When and How to Fertilize Young Seedlings for Strong Growth

Starting seeds indoors gives your garden a head start, but knowing when to begin fertilizing seedlings is crucial for healthy development. The key is waiting until seedlings have established their first true leaves.

Identifying the Right Time

Seedlings initially produce cotyledons (seed leaves), which are part of the seed embryo. Wait until the first set of true leaves appears—these resemble the mature plant's foliage. At this stage, the seedling's root system can absorb nutrients effectively.

Fertilizer Schedule and Strength

• First feeding: Apply half-strength balanced fertilizer (12-12-12) or fish emulsion every 10–14 days.
• After transplanting: Once seedlings are pricked out into individual cells and show vigorous growth, switch to full-strength fertilizer every 10–14 days.

Practical Tips

Always ensure the growing medium is moist before fertilizing to prevent root burn. Use a water-soluble formula for even distribution. Monitor seedlings for signs of over-fertilization, such as leaf tip burn or excessive leggy growth.

Advice from Tom, based on decades of seed-starting experience.