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Starting Seeds Indoors

Get a head start on the growing season by starting seeds indoors weeks before the last frost.

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In This Guide

1.Why Start Seeds Indoors?

Starting seeds indoors gives you a 6-8 week head start on the growing season. This is essential for warm-season crops like tomatoes and peppers in shorter growing seasons, and it lets you have transplants ready as soon as the soil warms up.

For LocalRoots sellers, this means earlier harvests when fresh local produce commands premium prices. Those first tomatoes of summer always sell fast!

You'll also save money compared to buying transplants, have access to more varieties than nurseries stock, and know exactly how your plants were grown from day one.

2.When to Start

Use your last frost date as the anchor for all seed starting calculations. Check your LocalRoots Growing Profile for your estimated frost dates.

8-10 weeks before last frost: Onions, leeks, celery 6-8 weeks before last frost: Tomatoes, peppers, eggplant 4-6 weeks before last frost: Broccoli, cabbage, cauliflower 2-4 weeks before last frost: Squash, melons, cucumbers

Starting too early is a common mistake. Leggy, overgrown seedlings are harder to transplant successfully than younger, stockier plants.

3.Equipment Needed

Seed Starting Mix: Use a sterile, soilless mix designed for seeds. Regular garden soil is too heavy and may contain pathogens.

Containers: Cell trays, peat pots, or recycled yogurt cups with drainage holes. Start small (2-3 inch) and pot up later.

Light: A sunny south-facing window can work, but grow lights produce sturdier seedlings. LED shop lights positioned 2-3 inches above plants work great.

Heat Mat (optional but helpful): Keeps soil at optimal 70-80°F for germination. Essential for peppers and tomatoes.

Labels: Trust us - you will not remember which variety is which after a week.

4.Sowing Seeds

  1. Moisten your seed starting mix before filling containers. It should feel like a wrung-out sponge.
  1. Fill containers loosely and tap to settle. Don't pack the mix down.
  1. Create small depressions for seeds. General rule: plant seeds 2-3 times as deep as they are wide.
  1. Cover lightly with mix and mist gently.
  1. Cover with humidity dome or plastic wrap until seeds germinate.
  1. Place on heat mat if using, and check moisture daily.

Most vegetable seeds germinate in 5-14 days. Once you see green, remove any covers and get them under lights immediately.

5.Growing Strong Seedlings

Light: Seedlings need 14-16 hours of light daily. Keep lights 2-4 inches above plants and raise as they grow. Leggy seedlings are reaching for inadequate light.

Water: Keep soil consistently moist but not waterlogged. Water from below when possible to prevent damping off (a fungal disease that kills seedlings).

Air Circulation: A small fan on low prevents disease and strengthens stems.

Fertilizer: Start feeding with diluted (1/4 strength) liquid fertilizer once true leaves appear. True leaves are the second set - the first leaves (cotyledons) are seed leaves.

Potting Up: When seedlings have 2-3 sets of true leaves, move them to larger pots if roots are crowded.

6.Hardening Off

This critical step toughens up indoor seedlings before transplanting. Skip it and your plants may die from shock.

Week 1: Place seedlings outside in a sheltered, shaded spot for 1-2 hours. Bring inside.

Week 2: Gradually increase outdoor time to 4-6 hours. Introduce some direct sun.

Week 3: Leave outside all day, bringing in only if frost threatens. By week's end, they can stay out overnight.

Start hardening off 2-3 weeks before your planned transplant date. This is also when you should stop fertilizing to slow growth.

Materials & Supplies
  • Seed starting mix
  • Cell trays or small containers
  • Grow lights or sunny window
  • Spray bottle for misting
  • Plant labels and marker
  • Heat mat (optional)
  • Humidity dome or plastic wrap
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Ready to put this into practice?

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