How do I keep seeds started indoors in seed trays alive?

March 22, 2022 Ask the Expert, Seed Starting and Propagation

Question:

I’ve started seeds indoors in seed trays with plastic covers. I rotate them every other day so that they each get enough light. Many of my seedlings die, I think because the soil is either too wet, or, if I take the covers off, too dry.  How do I keep them alive?

Answer:

Abi Griffith, Horticulture Community Education Assistant

Sorry to hear about your trouble with starting seedlings indoors at home!  I am going to include this fact sheet Starting Seeds at Home as a reference to best practices to help you troubleshoot.
The fact sheet goes through different factors that can affect your seedlings:
  • Substrate and Containers:  Use sterile, well-draining seed starting substrate, containers with drainage holes

  • Temperature: Cold temperatures or inconsistent temperatures can inhibit germination (the fact sheet lists time and ideal temp for certain seeds to germinate)

  • Moisture: This is the factor that goes wrong for so many growers and sounds like a concern for you! Substrate should be kept moist for germination, but not too wet. Once seedlings germinate, the substrate should be allowed to dry between waterings. You should also remove the plastic dome after germination. (I sometimes will put the dome back on overnight to retain moisture and warmth with certain types of newly germinated, heat loving seedlings such as peppers or tomatoes, which you wouldn’t want to start until April anyway, but usually only for it’s very early life). In general, over watering can lead to dampening off, yellowing leaves, stunted growth and seedling mortality. The video in the fact sheet demonstrates how to soak your tender germinated seedlings “from below”, by setting them in a dish of water, to avoid wetting the actual seedling too much.

  • Light: The fact sheet will give you more info on this, but when using lights, make sure they are close enough to your seedlings.