How big should seedlings be before transplanting?
Written by
Nguyen Minh
Reviewed by
Prof. Samuel Fitzgerald, Ph.D.When seedling size knowledge prevents transplant shock and aids survival success rates, if you transplant a plant too early, its roots will be weak and vulnerable. If you transplant a plant that is too big, its roots will be so large that they become root-bound within the transplant. I figured this out after losing cucumber seedlings because they were transplanted too early. True leaves and stem height are very reliable indicators of plant readiness.
True leaves do more than just show size; these secondary leaves can also indicate photosynthesis ability. It is when seedlings develop 2-3 true leaves that their root strength can be adequate to support transplantation. I find that my basil thrives when moved at this stage, rather than earlier.
Leaf Inspection
- Check for 2-3 true leaves beyond seed leaves
- Ensure leaves are deep green without spots
- Avoid seedlings with yellow or curled foliage
Root Assessment
- Gently lift seedling to check root visibility
- Healthy roots appear white and fuzzy
- Discard plants with brown or slimy roots
Different plants require different methods. Root vegetables (such as carrots) rarely transplant well since damage to the taproot will generally fail the crop. Tomatoes can be planted deeper, while peppers must be planted exactly at the same soil level. Always research the specific needs of each plant species before transplanting seedlings.
Keep a close eye on root binding. Seedlings that have become bound are often slow to grow and exhibit yellow leaves. I transplant them right away, regardless of their size. When transplanting the seedlings, tease the roots so that they can grow out into the new medium.
Read the full article: When to Transplant Seedlings: Ultimate Guide
