All About Zinnias

Can I Grow Zinnias?

Zinnias are recommended for beginning gardeners.
Zinnias are undemanding annuals that simply need full sun, warmth, and well-drained soil rich in organic matter. If soil is poor, incorporate lots of compost or leaf mold. Zinnias can be direct sown or transplanted into the garden. Space taller varieties about 12 to 18 inches apart. Space shorter growing varieties about 6 to 8 inches apart.

What is the History of Zinnias?

Zinnias are named after Johann Gottfried Zinn (1727-1759), a German professor of botany who grew the plant after it was "discovered" in the New World and brought back to Europe. Zinnias are native to Mexico, Central America, and the southwestern United States.

Should I Grow Zinnia Seeds Or Plants?

Zinnias can be direct sown or transplanted into the garden. In warmer areas with long growing seasons, sow zinnia seeds directly into the garden after all danger of frost has passed. Sow into well-prepared soil free of large clumps. Lightly cover seeds with 1/4 inch of soil since zinnia seeds need light to germinate. Keep soil moist until plants are established.

In colder regions with shorter growing seasons, sow seeds indoors about 4 to 5 weeks before the last average frost. Make sure soil temperature is kept at 70 to 80 degrees F. for good germination. Use a high quality seed starting soil mixture. Don't use garden soil as it's usually too heavy and can cause disease problems indoors.

Zinnias don't like being transplanted. Sow seeds in peat pots that can be directly transplanted into the garden. Place zinnia seeds on soil surface and lightly press into the surface. Cover with 1/4 inch of soil. Lightly water and cover with clear plastic or glass to keep seeds from drying out. Seeds should germinate in 4 to 7 days. Once up, remove cover and keep soil evenly moist.

How Do I Cultivate Zinnas?

After indoor seeds have germinated and reached 1 inch in height, thin out zinnia seedlings so remaining seedlings are 2 inches apart. For outdoor sowings, wait until seedlings are about 2 to 3 inches in height before thinning, then thin to 6-8 inches apart for smaller zinnia varieties and 12 inches apart for varieties that grow to 2 feet or more. When thinning, gently pluck up seedlings or cut them off with a scissors at soil level so the remaining seedlings' tender root systems aren't disturbed.

When zinnia seedlings reach about 4 inches tall (indoors or outdoors), give plants a quarter strength application of a 5-10-5 liquid fertilizer.

Zinnias like to be well watered especially when young; but do not like waterlogged soil. As a rule of thumb, plants like about 1 inch of water per week.

Zinnia Growing Tips

  • To have bushier-shaped zinnia plants, pinch off an inch or so from the tips of the main stems while plants are still young.
  • Regularly deadhead or remove old flowers to keep plants attractive and encourage more blooms.
  • If taller zinnia varieties begin to flop, stake with y-shaped branches or metal hoop staking around the plants.
  • A second application of a 5-10-5 fertilizer in mid season will help to keep zinnia plants growing strongly.

What Insects & Diseases Affect Zinnia?

Zinnias have no major insect problems, but are susceptible to mildew, which causes foliage to discolor and plants to lose vigor and sometimes wilt.
Mildew problems are caused by wet and/or high humid conditions. Minimize mildew problems by not over watering zinnia plants, planting in well-drained soil, and watering plants at soil level to avoid wetting foliage. Also avoid overcrowding plantings, which decreases air circulation around zinnias.

Breakthroughs in breeding have introduced excellent mildew resistance in many varieties; thus mitigating mildew problems traditionally associated with zinnias.

Zinnia Harvest Tips

When harvesting zinnia flowers for arrangements, cut stems to desired size making sure to cut just above a leaf node or bud to encourage new blooms on the remaining stem.

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