Mexican Sunflower Seeds

Directly sow Tithonia Rotundifolia seeds outside after the last frost by pressing them lightly onto the surface, not burying them deeply, just a few millimeters. Soil temperature of 65–70°F  triggers the germination process. If it is colder, they just go dormant. If conditions are favorable, Mexican Sunflower seeds sprout in 7-14 days. If you start indoors, sow seeds 4-6 weeks before last frost. Note that direct sowing will always result in stockier plants anyway. Space seedlings 18-24 inches apart, otherwise they have weak and flopping stems. Give them space and they will grow like little trees.

Full sun is non-negotiable for Tithonia Rotundifolia seeds. 6-7 hours of direct sunlight and the plants will thrive. In partial shade, they become leggy and bloom poorly.  Average to poor, well-drained soil actually suits them better than rich compost beds, which push excessive leaf growth at the expense of flowers. Water consistently until established — maybe the first 3–4 weeks. After that, they become drought tolerant and require watering once in a while. Overwatering in clay soils is the easiest way to lose these plants.

Once they're established, the main task is deadheading: remove the flowers, and the plant continues to bloom throughout the fall.  In windy areas, stake the plants when they reach 3 feet tall, as they are hollow and will snap in a summer storm if not staked. No fertilizing is necessary; in fact, if you fertilize with a high nitrogen, they'll grow tall and leafy but produce fewer flowers. Monthly watering with a balanced fertilizer is fine if you have very poor soil, but most garden soil doesn't need it. For fresh bouquets, cut them when buds are just opening.