The short answer
Too little light is a common cause of long, thin seedling stems. Check the light your seedlings actually receive before adding fertiliser.
See the sourceIn this guide
Check your situation
- Look for elongated stems and check whether the seedlings rely only on a window. The Minnesota guide identifies insufficient light as a major cause; this is a starting point, not a diagnosis of every weak seedling.
What to do now
- Review the seed packet and your lighting setup.
- If using a lamp, follow its instructions for distance and crop coverage.
- Check drainage and keep the growing mix moist during germination.
What not to do
- Do not leave lights on continuously. Avoid treating extra fertiliser as a fix for poor light.
Do you need to buy anything?
Check whether your existing lighting can be positioned appropriately. If it cannot provide enough light, review the university guide before choosing a light.
Keep going
Sources behind this page
- University of Minnesota Extension: Starting seeds indoorsMinnesota, United States. Indoor seed starting. Regional calendar dates are not universal.Source checked 7 October 2026
We summarise published guidance. We have not independently tested these methods or the products discussed.
AI-assisted editorial check: 7 October 2026. This is a source and clarity check, not a review by a horticultural expert.