How to Start Seeds Indoors

Why wait for spring when you can start your garden today? Indoor seed starting lets you take control of your growing season, experiment with new varieties, and enjoy the satisfaction of nurturing plants from the very beginning. With a few supplies, some patience, and a bit of guidance from Wood Country Building Services, you’ll be ready to turn tiny seeds into thriving garden favourites.

Why Start Seeds Indoors

Starting seeds indoors gives your plants a head start before outdoor temperatures are warm enough for germination. It’s invaluable in colder regions with shorter growing seasons, allowing you to grow a wider variety of plants — including those that take longer to mature, like tomatoes, peppers, and many flowering varieties.

It’s also a fascinating and rewarding process. Watching your seedlings sprout, grow, and eventually thrive in your garden connects you more deeply to your plants and helps you understand their growth cycles from the ground up.

Choosing the Right Seeds

Not all seeds benefit from being started indoors. Some, like beans, peas, and root vegetables, prefer to be sown directly into the soil outside. Focus on plants that need extra time or warmth to get established, such as:

• Tomatoes and peppers
• Eggplants
• Broccoli, cabbage, and cauliflower
• Herbs like basil, parsley, and oregano
• Annual flowers like petunias and marigolds

When selecting seeds, look at the packet for instructions on when to start them indoors. Most will list a timeline such as “Start indoors 6–8 weeks before last frost.” You can find your region’s average last frost date online or by checking with your local garden centre.

Gathering Your Supplies

You don’t need a fancy setup to start seeds indoors, but having the right tools will make a big difference. Here’s what you’ll need:

• Seed trays or small containers: These can be plastic cell trays, biodegradable pots, or even clean yogurt cups with drainage holes.
• Seed-starting mix: This lightweight, sterile soil blend provides the perfect texture and drainage for germination. Avoid using outdoor soil, which can compact and harbour pests.
• Labels: Keep track of what you’ve planted and when.
• A clear plastic cover or dome: Helps maintain humidity while seeds germinate.
• Grow lights or a bright window: Young seedlings need plenty of light to grow strong and healthy.
• A watering can or spray bottle: Use gentle watering to avoid disturbing seeds.

Preparing Your Containers

Fill your seed trays or containers with seed-starting mix, moistened slightly before use. The mix should feel damp but not soggy — like a wrung-out sponge. Gently press it into place, leaving a bit of space at the top for watering later.

If you’re reusing old containers, wash them thoroughly with warm, soapy water and rinse with a mild bleach solution (one part bleach to nine parts water) to prevent disease.

Planting Your Seeds

Each seed packet will tell you how deep to plant your seeds. As a general rule:

• Tiny seeds like lettuce or petunias should barely be covered.
• Larger seeds, like tomatoes or peppers, can be planted about 0.5 to 1 cm (¼”-½”) deep.

Place one or two seeds per cell, cover lightly with mix, and mist with water to settle them in. Label everything — it’s easy to forget what you planted once the trays fill up!

Cover the trays with plastic lids or wrap to keep moisture in and place them in a warm spot. Most seeds germinate best between 20°C and 25°C (68°F-77°F).

Providing the Right Light

Once seedlings emerge, they’ll need plenty of light to prevent them from growing tall and spindly. A sunny south-facing window can work if it provides 12–14 hours of direct light each day. If not, consider investing in grow lights.

Position the lights about 5–10 cm (2”-4”) above your seedlings and adjust as they grow. Set a timer to provide consistent light each day, and remember to turn the lights off at night so plants can rest.

Watering and Care

Keeping your seedlings evenly moist is key. The top layer of soil should never dry out completely, but it shouldn’t be waterlogged either. A fine mist spray or bottom watering (adding water to the tray below the pots) works well.

Once your seedlings develop their first set of “true leaves” — the second pair of leaves that look like the plant’s mature foliage — you can begin feeding them with a diluted, balanced liquid fertilizer every 10–14 days.

When and How to Transplant Seedlings

Before you move your seedlings outdoors, they’ll need to be “hardened off.” This means gradually exposing them to outdoor conditions to help them adjust.

Start by placing trays outside in a sheltered, shaded area for a few hours each day. Over a week or two, increase their time outdoors and exposure to sun and wind.

Once nighttime temperatures are consistently above freezing and your seedlings look strong, it’s time to transplant them into the garden. Choose a cloudy day or late afternoon to avoid transplant shock, and water them well after planting.

Troubleshooting Common Problems

Even experienced gardeners run into challenges with seed starting. Here are a few common issues and how to fix them:

• Leggy seedlings: Usually caused by insufficient light. Move seedlings closer to a light source or use grow lights.
• Mould or fungus: Caused by overwatering or poor air circulation. Let the surface dry slightly and improve ventilation.
• Seeds not germinating: Check the temperature and moisture level, and ensure seeds are still viable.
• Yellowing leaves: May indicate a need for nutrients — try a diluted fertilizer.

Advanced Tips for Experienced Gardeners

If you’re ready to level up your seed-starting game, try these pro tips:

• Use a heat mat: Keeps soil evenly warm for faster germination, especially for peppers and tomatoes.
• Transplant into larger pots: Once seedlings outgrow their starter cells, move them into slightly bigger containers to encourage strong root systems.
• Experiment with soil blocks: These eliminate plastic waste and promote healthier root growth.
• Track your progress: Keep notes on what varieties performed best, germination rates, and timing to improve each season.

Enjoy the Process

Seed starting indoors is part science, part art — and entirely satisfying. It gives you more control over your growing season and helps you connect with your plants from day one.