Help with indoor starts - Ask Extension
I am having some trouble when I start indoor seedlings. The leaves turn yellow and fall off, or they turn very dark. Sometimes they will be root bou...
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Help with indoor starts #904420
Asked June 05, 2025, 9:32 AM EDT
I am having some trouble when I start indoor seedlings. The leaves turn yellow and fall off, or they turn very dark. Sometimes they will be root bound, sometimes they barely have any roots at all. I use commercially prepared seed starting mix. I try to keep the soil moist until they germinate, and then I use a moisture gauge and try to let it dry a little between waterings, and try to keep it in the "good" portion marked on the middle of the gauge for a day or two. I water from the bottom by filling the tray. Seeds are started in 4" pots. I have a couple fans that circulate air over the seedlings. I have measured light output under my led grow lights at about 80,000 lux at leaf level. The seedlings do not appear leggy. Sometimes they will bloom tiny blooms far ahead of schedule (I have some 6 week old tomatillos that have little 0.5inch blooms right now) and the leaves are usually small. Sometimes they recover when I move them outdoors to start hardening off. What could I check or what could I be doing wrong that causes my seedlings to struggle so much? I'd really like to be able to start my own seeds indoors as I want to try varieties that need a longer growing season or are not normally available as starts from garden centers.
Adams County Colorado
Expert Response
John,
There could be many things at play here. Watering from the bottom is typically most helpful when growing seeds into seedlings. Top watering once emerged should be fine.
You could try a different seedling soil in future. If your seedings are getting root-bound it may be time to pot up into a larger container. Starting in small containers is better so the soil moisture doesn't overwhelm the seedling or develop into root rot.
Discoloration is usually a nutrient issue (yellow - nitrogen, purple - phosphorus). Once seedlings have emerged and the first few true leaves are out you can use a weak balanced fertilizer with watering or every couple of weeks.
Early flowering is also a sign of stress which could be due to watering, nutrients, or light. You could try raising your light a little since the plants are quite compact.
It can take trial and effort to get seedling starts going well indoors for sure!
Happy to answer additional questions you may have.
There could be many things at play here. Watering from the bottom is typically most helpful when growing seeds into seedlings. Top watering once emerged should be fine.
You could try a different seedling soil in future. If your seedings are getting root-bound it may be time to pot up into a larger container. Starting in small containers is better so the soil moisture doesn't overwhelm the seedling or develop into root rot.
Discoloration is usually a nutrient issue (yellow - nitrogen, purple - phosphorus). Once seedlings have emerged and the first few true leaves are out you can use a weak balanced fertilizer with watering or every couple of weeks.
Early flowering is also a sign of stress which could be due to watering, nutrients, or light. You could try raising your light a little since the plants are quite compact.
It can take trial and effort to get seedling starts going well indoors for sure!
Happy to answer additional questions you may have.
