My poor seedlings need sunlight! Last week, we enjoyed temperatures in the 70s and plenty of sunshine. Today, it is snowing. The flats of seedlings have been on the kitchen table for four days and they’re showing signs of stress. I thought it was a good opportunity to talk about troubleshooting seedling failing before they harm your plants.

University of Minnesota- Troubleshooting Seedling Issues 

Brown or Yellow Leaf Tips

After setting the plants in the greenhouse last week during those beautiful days, several of the plants, especially the tomatoes, exhibited brown tips on their leaves. Too much of a good thing can be a bit much, and they were burned a smidge.

Seedlings Failing Suddenly

If most or all of your plants die suddenly, especially if they tip over at the base of the soil, it’s probably damping off, a fungal disease. There is nothing you can do once they are dead, but you can prevent the infection by using a sterile potting medium. You also don’t want to overwater the plants because it can perpetuate the infection.

Seedlings’ Leaves Suddenly Droop

If seedlings droop but don’t die outright, overwatering is a likely cause. Always have adequate drainage holes in the bottom of your containers, whether planting directly in a plastic flat or recycling a yogurt container. Water and allow it to drain through the bottom. Don’t water again until the top of the soil is dry to the touch.

Reddish Leaves and Stunted Growth

Plants obviously can’t speak, but you can often use clues from your plants to understand what they need. If your seedlings’ leaves turn a purple or reddish color, the first thought should be a phosphorus deficiency. This might be because they do not have enough in the soil, but it can also be if the temperature is too cool and the plants cannot utilize the available phosphorus.

If your plants are in a cool location, try moving them to a warmer area or placing a heat mat underneath them. It also won’t hurt to apply a balanced fertilizer.

Curled — Even Crumbly — Leaves

There can be several reasons why the seedlings’ leaves become curled and sometimes crumbly. Excessive direct sunlight is one reason. Drying out is another, particularly if the planting medium drains rapidly.

This usually doesn’t happen if your plants are indoors and under grow lights, but sometimes, it’ll occur when they are set outside in a cold frame or greenhouse. Even in the spring, a 70+ degree, sunny day can scorch plants. Use a shade cloth or floating row cover to diffuse the sunlight and reduce evaporation.

Long and Leggy Plants

Seeing the seedlings stretch to the point where they barely remain upright is a common problem caused by the lack of light. With indoor lights, drop them so they’re 2-4 inches above the plants.

If you’re not using lights, keep them in the sunniest windows of the house. This might mean rotating them from window to window, particularly early in the season, to provide enough light.

Troubleshooting Your Seedling Problems

A few of my plants are looking a little leggy at the moment after spending several days indoors where it’s warm but not very light. Thankfully, the forecast calls for sunshine tomorrow, so hopefully, they’ll be much happier in a day or so.