What do I do once my seeds have sprouted?

November 29, 2025 •

4 min read

Over 90% of a plant's success depends on the first few weeks after germination. So, what do I do once my seeds have sprouted? Your initial actions are critical, from providing proper light to managing moisture and eventually moving your seedlings to their new home.

Quick Summary

This guide provides crucial steps for nurturing seedlings after germination, including transitioning from humidity domes, optimizing light and water, thinning overcrowded sprouts, and preparing young plants for transplanting outdoors.

Key Points

Immediate Dome Removal: Remove the humidity dome or plastic wrap right after sprouting to prevent fungal diseases like damping off.
Intense Light is Crucial: Provide 14-16 hours of bright, direct light from a grow light to prevent seedlings from becoming long and leggy.
Switch to Bottom Watering: Once sprouted, water seedlings from the bottom to strengthen roots and avoid stem rot.
Thin to the Strongest Plant: Use scissors to snip weaker seedlings at the soil line once true leaves appear to reduce competition.
Start Diluted Fertilizing: Begin feeding with a half-strength liquid fertilizer after the first set of 'true leaves' has emerged.
Promote Airflow for Strength: A small fan can help strengthen stems and prevent diseases by providing gentle air movement.
Harden Off Before Transplanting: Gradually acclimate seedlings to outdoor conditions over 7-14 days to prevent transplant shock.
Transplant Carefully: Handle seedlings by their leaves and avoid disturbing roots when transplanting to a larger pot or the garden.

Essential First Steps After Sprouting

The moment you see that first green shoot break the soil's surface, your role shifts from germinator to nurturer. This is a fragile but exciting time for a young plant. Your first actions will set the stage for its future growth and health.

Remove the Humidity Dome and Heat Mat

The humidity dome or plastic wrap that helped keep moisture in for germination is now a liability. It traps excess moisture around the young seedling, which creates the perfect environment for 'damping off,' a fungal disease that can quickly kill a young plant. Remove the cover completely to allow for air circulation. If you used a heat mat, remove it as well, as most seeds prefer cooler temperatures for the next stage of growth.

Provide Immediate and Sufficient Light

As soon as your seeds sprout, they need intense light. Without it, they will become 'leggy,' with long, weak, and spindly stems as they stretch to find a light source. A south-facing window can work, but most indoor gardeners find supplemental light necessary. Place a grow light just a few inches above the seedlings and keep it on for 14 to 16 hours a day. Use a timer to ensure they also get a period of darkness to rest and grow properly.

Adjust Your Watering Technique

Consistent moisture is still key, but your watering method should change to prevent fungal issues. Instead of misting the surface, which can lead to damping off, switch to bottom-watering. Place the entire seedling tray into a larger, solid-bottom tray filled with a couple of inches of water. The soil will wick up the water from the bottom, hydrating the roots without getting the delicate stem and leaves wet. This also encourages roots to grow downward in search of moisture, resulting in a stronger root system.

Next Steps for Developing Seedlings

Once your seedlings have a good start, they will need more space and nutrients to continue thriving.

Thin Your Seedlings

If you planted multiple seeds per cell, you will need to thin them out once the seedlings have developed their 'true leaves.' The first pair of leaves, the cotyledons, are round and provide initial nutrients. The second set are the 'true leaves' and look like a smaller version of the mature plant's leaves. Use small scissors to snip the weaker seedlings at the soil line, leaving only the strongest plant to grow. Pulling them out can damage the roots of the keeper plant.

Introduce Fertilizer

Seed starting mix is typically sterile and nutrient-free. Once true leaves appear, it's time to introduce a gentle, half-strength liquid fertilizer. Over-fertilizing can burn delicate roots, so a diluted solution is critical. Apply the fertilizer during a regular bottom-watering session, and consider using a balanced, all-purpose water-soluble feed.

Promote Airflow

Gentle air movement helps seedlings develop stronger stems. Indoors, this can be replicated with a small, oscillating fan set to a low speed, moving across the seedlings for a few hours a day. The subtle movement causes the stems to thicken, preparing them for outdoor conditions. Good air circulation also helps prevent the fungal issues that thrive in damp, still air.

Preparing for the Outdoors

Before you can plant your seedlings in the garden, they must undergo a crucial transition phase.

Hardening Off

This process acclimates tender seedlings to the harsher outdoor elements like direct sunlight, wind, and fluctuating temperatures. Without it, your plants can suffer from transplant shock, which can stunt their growth or even kill them. Hardening off takes place over 7 to 14 days before transplanting.

Hardening Off Schedule


Day	Time Outside	Location
1-3	1-2 hours	Full Shade
4-5	3-4 hours	Part Shade
6-7	5-6 hours	Morning Sun
8-10	7-8 hours	Part Sun
11-14	All Day	Full Sun

Transplanting Seedlings

Once your seedlings are hardened off and the last frost date has passed, it's time to transplant them to their final location. Choose a cloudy day to minimize stress on the plants. Handle the seedlings gently by the leaves or root ball, never the delicate stem. Dig a hole slightly larger than the seedling's root ball, place the plant, and backfill with soil, gently firming it in place. For leggy seedlings, you can bury the stem a little deeper.

Conclusion

Caring for your seedlings after they sprout is a rewarding process that involves careful attention to light, water, and gradual acclimatization. By following these steps—removing humidity domes, providing strong light, bottom-watering, thinning, fertilizing, promoting airflow, and hardening off—you can ensure your young plants develop into strong, healthy additions to your garden. The transition from a tiny sprout to a robust plant requires patience and consistency, but the result is a thriving garden you cultivated from the very beginning.

Helpful Resources

How to Start Seeds Indoors: The Ultimate Guide

Final Checks

Monitor Daily: Keep a close eye on your seedlings for any signs of distress, pests, or disease.
Label Everything: Ensure each tray or pot is clearly labeled with the plant type to avoid confusion later.
Plan Ahead: Mark your calendar for key dates, like the last frost, to help plan your hardening off schedule effectively.

Frequently Asked Questions

Remove the humidity dome or plastic wrap as soon as the majority of your seeds have sprouted. This is crucial for preventing fungal issues like damping off caused by excess moisture.

Seedlings require 14-16 hours of strong, direct light per day once they emerge. This is best achieved with a grow light placed a few inches above the plants to prevent them from becoming leggy.

The best method is bottom-watering. Place the tray in a larger container with an inch or two of water. The soil will soak up the moisture, hydrating the roots without getting the delicate foliage wet and risking fungal disease.

Wait until your seedlings have developed their 'true leaves' (the second set of leaves) before introducing fertilizer. Use a very gentle, half-strength liquid fertilizer to avoid burning the roots.

Use a small pair of scissors to snip the weaker seedlings at the soil level, leaving the strongest plant in place. Do not pull them, as this can damage the root system of the seedling you want to keep.

Hardening off is the process of gradually acclimating your indoor-grown seedlings to outdoor conditions like wind, sun, and temperature. It's essential to prevent transplant shock and ensure the plants survive when moved outdoors.

Leggy seedlings are caused by insufficient light. To prevent this, provide a strong, direct light source immediately after sprouting. Place your grow light just a few inches above the seedlings to provide the necessary intensity.

You can 'pot up' seedlings to larger containers when roots start appearing out of the drainage holes. Transplant them to the garden after they have been properly hardened off and all danger of frost has passed.