Illustration
Giant Sunflower
Helianthus annuus 'Mammoth Russian'
Giant Sunflower blooms from July through September.
Months here are Northern Hemisphere months; in the Southern Hemisphere, shift them by six months.
Growing Giant Sunflower
Plant it in full sun. It prefers moderate water. It is hardy in USDA zones 2–11. Expect it to reach about 8 ft tall and 2 ft wide at maturity, in roughly 1 year (not yet checked).
No toxicity note is on file for Giant Sunflower. That is not a clearance: check its safety for people and pets before planting.
What this means
Generated by an earlier AI feature of BloomsEye and not yet checked against outside sources, its scientific name included, so treat every fact above as a starting point. An audit keeps its values consistent with the rest of the library, which is not the same as being right. The source-by-source check is working through the whole library in the open, and a checked plant says so in this row.
When to plant Giant Sunflower
Wait until all danger of frost has passed, then plant out Giant Sunflower into warm soil; in most zones that means late spring. Planted then, it flowers from July to September.
Month-by-month timing for your zone is on the planting calendar; if you garden near zone 6, the middle of this plant's hardy range, start with zone 6 in April. Derived from the plant's category, zones and bloom months plus typical zone frost dates, not checked separately.
How big does Giant Sunflower get?
8 fttall5 ft 7 inan adult2 ftwideSee Giant Sunflower in a garden plan: the planner shows it in 3D beside everything else you add, growing toward this size over the years.
How far apart to plant Giant Sunflower
Derived from the mature spread above by a fixed rule, not checked separately: spacing is the spread, center to center.
Space Giant Sunflower about 2 ft apart, center to center, so each plant has room to reach its full width.
Add Giant Sunflower to a garden plan and the planner draws it at its full width, so you see the spacing before you buy.
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Design a garden with this
Drop this plant onto a 3D plan, see how it fills in, and watch your whole garden bloom across the year.