Helianthus giganteus (Giant Sunflower)

Plant Info
Also known as: Tall Sunflower, Swamp Sunflower
Genus:Helianthus
Family:Asteraceae (Aster)
Life cycle:perennial
Origin:native
Habitat:sun; moist woods, marshes, swamps
Bloom season:July - September
Plant height:4 to 10 feet
MN county distribution (click map to enlarge):Minnesota county distribution map
National distribution (click map to enlarge):National distribution map

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Detailed Information

Flower: Flower shape: 7+petals

[photo of flower] Flowers are about 2 to 3 inches across, 10 to 20 petals (ray flowers). The petals are bright to golden yellow; the center is a darker yellow. There are several to many flowers branching off at the top of the plant, each at the end of a stalk less than 4 inches long.

[photo of bracts] The bracts are long, narrow, loose and hairy.

Leaves and stem: Leaf attachment: alternate Leaf attachment: opposite Leaf type: simple

[photo of leaves] Leaves are up to 7 inches long and 2 inches wide, with little or no stalk. The texture of the upper side is very rough but the underside is more softly hairy. The edges are finely to coarsely toothed. Attachment is mostly alternate, but the lower leaves may be oppositely attached.

[photo of stem] The stem is stout, covered in spreading hairs, and green or reddish purple.

Fruit: Fruit type: seed without plume

The center disk forms a head of dry seed, each about 1/8 inch long and without a tuft of hairs but with 2 bristly scales.

Notes:

Giant Sunflower is most similar to Sawtooth Sunflower (Helianthus grosseserratus), which has a hairless stem that often has a white bloom, whereas Giant Sunflower has a hairy stem and hairier leaves. Jerusalem Artichoke (Helianthus tuberosa) is also a tall sunflower, but has shorter (and usually) wider bracts and rather broader leaves.

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More photos

Photos by K. Chayka taken at Pioneer Park, Anoka County. Other photos courtesy Peter M. Dziuk.

Comments

Have you seen this plant in Minnesota, or have any other comments about it?

Posted by: Mike - Shoreview, between Lexington & Hodgson on Cty Road J
on: 2011-09-10 09:19:13

There is an artificial pond that was put in to replace wetlands taken for construction about 3/4 mile from Hodgson on CTY Rd J. They planted a full season of beautiful MN wildflowers to bloom every month. The Giant Sunflowers and Prairie Sunflowers are blooming now 9/10/2011.

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