in well-drained soil with average moisture. However, many types are adapted to drought, while some, like the swamp sunflower, prefer swampy moist soil. Some perennial sunflowers do well in average to poor soil, while some like soil rich in nutrients. Be careful with the larger growing types; if planted in too-rich soil, they may flop over from an overabundance of growth.

Temperature and Humidity

Perennial sunflowers tolerate heat, drought, and high humidity. They thrive in sun and heat but can grow in slightly chilly weather as long as it is sunny.

Fertilizer

Fertilize established perennial sunflowers once a year in spring when new growth appears with a low nitrogen, granular fertilizer. (Nitrogen encourages foliage, not flowers.) Dig it into the soil 6 inches away from the plant stem, following the product directions.

Pruning

Perennial sunflowers don't require much pruning. Cut the plants back by two-thirds and remove any debris or damaged foliage in early spring.

Potting and Repotting Perennial Sunflower

Perennial sunflowers aren't ideal container plants because they don't like to be transplanted. However, the smaller varieties will grow in a sturdy, well-draining container filled with a mix of garden soil and compost. Choose a large container so the plant never needs to be repotted.

Pests and Problems

Aphids are known to frequent perennial sunflowers in spring and early summer. They can be controlled by a blast of water or applications of neem oil or insecticidal soap.

Perennial sunflowers that grow in less than full sun are likely to encounter fungal diseases.

How to Propagate Perennial Sunflower

Propagate perennial sunflower by division or seed.

Division: Perennial sunflowers have rhizomes that spread. Experienced gardeners recommend dividing perennial sunflowers every three years for the plant's health, but they can also be divided more frequently than that to produce new plants. Lift an established plant and root ball and use a sharp spade or a knife to cut away a section containing both rhizome and foliage. Plant the division in a prepared bed in the garden immediately or in pots filled with good-quality potting soil.

Seed: After the plant dies back and the blooms are dry, cut the bloom and a section of its stalk and put it in a container to catch any loose seeds. Tie a paper bag over the bloom to prevent birds from eating the seeds on the plant before they are ready for harvest. You can also cut the blooms earlier and hang them by their stalks in a warm, dry area if they need additional drying time after they are cut.

When the blooms are dry, hold them over a container and rub them with your hands to release the seeds. Rinse the seeds in a colander and remove any excess bits and pieces that aren't seeds. Spread them in a single layer on newspaper or paper towels and leave them overnight in a warm, dry place. Store them in a container until planting time.

Types of Perennial Sunflower

'Lemon Queen' Sunflower

Helianthus 'Lemon Queen' is a bold plant that reaches 4-6 feet tall. Its single, light yellow flowers are produced in abundance from midsummer to fall. Staking may be necessary if the soil is rich. Zones 5-9

'Low Down' Sunflower

Helianthus angustifolius 'Low Down' packs the flower punch of tall perennial sunflowers but only grows 18 inches tall. It requires no staking and blooms from midsummer to fall. Zones 5-9

Swamp Sunflower

Helianthus angustifolius bears masses of bright yellow daisies with brown-purple centers atop rough, 6-foot-tall stems in early fall. Zones 6-9

Willow-Leaf Sunflower

Helianthus salicifolius features delicate thin leaves on tall stems with clear yellow blooms and brown centers. It grows 8-10 feet. Zones 4-9

Perennial Sunflower Companion Plants

Dahlia

Nothing beats a dahlia for summer color. Growing these varied, spiky flowers is like having a box of garden crayons. In mid- to late summer, the flowers form on branching, fleshy stems or open in solitary splendor on bedding plants. Several different flower categories, from petite mignonettes to gigantic dinner-plate dahlias, offer possibilities for any space.

Daylily

Daylilies are so easy to grow that you'll often find them growing in ditches and fields, as escapees from gardens. Yet they look so delicate, producing glorious trumpet-shaped blooms in myriad colors. There are some 50,000 named hybrid cultivars in a range of flower sizes (the minis are very popular), forms, and plant heights. Some are fragrant. The flowers are borne on leafless stems. Although each bloom lasts only a day, superior cultivars carry numerous buds on each scape, so bloom time is long, especially if you deadhead daily. The strappy foliage may be evergreen or deciduous.

Salvia

Few gardens don't have at least one salvia growing in them. Whether you have sun or shade, a dry garden or lots of rainfall, there's an annual salvia that you'll find indispensable. All attract hummingbirds, especially the red ones, and are great picks for hot, dry sites where you want tons of color all season. Most salvias don't like cool weather, so plant them outdoors after all danger of frost has passed.

Garden Plan for Perennial Sunflower

Easy-Care Summer Garden Plan

The secret to nearly nonstop color in this easy-care summer garden plan is overlapping bloom times. The low-maintenance perennials in this design produce a palette of pink, purple, yellow, and white flowers from spring into fall, but they're at their brightest during the warmest months.