How To Start Zinnia Seeds Indoors & By Direct Sowing

Get a jump start on the growing season!

How to Start Zinnia Seeds

How to Start Zinnias Indoors and by Direct Sowing

Zinnias are some of the easiest and most rewarding flowers to grow, making them a favorite among gardeners and flower lovers. Their vibrant blooms attract pollinators and bring long-lasting color to gardens and floral arrangements. Whether you want an early start to the season by growing them indoors or prefer the simplicity of direct sowing, this guide will help you successfully grow zinnias from seed.

Starting Zinnias Indoors

Starting zinnias indoors is a great option if you want earlier blooms, live in a cooler climate, or want to ensure strong, healthy plants before transplanting them outside.


When to Start

Zinnias grow quickly, so start them 4-6 weeks before your last expected frost date. Transplant them outside only when the soil is warm and all danger of frost has passed.

Materials Needed
• Zinnia seeds (such as La Petite Zinnias, Strawberry Bon Bon, or Delectable Pastels)
• Seed-starting trays or small pots
• Seed-starting mix (light, well-draining)
• Grow lights or a sunny windowsill
• Spray bottle for misting
• Heating mat (optional, but helpful for faster germination)

Steps to Start Zinnias Indoors
1. Fill Seed Trays – Use a light, well-draining seed-starting mix in trays or small pots.
2. Sow Seeds – Plant zinnia seeds ¼ inch deep in the soil and lightly cover them.
3. Moisten the Soil – Mist the soil with a spray bottle to keep it damp but not waterlogged.
4. Provide Warmth – Keep the soil temperature around 70-75°F (21-24°C) for the best germination rate. Using a heat mat can speed up sprouting.
5. Give Them Light – Place under grow lights for 12-14 hours a day or in a sunny windowsill with at least 6 hours of direct sunlight.
6. Thin the Seedlings – Once seedlings have two sets of true leaves, thin them out so they have 2-3 inches of space to grow strong.
7. Harden Off Before Transplanting – About a week before transplanting, gradually expose seedlings to outdoor conditions to prevent transplant shock.

Direct Sowing Zinnias Outdoors

Zinnias are one of the best flowers to direct sow, as they grow quickly and don’t like being disturbed once established.

When to Direct Sow

Wait until after the last frost, when soil temperatures reach at least 70°F (21°C). Zinnias thrive in warm conditions and will sprout quickly in the right environment.

Best Location & Soil Preparation
• Choose a full-sun location (6+ hours of direct sunlight daily).
• Ensure well-draining, fertile soil with organic matter.
• Avoid overly rich soil, as it can lead to excess foliage instead of blooms.
• Rake the soil lightly to create a fine seedbed.

Steps to Direct Sow Zinnias
1. Prepare the Soil – Loosen and smooth the soil before planting.
2. Sow Seeds – Plant seeds ¼ inch deep and space them 2-4 inches apart (thin to 9-12 inches for larger varieties).
3. Water Gently – Keep the soil moist until germination, which usually takes 5-7 days in warm conditions.
4. Thin Seedlings – Once the plants are a few inches tall, thin them out to allow for airflow and prevent overcrowding.
5. Mulch & Maintain – Mulch around plants to retain moisture and suppress weeds. Water regularly, but avoid overhead watering to prevent powdery mildew.

Indoor vs. Direct Sowing: Which is Best?

Both methods work well, but if you want earlier blooms or have a short growing season, start indoors. If you prefer a simple, low-maintenance approach, direct sowing is best.

Final Tips for Growing Healthy Zinnias
• Deadhead regularly to encourage continuous blooming.
• Avoid overhead watering to prevent fungal diseases.
• Plant in succession every few weeks for blooms all season long.
• Save seeds from your favorite varieties for next year!

Whether you start your zinnias indoors or sow them directly in your garden, these vibrant flowers will reward you with months of beautiful blooms. Happy growing!

Explore Unique Zinnia Seeds

Looking for specialty zinnia varieties? Check out La Petite Zinnias, Strawberry Bon Bon, Delectable Pastels, and Moody zinnias—perfect for stunning floral displays!