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Sunflowers

Quick facts 

  • The sunflower is an easy, fast-growing flower and can be a fun addition to your garden.
  • Sunflowers are not just yellow, they come in a variety of colors from pale white to deep red.
  • Sunflowers are simple to start from seed and can be planted in succession to have season-long color.
Yellow "Starburst" sunflower with bee on flower head.
'Starburst' sunflower

Sunflowers (Helianthus annuus) are an annual plant that is very popular in Minnesota gardens. Native to North America, sunflowers have been used for over a thousand years as ornamental plants and harvested for seeds, oil and dyes. 

Whether you want to grow sunflowers to add color to your garden, to use as a natural child’s playhouse or to include in bouquets and arrangements, there is a sunflower for you.

Starting sunflowers from seed

Sunflowers are one of the easiest flowers to start from seed. The seed is large and easily handled, and you can direct seed into the garden, or germinate indoors and plant in the garden once true leaves have formed. Whichever way you choose, the cultivation of the sunflower is the same.

Light 

Sunflowers enjoy full sun.

Soil

  • Sunflowers generally grow best on well-drained soils.
  • They are tolerant of clay loam or silty clay loam soils, and perform well on sandy loam soils. 
  • Sunflowers do best when grown in slightly acidic soil with a pH from 6.0 to 6.8. 
  • Prior to planting, it is best to use a soil test to determine your soil’s nutritional needs. 

Planting

Direct seeding

  • Direct seed sunflowers after all danger of frost has passed. 
  • Plant seeds one inch deep. 
    • For varieties that are 2-5 feet tall, leave about 6 inches between them. 
    • Space taller sunflowers at least 1’ apart and giant sunflowers 2’ apart. 
  • Seeds germinate within 7-10 days.

Starting sunflowers indoors

  • Sow seeds indoors in biodegradable containers. 
    • This will allow you to plant the entire pot without disturbing the seedling roots. 
    • Remove any part of the container that sticks above the soil surface as it will act like a “wick” and dry out the roots. 

Succession planting

You can have sunflowers blooming all season long through succession planting. There are three ways of doing this:

  • Plant multiple varieties that have different days to maturity all at one time.
  • Plant the same variety at one- to two-week intervals.
  • Plant multiple varieties with varying days to maturity at three- to four-week intervals.

Sunflower varieties

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Maintenance

Watering

Sunflowers can withstand some drought. Water them regularly 20 days before and after flowering to encourage root growth, which is helpful with taller sunflower varieties bearing top-heavy blooms. 

Fertilizing

A side dressing of an all-purpose slow release fertilizer applied when the sunflowers have several true leaves will speed growth and produce larger flowers. 

Weeds

Control weeds by tilling, hoeing or mulching.

How to keep your sunflowers healthy

While sunflowers are relatively easy to grow, they have a few potential pests, such as wildlife and insects.

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Robin Trott, Extension educator

Reviewed in 2020

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