Sunflower
Helianthus annuus
Asteraceae · sunflower family
- Matures
- 50–95 days
- Harvest
- Once · Annual
- Sun
- 6–8+ hrs
- Spacing
- 6–15 in
Planting window
When to sow, by microclimate — foggier blocks run a different calendar than sunnier ones.
| Jan | Feb | Mar | Apr | May | Jun | |
|---|---|---|---|---|---|---|
| Foggy | ● | ◐ | ● | |||
| Sunny | ● | ● | ◐ |
| Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|
| Foggy | ◐ | ◐ | ||||
| Sunny | ◐ |
Sunlight
How well it does at each level of direct sun per day.
Soil depth
Root room it needs — useful for sizing raised beds and containers.
Spacing
Room each plant needs — along the row and between rows — for sizing beds.
- In-row
- 6–15 in
- Between rows
- 12–18 in
Growth habit
The shape it makes in the bed and how tall it gets — what tells you whether to give it a trellis, a stake, or just room.
- Habit
- Upright
- Mature height
- 5–10 ft
Stands on its own; the tallest types appreciate a stake in wind.
How to start it
Sow it where it grows, or raise it under cover and set it out — and how far ahead to start the seedlings if it's the latter.
- Usually
- Direct-sow
Sown straight into the bed it will grow in.
Getting started
How it goes in the ground — how deep to sow or set it, and the soil temperature it needs to wake up. The cold-soil floor is the real limiter for direct-sowing in a foggy SF spring.
- Started from
- From seed
- Ideal soil temp
- 70–85°F
- Sow depth
- 0.5 in
- Time to emerge
- 7–11 days
Germinates between 50–95°F; happiest around 70–85°F.
Pests & diseases
What tends to trouble this crop — what it is, what you'll see, and what to do about it, least-toxic first.
Our sources document no specific pests or diseases for this crop; it's generally grown without major pest trouble in home gardens.
Sources
Every figure above is backed by these.
- UC Master Gardeners, San Mateo–SF Countiesbacks plantingWindow, startMethod · Foggy & Sunny calendars, Sunflower (seed) rows: Foggy sows Apr (wks 3-4) & Jun (wks 1-2); Sunny sows Apr (wks 3-4) & May (wks 1-2). Start method: Foggy & Sunny calendars, Sunflower row: (S) sow seed only.
- Golden Gate Gardening (Pam Peirce)backs plantingWindow, lifecycle, harvestStyle · Peirce Foggier/Sunnier planting-times charts, Sunflower row: Foggier Jul-Aug; Sunnier Jun-Jul. Used to extend the warm-season tail to 'maybe' and bridge the May gap. Habit and harvest: annual, once — from this source's entry for this crop.
- Utah State University Extensionbacks daysToMaturity, inRowSpacing, sunlight, rowSpacing, plantingDepth, startMethod · USU Sunflower Cut Flower Production: 'Single-stem sunflowers reach maturity in 50 to 95 days'; in-row 4-6 in (single-stem); 'Sunflowers require full sun and well-drained soil.'. Between-row spacing 12-18 in from the same USU source (single-stem rows 12-18 in apart). Planting depth 1/2 in: 'Seeds ... set 1/2-inch deep'. Start method: USU Extension sunflower: 'Harvest begins about 50 to 60 days after seeding or transplant' — transplanting is practised, but no seed-to-transplant time is published and the SF calendars sow in place.
- UGA Cooperative Extensionbacks inRowSpacing, sunlight · Growing Sunflowers in the Home Garden (C1121): sow ~6 in apart, 'thin every other seed, allowing 12 to 15 inches between plants'; 'best located in full sun.' Sets the open-garden upper bound on in-row spacing.
- UC ANR — Green Blogbacks soilDepth · UC ANR: sunflower's low water needs are attributed to its 'deep tap root' — the basis for classifying it deep-rooted.
- North Dakota State University Extensionbacks germination · NDSU Sunflower Production Guide: soil ~50°F required for germination; emergence ~10 days. UGA C1121 corroborates strong germination over the first 7–10 days. Optimal 70–85°F warm-season band.
- USDA GRIN Taxonomybacks botany
- NC State Extension — Plant Toolboxbacks growthHabit · Helianthus annuus entry: Height '1 ft. 6 in. - 10 ft. 0 in.' (18-120 in), Habit/Form 'Erect' — a single tall self-supporting stalk, so upright. The species range spans dwarf (~1.5 ft) to giant (~10 ft) cultivars; the stored 60-120 in (5-10 ft) is the common tall garden-sunflower band within that range, chosen because height varies hugely by type.