How to Plant Mexican Sunflower: Timing, Spacing, Care & Bloom

Mexican sunflower at a glance

PlantStart indoors: 8–6 wk before last frost; Direct sow: last frost

SunFull sun; heat-tolerant once established.

SpacingTall plants — give room.

Days to bloomBloom season July–Sept. (Purdue HO-80)

-9-8-7-6-5-4-3-2-1LF+1+2+3

■ Start indoors   ■ Plant out   ■ Harvest
Weeks relative to last frost (LF). Colored weeks show when our ZIP planner schedules each step.

Updated November 4, 2026

Heat annual: tall summer color until frost. Melampodium (butter daisy) is a separate heat annual — short section below.

Sourced from university extension guides. For dates where you live, use the ZIP planting planner.

Planting timing

Wisconsin Horticulture: grow from seed “either planted directly in the garden after the last spring frost date or started indoors 6–8 weeks before the average last spring frost date for earlier bloom.” (WI Mexican sunflower) Illinois: indoor 6–8 weeks before average last frost or direct seed after last frost. (Illinois Mexican sunflower)

Melampodium (butter daisy)

Melampodium (Melampodium divaricatum) is another heat-loving annual filler — not Mexican sunflower. NC: sow after last frost, or start indoors 6 to 8 weeks before the last frost and set out after frost. (NC melampodium) Clemson: direct sow after frost; or start indoors 7 to 10 weeks prior to transplanting outdoors —.

Depth and spacing

Tall plants — give room. Shallow sow for light-requiring seed (Illinois).

Sun, soil and water

Full sun; heat-tolerant once established.