Zinnias are one of the easiest annuals to grow from seeds started indoors or direct sown in the garden. The colorful blooms attract pollinators like bees and beneficial insects. They also make long-lived flowers in bouquets and arrangements. Knowing when to plant zinnias can mean the difference between months of beautiful blooms or a short show at the of the growing season. For the best display of flowers you need to plant zinnias at the right time. Below I’ll walk you through all the steps of when to plant zinnias.

Timing considerations for when to plant zinnias

There are various factors that influence when to plant zinnias. These include soil and the average last frost date, the days to maturity for the varieties you wish to grow, and whether you’re direct sowing seeds outdoors or giving them a head start indoors. There are dozens of varieties of zinnias to choose from with flowers in a wide range of sizes, shapes, and colors. Some zinnias have single flowers with a single row of petals while others have semi-double or fully double blooms. Some even have flowers that look like buttons! Common blossom colors include red, pink, white, purple, yellow, orange, and green, as well as many bi-colors. When buying zinnia seeds be sure to read the information listed on the seed packet to learn about the days to for that specific variety.

No matter when you plant zinnias keep in mind they grow best in a garden bed or container that receives plenty of light. Look for a site with full sun and fertile, well-drained soil. Before I direct sow seeds or transplant seedlings, I amend the planting bed with compost and an organic flower fertilizer.

options for when to plant zinnias

When it comes to timing, you have a few choices for when to plant zinnias.

  1. Early to mid-spring – Sow zinnia seeds indoors under grow lights or in a sunny window.
  2. Late spring – Direct sow seeds or transplant seedlings into the garden.
  3. Late spring through early summer – Succession planting seeds or seedlings ensures months of zinnia flowers.

How to sow zinnia seeds indoors

Fill pots or cell packs with the pre-moistened potting mix. Peat pots are often recommended for starting zinnia seeds because they’re said to transplant easily into the garden. However, I don’t find peat pots down in my climate and if any part of the pot is above the soil, it wicks water away from the root system.

Plant the seeds a scant quarter inch deep and water after sowing to ensure good soil-seed contact. Move the containers to a sunny window or place them beneath a grow light. I prefer using a grow light as it produces strong, stocky seedlings. Leave the light on for 16 hours each day, using a timer to turn it on and off. Bottom water seedlings or use a watering can with a rose attachment. As the seedlings grow, feed them every 3 weeks with a fertilizer mixed at half strength. Harden off the seedlings about a week before you plan on moving them to the garden by slowly acclimatizing them to outdoor growing conditions.

When to plant zinnias: 3 options for months of beautiful blooms

Zinnias are one of the easiest annuals to grow from seeds started indoors or direct sown in the garden. The colorful blooms attract pollinators like bees and beneficial insects. They also make long-lived flowers in bouquets and arrangements. Knowing when to plant zinnias can mean the difference between months of beautiful blooms or a short show at the of the growing season. For the best display of flowers you need to plant zinnias at the right time. Below I’ll walk you through all the steps of when to plant zinnias.

Option 1 – Early to mid-spring: When to plant zinnia seeds indoors

Starting zinnia seeds indoors is an easy way to get a head start on the flowering season. That said, it’s important to sow zinnias seeds indoors at the right time. If started too early, the plants become rootbound and won’t transplant well. Zinnia seeds should be started indoors 4 to 6 weeks before the last frost date in spring.

When the time is right, gather your seed-starting supplies. Here’s what you’ll need:

  • Pots or cell packs and seeding trays
  • Seed-starting growing mix
  • Plant labels and a waterproof marker
  • Grow lights (or a sunny windowsill)
  • Watering can

Option 2 – Late spring: Direct sow zinnia seeds or transplant seedlings

It’s important to get the timing right when direct sowing seeds or transplanting seedlings outdoors. If you plant zinnias too early in spring, frost or cold can the plants. Sowing seeds in cold, wet soil can the seeds to rot. Let the weather be your guide. Sow seeds or transplant young plants after the frost and when the soil have warmed.

Option 3 – Succession plant zinnias from late spring through early summer

Zinnias are considered and come again’ flowers because they produce blooms over a long period of time. That said, after the first month of flowering, new bud production slows and you’ll get fewer blooms. To ensure months and months of gorgeous flowers, I succession plant zinnias three times. Here’s my zinnia planting schedule which is based on my average last frost date.