Urban Farmer Learning Center
Seed Starting, Made Simple
Build strong starts for vegetables, herbs, and flowers. Choose the right method, work backward from frost, and give every seed the light, moisture, and space it needs.
Start with the decision
Inside, outside, or either?
Start indoors when a crop needs a longer season or careful warmth. Direct sow crops that dislike root disturbance, grow quickly, or germinate best in garden soil.
Start indoors
Tomatoes, peppers, eggplant, celery, and many slow flowers and herbs benefit from a protected head start.
Direct sow
Beans, peas, carrots, radishes, sunflowers, and other fast or root-sensitive crops are usually best sown in place.
Flexible crops
Lettuce, kale, cucumbers, squash, basil, and many flowers can work either way depending on season and space.
Packet wins
Use this guide for planning, then let the seed packet and crop guide override averages for a specific variety.
Interactive timing tool
Work backward from your last frost
Select a crop and your average spring frost date to estimate an indoor sowing window and planting target.
Your seed-starting plan
Choose a date to calculate
Your customized sowing window will appear here.
Weather and varieties differ. Confirm timing and depth on the packet before sowing.
Quick crop finder
Find the right starting method
Search common vegetables, herbs, and flowers. Timing is shown in weeks before the average last spring frost.
From packet to seedling
The seed-starting workflow
Label first
Write crop, variety, and sow date before seed touches mix. Group crops with similar heat and timing needs.
Moisten the mix
Use clean seed-starting mix. Add water until evenly damp, fill cells loosely, and gently level without packing hard.
Plant at the right depth
As a rule, cover seed about two to three times its width. Press light-germinating seed onto the surface.
Warm and evenly moist
Use a dome only until seedlings emerge. Bottom heat helps warmth-loving crops; remove heat after germination.
Bright light, close by
Provide 14 to 16 hours of strong light daily, usually a few inches above seedlings, adjusting as they grow.
Moist, never soggy
Check daily and bottom-water when possible. Allow airflow and slight surface drying to discourage disease.
Thin and pot up
Keep the strongest seedling per cell. Move crowded or fast-growing plants to larger containers before roots bind.
Harden off
Over 7 to 10 days, gradually increase outdoor light, wind, and time before transplanting into prepared soil.
One system, three departments
Adjust the plan for what you grow
Vegetables
- Give peppers, tomatoes, eggplant, celery, and brassicas an indoor head start.
- Direct sow most roots, peas, beans, and corn.
- Avoid starting cucurbits too early; young transplants establish best.
Herbs
- Begin slow herbs such as rosemary, lavender, and parsley early.
- Basil grows quickly and prefers warmth.
- Cilantro and dill often perform best direct sown to reduce root disturbance.
Flowers
- Start slow annuals early; direct sow quick warm-season flowers after frost.
- Check whether a variety needs light, darkness, chilling, or scarification.
- Handle taprooted flowers gently or sow them in place.
A safer transition
Harden seedlings off in stages
Begin after plants are sturdy and conditions are appropriate. Pause during frost, high wind, or severe weather.
Days 1-2
Place outdoors for 1 to 2 hours in bright shade, protected from wind.
Days 3-4
Increase to 3 to 4 hours and introduce gentle morning sun.
Days 5-6
Extend outdoor time and sun exposure. Watch moisture closely.
Days 7-10
Leave out most of the day, then transplant on a mild, cloudy day when possible.
Diagnose early
Common seedling problems
Seeds are not germinating
Check crop temperature, seed age, sowing depth, and moisture. Mix should stay evenly damp, not saturated. Some flowers and herbs need light, darkness, chilling, or extra time.
Seedlings are tall and leggy
Increase light intensity, move lights closer without overheating plants, provide gentle airflow, and avoid excess warmth after emergence.
Stems collapse at the soil line
This often points to damping off. Improve sanitation and airflow, reduce saturation, remove affected plants, and avoid reusing contaminated mix.
Leaves look yellow or purple
First check wet roots, cold mix, and inadequate light. Once true leaves form, use a weak balanced fertilizer if the mix contains little nutrition.
Roots circle the container
Pot up or transplant promptly. Tease apart only when needed, keep roots moist, and protect newly moved plants from intense sun and wind.
Seedlings wilt after transplanting
Harden off longer, transplant in mild weather, water the root zone thoroughly, and temporarily shelter plants from afternoon sun or strong wind.
Keep planning
Useful Urban Farmer resources
Ready to grow?