Starting Seeds Indoors: A Step-by-Step Guide

Starting seeds indoors is a rewarding way to get a jump-start on your garden, especially in Colorado with its short growing season. With the right supplies and a little know-how, you can successfully grow healthy seedlings that will later thrive in your garden. Here’s a step-by-step guide to help you get started:

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Supplies Needed:

  • Potting Soil: Choose a starter potting soil made specifically for starting seeds to ensure germination and provide a strong foundation for your seedlings.
  • Containers: Seed trays with cells that are 2-3 inches wide and deep are ideal for starting seeds. You can also use biodegradable seed cups or household items like Dixie cups or egg cartons.
  • Variety of Seeds: Choose vegetables and flowers that you will enjoy and are suitable for how much sun your garden gets. For our family, we choose to start these seeds indoors: bell peppers, cucumbers, zucchini, jalapenos, serrano peppers, spaghetti squash, and tomatoes.
  • Seed Covers: Plastic domes/lids or plastic wrap can help hold moisture and heat to facilitate germination.
  • Watering Can: Seedlings need consistent moisture, so check soil moisture daily and water as needed. Avoid flooding the seedlings. 
  • Fertilizer: Hold off on using fertilizers until later in the growth process. Organic compost can provide nutrients for the soil.

How to Start and Care for Seedlings

Starting your seeds indoors at the correct time is crucial. This website will give you a good idea of when to start your vegetable seeds indoors. 

Step 1: Choose Your Seeds 

Select seeds based on what you want to grow and the timing of your planting. Some plants, like tomatoes and peppers, need a longer growing season and are best started indoors. Others, like lettuce and radishes, can be started indoors or directly sown into the garden.

Step 2: Prepare Your Containers 

Fill seed starting trays or containers with seed starting mix, leaving a little space at the top for watering. Moisten the mix before planting to ensure it’s evenly moist but not soggy.

Step 3: Plant Your Seeds 

Follow the planting instructions on the seed packet for the correct depth and spacing. Plant 2-3 seeds per cell or container to ensure germination. After planting, lightly press the seeds into the soil and water gently.

Step 4: Provide Proper Care 

Place your trays or containers in a warm, sunny location or under grow lights. Most seeds require temperatures of 65-75°F (18-24°C) to germinate. Use a heat mat if necessary to maintain the proper temperature.

Step 5: Water Regularly 

Keep the soil evenly moist but not waterlogged. Use a watering can or spray bottle to water gently, so you don’t disturb the seeds. Check the moisture level regularly, especially as the seeds germinate and grow.

Step 6: Maintain Humidity 

Cover the trays or containers with plastic wrap or a humidity dome to help retain moisture and create a greenhouse effect. Remove the cover once the seeds have germinated.

Step 7: Provide Adequate Light 

Once the seeds have germinated, place them under grow lights or in a sunny windowsill. Seedlings need 12-16 hours of light per day to grow strong and healthy.

Step 8: Thin Seedlings 

If multiple seeds germinate in the same cell or container, thin them out by snipping off the weaker seedlings at soil level. This allows the remaining seedling to grow stronger.

Step 9: Harden Off Seedlings 

About a week before transplanting your seedlings into the garden, begin hardening them off by gradually exposing them to outdoor conditions. This process helps acclimate the plants to lower temperatures and wind, reducing the risk of shock. Start with a few hours of sunlight and gradually increase the time and exposure.

Step 10: Transplant Seedlings 

Once your seedlings are hardened off, transplant them into your garden. Choose a cloudy day or transplant in the evening to minimize stress on the plants. Water them well after transplanting to help them settle into their new home.

By following these steps, you can successfully start seeds indoors and enjoy a bountiful garden later in the season. Happy gardening!


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