The Best Vegetables to Start Indoors Early – A Complete Step-by-Step Guide

If you’re eager to get a head start on the growing season, starting vegetables indoors early is a smart strategy. By sowing seeds inside while it’s still too cold outdoors, you can grow stronger, earlier crops and enjoy bigger harvests.
In this complete guide, we’ll show you the best vegetables to start indoors, when and how to sow them, and tips for healthy seedlings that thrive when moved outside.

Why Start Vegetables Indoors?

Starting seeds indoors offers huge advantages:

• Extend the growing season: Get an earlier harvest, especially for long-season crops.
• Protect young plants: Keep seedlings safe from unpredictable weather and pests.
• Save money: Grow a wide variety of plants from inexpensive seeds.
• Increase success: Control temperature, moisture, and light for better germination.

Tip: A few basic tools — like seed trays, compost, and grow lights — are all you need to get started!

The Best Vegetables to Start Indoors Early

Not every vegetable benefits from early indoor sowing, but these ones definitely do:

Tomatoes

• When to sow: January–March
• Notes: Needs warmth and plenty of light.
• Tip: Sow early for a long growing season, but be ready to pot up seedlings before planting outside.

Peppers (Chillies and Sweet Peppers)

• When to sow: January–February
• Notes: Long-growing crops that need heat.
• Tip: Germinate seeds on a heated propagator or sunny windowsill.

Aubergines (Eggplants)

• When to sow: January–February
• Notes: Needs consistent warmth and a long season to fruit well.
• Tip: Grow under lights for best early growth.

Celery and Celeriac

• When to sow: February–March
• Notes: Slow to germinate and grow; benefit hugely from an early start.
• Tip: Sow thinly and keep moist without waterlogging.

Onions (from Seed)

• When to sow: January–February
• Notes: Starting early gives onions time to bulk up.
• Tip: Sow in trays or modules for easy transplanting.

Leeks

• When to sow: January–March
• Notes: Slow-growing and hardy.
• Tip: Start indoors then transplant outdoors from May onwards.

Brassicas (Cabbage, Cauliflower, Broccoli, Kale)

• When to sow: February–March
• Notes: Start indoors to avoid pests and get a strong early crop.
• Tip: Harden off seedlings carefully before transplanting.

Lettuce and Salad Leaves

• When to sow: February onwards
• Notes: Quick germinators perfect for early spring salads.
• Tip: Sow small amounts every few weeks for continuous harvests.

Herbs (Basil, Parsley, Coriander)

• When to sow: January–March
• Notes: Tender herbs like basil benefit from an early, warm start.
• Tip: Keep herbs near a sunny window or under grow lights.

Vegetables You Should NOT Start Indoors Too Early

Some vegetables don’t like transplanting and are best sown directly later:

• Carrots
• Parsnips
• Beetroots
• Radishes
• Turnips
• Peas (can be started indoors in modules but prefer outdoor sowing)

Tip: Always check seed packet advice — some crops resent root disturbance.

How to Start Vegetables Indoors Successfully

Equipment you’ll need:

• Seed trays, pots, or modules
• Seed compost (light, fine mix)
• Labels and markers
• Grow lights or a bright windowsill
• Heated propagator (for chillies, peppers, and aubergines)

Step-by-Step: Starting Seeds Indoors

1. Fill trays with moist seed compost.
2. Sow seeds according to packet instructions (depth and spacing).
3. Cover lightly with compost or vermiculite if needed.
4. Water gently and place somewhere warm.
5. Use grow lights if natural light is poor.
6. Keep compost moist but not soaking.
7. Prick out and pot on seedlings when they have true leaves.
8. Harden off carefully before planting outside.

When to Start Hardening Off Plants

Before moving indoor-grown plants outside, harden them off gradually.

How to harden off:

• Place plants outdoors in a sheltered spot during the day.
• Bring them back inside at night.
• Increase outdoor time over 7–10 days.

Tip: Hardening off toughens up plants against wind, sun, and cooler nights.

Common Mistakes to Avoid When Starting Seeds Indoors

• Sowing too early: Seedlings can get leggy if kept indoors too long.
• Lack of light: Poor light causes spindly, weak plants — use grow lights if needed.
• Overwatering: Damp compost invites fungal diseases like damping-off.
• Skipping hardening off: Leads to transplant shock and slow growth.

Conclusion: Start Strong with Early Indoor Sowing

Starting the best vegetables indoors early is one of the best ways to maximise your growing season and harvest success.
With the right crops, careful sowing, and good aftercare, you’ll enjoy stronger, earlier, and more productive plants when the outdoor season gets into full swing.
Get your seeds started today — and give your garden the head start it deserves!

Top 10 Questions and Answers about Starting Vegetables Indoors

1. When should I start sowing tomatoes indoors?
From late January to March, depending on your last frost date.

2. Do I need grow lights for indoor sowing?
Not always, but they help prevent leggy seedlings in low light conditions.

3. What temperature is best for germinating seeds?
Most seeds germinate best between 18–22°C (65–72°F).

4. Can I sow carrots indoors?
No, carrots dislike transplanting — sow them directly outdoors.

5. How soon after sowing do seedlings appear?
It varies — tomatoes in 7–10 days, chillies can take 2–4 weeks.

6. What’s the best compost for starting seeds?
Use a fine-textured, low-fertility seed compost.

7. Can I reuse seed trays?
Yes, but clean and disinfect them first to prevent disease.

8. When should I pot on seedlings?
When they have at least two true leaves and look crowded.

9. How much water do seedlings need?
Keep compost evenly moist but not waterlogged — little and often.

10. What happens if I sow seeds too early?
Seedlings may become leggy and weak before it’s safe to plant outdoors.