Sunflower

Basic Information

Seed Number

63

Seed Name

Sunflower

Variety

Mammoth

Category

Flower

Plant Family

Asteraceae

Plant Type

Giant annual sunflower (Helianthus annuus)

Planting Method

Direct Sow

Seed Status

In Seed Bank

Created

2026-08-14 00:50:34

Updated

2026-08-19 15:35:29

Planting Information

Start Planting Date

May 6

Last Recommended Planting Date

Jun 30

Plantable Months

May, June

Indoor Start

Not recorded

Direct Sow

May 6 – Jun 30

Transplant

Not Recommended

Indoor Start Weeks Before Frost

Not Recommended

Transplant Weeks After Frost

Not Recommended

Germination Days

7–10 days

Harvest/Maturity

Not recorded

Succession Planting

Not recorded

Growing Conditions

Ideal Soil Temperature

60°F+

Planting Depth

1 in

Plant Spacing

24 in

Row Spacing

30-36 in

Thin-To Spacing

24 in

Sun Requirements

Full sun; 6-8+ hours/day

Water Needs

Water deeply during establishment, flowering and seed fill; established plants tolerate moderate dry periods

Soil Preference

Well-drained soil; pH approximately 6.0-6.8; adequate fertility supports maximum height and head size

Minimum Container Size

giants need ground/large pots

Plant Height

9-12 ft

Perennial/Biennial Status

Annual

Container Friendly

No

Trellis/Support Needed

No

Frost Tolerant

No

Heat Tolerant

Yes

Drought Tolerant

Yes

Pollinator Friendly

Yes

Medicinal

No

Garden Uses

Companion Planting

Storage

Seed Source/Brand

MSU Extension; Detroit frost dates; Almanac Detroit

Packet Year

Not recorded

Quantity Notes

Not recorded

Purchase Date

Not recorded

Expiration Year

Not recorded

Storage Box

Not recorded

Container

Not recorded

Envelope

Not recorded

Row

Not recorded

Slot

Not recorded

Storage Notes

Not recorded

Notes

Original Planting Method: Direct sow
Outdoor / Direct Sow / Transplant Window: May 10 – Jul 10
Days to Harvest / Bloom: 60–100 days to bloom
Container Friendly: Dwarf yes; giants need ground/large pots
Medicinal / Herbal Use: Seeds useful; pollinator support
Succession / Reusable Notes: Succession sow for blooms. Tall types need wind protection.
Zone 6B Notes: Direct sow after frost.
Companion Plants: Cucumbers, squash, pumpkins, melons, corn, pollinator flowers, clover
Avoid Planting Near / Watch Outs: Potatoes; may shade small crops
Sources: MSU Extension: https://www.canr.msu.edu/resources/garden_planning_calendar | Detroit frost dates: https://www.ufseeds.com/vegetable-planting-calendar-detroit-michigan.html | Almanac Detroit: https://www.almanac.com/gardening/planting-calendar/MI/Detroit

[[RESEARCH ENRICHMENT START]]
Zone 6B: Direct sow after the May 5 frost date when soil reaches at least about 60°F. Plant early enough for the giant seed heads to mature before the October 15 frost.
Germination: Plant about 1 inch deep. Seed usually germinates in 7-10 days under warm, moist conditions.
Harvest: Allow seed heads to mature until the back of the head yellows or browns and seeds become fully developed. Seeds can be harvested for roasting or wildlife.
Seed Saving: Allow selected heads to mature completely. Isolate from other annual sunflower varieties if true-to-type seed is important.
Special Care: Large mature heads make plants top-heavy. A wind-protected site is helpful even though Mammoth generally develops a sturdy stalk.
Research Source: Burpee — https://www.burpee.com/sunflower-mammoth-prod000397.html — Mammoth heirloom identity, 9-12 foot height, giant heads, edible seed and pollinator value
Research Source: Ferry-Morse — https://ferrymorse.com/products/organic-sunflower-mammoth — Helianthus annuus identity, giant flower heads, edible roasting seed and pollinator value
Research Source: University of Minnesota Extension — https://extension.umn.edu/gardening-minnesota/sunflowers — germination, planting depth, giant sunflower spacing, soil and direct-sowing timing
[[RESEARCH ENRICHMENT END]]