Winter in Indianapolis can feel long and gray, but it’s the perfect time to get a jumpstart on a colorful spring garden. By starting flower seeds indoors now, you’ll enjoy strong, healthy blooms as soon as the weather warms. Here are the top five flowers to grow indoors this winter for a spectacular spring garden.

1. Marigolds – Sunny, Hardy, and Easy

Marigolds are a classic favorite for beginner and experienced gardeners alike. Starting them indoors in late winter ensures strong, vibrant flowers ready to brighten your garden in spring.

Tips for success:

• Sow seeds in late February to early March in seed trays or small pots.
• Keep soil moist and provide plenty of light.
• Transplant outdoors after the last frost (typically mid- to late April in Indianapolis).

Marigolds are also great companions for vegetables, helping repel pests naturally.

2. Petunias – Colorful and Long-Blooming

Petunias bring vibrant, trailing blooms that are perfect for garden beds, containers, or hanging baskets. They respond well to indoor starting, giving you an early advantage over direct sowing.

Tips for success:

• Start seeds 8–10 weeks before your intended transplant date.
• Use a well-draining seed mix and keep soil evenly moist.
• Provide bright, indirect sunlight or a grow light for at least 12–14 hours per day.
• Harden off seedlings gradually before planting outdoors.

Petunias thrive in full sun once planted and will continue flowering through the summer.

3. Snapdragons – Elegant and Versatile

Snapdragons add height and structure to your spring garden with their tall, colorful spikes. Starting them indoors ensures early blooms and strong plants ready to withstand cool spring temperatures.

Tips for success:

• Sow seeds indoors in late winter, as they germinate best in cooler conditions (60–65°F).
• Press seeds lightly into the soil without covering them too deeply.
• Keep the soil lightly moist and provide bright light.
• Transplant seedlings outdoors after frost danger has passed.

Snapdragons are perfect for borders, mixed beds, and cut flowers.

4. Zinnias – Bold, Bright, and Easy to Grow

Zinnias are fast-growing, cheerful annuals that add bright pops of color to any garden. Starting them indoors can give you a head start on the season, especially in Indianapolis where spring planting can be delayed by cold weather.

Tips for success:

• Start seeds 4–6 weeks before the last frost.
• Plant in seed-starting mix and keep soil moist.
• Provide at least 12 hours of light daily for strong seedlings.
• Transplant outdoors once soil warms and nighttime temps are consistently above 50°F.

Zinnias thrive in sunny spots and attract pollinators like bees and butterflies.

5. Cosmos – Delicate, Airy Blooms

Cosmos produce beautiful, daisy-like flowers with airy foliage that add elegance to gardens. Indoor starting gives these tender annuals the extra time they need to mature before planting outdoors.

Tips for success:

• Start seeds indoors 6–8 weeks before the last frost.
• Use light, well-draining soil and keep seedlings moderately moist.
• Provide bright light to avoid leggy growth.
• Transplant outdoors once temperatures are warm and soil is workable.

Cosmos are low-maintenance, drought-tolerant, and perfect for naturalistic flower beds.

Indoor Flower Seed-Starting Tips for Indianapolis Gardeners

• Use a quality seed-starting mix and containers with drainage.
• Provide plenty of light—windows may work, but grow lights ensure stronger seedlings.
• Keep soil consistently moist but not soggy.
• Label seeds with plant name and sowing date.
• Harden off seedlings by gradually exposing them to outdoor conditions over a week.
• Check your local last frost date (mid- to late April) to time your transplanting perfectly.

Starting flower seeds indoors is a fun way to bring early color and excitement to your spring garden. With marigolds, petunias, snapdragons, zinnias, and cosmos, your Indianapolis garden will be bursting with life as soon as spring arrives.