Zinnias are one of the easiest annuals to grow, grow quickly, and bloom heavily. They make a massive burst of color in your garden. Zinnias have bright, solitary, daisy-like flowerheads on a single, erect stem. The most common zinnia is "dahlia-flowered" and grows up to three feet. Other types are "cactus-flowered." Use in an annual or mixed border. Smaller zinnias are suitable for edging, window boxes or other containers. The narrow-leaf zinnia also works well in hanging baskets. Zinnias are very popular for cut flowers.
- Zinnias are grown from seed; they grow very quickly in the right conditions. Zinnias do not like to be transplanted.
- Full sun is essential wiht a minimum daylight temperature of 60 degrees F.
- Zinnias are adaptable but prefer fertile, humus-rich, well drained soil at pH preference 5.5 - 7.5.
- If soil is amended with compost, the flowers will grow more quickly.
- Sow seeds 1/4-inch deep.
- Space plants 4 to 24 inches apart depending on variety. (Many common varieties are 6 inches within the row and 2 feet in between rows.) See back of seed package.
- Germination occurs at 74 to 80 degrees F in 5 to 76 days.
- Sow in succession for a longer flowering display.
- Deadhead to prolong flowering.
- Maintain moderate soil moisture and fertilize lightly.
- Zinnias will die with the first frost.
- Bacterial and fungal spots, powdery mildew, bacterial wilt. Minimize wetting of foliage to avoid disease.
- Caterpillars, mealybugs, and spider mites also cause problems. Avoid spraying and tolerate some leaf damage unless the situation is uncontrolled.
Zinnias generally take 60 to 70 days from seed to flower (though it depends on conditions).
- Get a full-size flower on a compact plant with cultivars of the 'Dreamland Series.' Dwarf and compact, these zinnias have fully double flowerheads, to 4 inches across in a wide color range; stems are 8–12 inches tall.
- The 'Thumbelinia Series' cultivars and dwarf and spreading, with single or semi-double, weather-resistant flowerheads in many colors. Their petals are 1-1/4 inch across and stems grow up to 6 inches long.
- The 'State Fair Series' are the biggest and tallest of them all with large, double flowerheads that are 3 inches across. Stems grow to 30 inches tall.