Helianthus Plant Growing & Care Guide for Gardeners

Article by Dean Ravenscroft, Ph.D. - Updated 19th Oct 2023

In this Gardener's HQ guide, we'll explore cultivating Helianthus plants in your garden, indoor spaces, and other settings.

Sunflower, Jerusalem Artichoke, & Sunroot: Cultivation & Garden Use

Helianthus are a large genus of plants that can be grown as Hardy perennials or Hardy annuals.

They are better known as sunflowers, and both sunflower oils and sunflower seeds are of great commercial and health value.

Most people associate Helianthus plant members with great height (between 5 to 10 feet; 1.5 to 3 m), but some dwarf varieties do exist, these only reach about 18 inches (45 cm) in height.

They carry large daisy like flowers, mainly of Yellow or orange, but sometimes cream. These flowers bloom from the middle of summer until the middle of autumn.

Helianthus annuus – Annual Sunflower by TANAKA Juuyoh; creative commons.

Helianthus Plants are great to show off individually, and they can also be used as tall plants at the back of borders.

Helianthus tuberosus - Jerusalem artichoke by Blumenbiene; creative commons.

How to Grow Sunflower (Helianthus) Plants

If growing Helianthus outside, then it is best to sow the sunflower seeds outdoors at a depth of 1/4 inch (6 mm). Sow following the last frost of spring.

Sunflowers like to grow in a sunny or partially shaded area that has good drainage.

They can be grown in most soils, but if you want to grow big sunflowers then use a soil that is of pH5 to 7, deep, and rich.

You can start to grow sunflowers indoors first. When planting sunflower seed indoors, sow them in peat pots about three weeks before the last frost of spring.

They should take about 10 days to germinate, at a temperature of 70 to 86°F (21 to 30°C). Sunflower seedlings should then be transplanted with a spacing of about 40 inches (1 m), following the last frost of spring.

Caring for Sunflowers and other Helianthus in the Garden

Sunflower care is pretty easy. If you want to create bushy sunflowers, then they should be pinched back when they are young to encourage branching.

Due to their large heights, it is important to stake sunflowers to protect them from windy conditions, especially if growing as a solitary plant.

Helianthus plants require lots of watering, but only feed them lightly to produce healthier flowers.

Although sunflowers are pretty easy to look after, it is difficult to grow other plants around them. This is because they carry toxins in their roots, these act to give sunflowers a competitive advantage over other plants.

Harvesting Sunflower Seeds

If you want to use your sunflower seeds for culinary use, then they will need to be protected from birds during seed maturation. This can be done by placing a linen or cheese cloth over the head of the sunflower.

Commonly Grown Helianthus Species Photographs and Plant Identification

Helianthus annuus

Helianthus annuus (Common Sunflower), photograph by Christian Schirner; CC.

Helianthus angustifolius

Helianthus angustifolius (Narrowleaf Sunflower / Swamp Sunflower), photograph by USGS Bee Inventory and Monitoring Lab; CC.

Helianthus giganteus

Helianthus giganteus (Giant Sunflower / Tall Sunflower), picture by Mustang Joe; Public Domain.

Common Questions

How many members does the Helianthus genus have?

The Helianthus genus is diverse and has about 70 species, including the popular sunflowers.

Do members of Helianthus make a good garden or landscaping plant?

Yes, Helianthus species are prized for their vibrant, large blooms, especially the Sunflower, making them great additions to gardens or landscapes.

Which Helianthus species are most frequently grown by gardeners?

The Helianthus annuus, commonly known as the Sunflower, is a favorite for its large, bright yellow flowers.

Are members of the Helianthus plant genus fragrant?

Most Helianthus species are not notably fragrant, but their visual appeal makes up for the lack of scent.

What is the perfect location to grow Helianthus?

Helianthus plants love full sun and well-drained soil, making them ideal for sunny spots in the garden.

Is Helianthus invasive in the USA, if so in which states?

Currently, most Helianthus species are not considered invasive in the USA, although some can be aggressive self-seeders.

How do I remove Helianthus plants from my garden?

To remove Helianthus plants, pull them up from the root and dispose of them properly.

Summary

The Helianthus genus is a member of the Asteraceae family, and is best known for containing the Sunflower. Native to North America, these plants are celebrated for their large, sun-facing blooms and edible seeds.

Helianthus plants prefer a location with full sun and well-drained soil. These plants are fairly drought-tolerant, but perform best with regular watering. Sunflowers are often grown from seeds, these should be sown directly into the garden after any threat of frost has passed in late spring to early summer.

I hope that you enjoyed this guide on how to grow Helianthus plants. You may also enjoy the following Gardener's HQ growing guides: How to grow Golden Rod, Sun lovers, Helianthemum nummularium, and Cotula plants.