From the Ground Up Blog

How to Care for Seedlings and Preventing Damping Off

How to Care for Seedlings and Preventing Damping Off

When starting your garden, one of the most exciting moments is when the seedlings you planted start to grow. But while your plants are in the seedling stage, they are very sensitive and susceptible to disease, so it’s important that you care for them properly to ensure they’ll continue to grow once transplanted in their final garden bed.

How to Care for Your Seedlings

Monitor soil moisture and water as needed to maintain even moisture; soil should not be soaking wet or extremely dry. Allow the soil to dry slightly between waterings to encourage strong root growth. If algae growth appears on the soil surface, reduce frequency of watering.

Many seed starting mixes contain only small amounts of soil nutrients. When seedlings reach a few inches tall and have developed true leaves, it is a good time to fertilize them with a low-strength water-soluble fertilizer. For many vegetable and flower species, you can fertilize your seedlings once per week.

Correcting Common Seedling Issues

If your seedlings germinate and emerge but do not grow past a few inches tall, review their growing conditions to make sure they’re getting all that they need to continue to grow. Newly emerged seedlings prefer bright overhead light, warm temperatures, and even moisture. 

Grow Lights For Seedlings

More: How to Water Seedlings>

If your seedlings are thin and weak, provide supplemental light or adjust lighting so that it is directly above the seedlings. 

If you are growing your seedlings in germination trays, remove any tray covers that may be covering them. 

Transplanting Your Seedlings

Healthy seedlings can outgrow germination cell trays quickly. If the soil is drying down quickly and the seedlings seem to be growing more slowly, it may be time to transplant them into a larger container. 

A seedling that has outgrown its cell will have dense white roots easily visible when lifted from the cell tray or sometimes growing through the bottom of the tray. Transplant these root-bound seedlings to a larger container or to their final garden bed as soon as possible to reduce stress and prevent stunting.

Damping Off: The Seedling Killer

Damping Off

If seedlings emerge and die shortly after or they reach a few inches tall and then die, it is possible they were killed by Damping off, a seedling disease. Damping off occurs when seedlings are overwatered and a fungus or mold infects the trays, killing the vulnerable seedlings. The smaller the seedling is, the more susceptible it will be to the disease.

Symptoms of Damping off include:

  • Seedlings do not emerge from the soil.
  • Seedling stems and cotyledons are water-soaked, mushy, and discolored.
  • Young leaves wilt and turn gray to brown.
  • Roots are absent, stunted, or discolored.
  • White mold is visible on infected plant parts or soil.

Damping off is caused by a fungus or mold (often Fusarium spp., Rhizoctonia spp. or Pythium spp.) that thrives in cool, wet conditions and can be easily spread by contaminated tools, pots, trays, and potting soil, or by irrigation splash or certain insects, like fungus gnats. 

It is common for Damping off to kill large sections or whole trays of seedlings, or to cause root or crown rot in more mature plants.

Preventing Damping Off in Your Seedlings

To prevent Damping off follow these steps:

  1. Sterilize all used pots, trays, and tools with a solution of 10% bleach prior to use. This prevents cross-contamination and gives you a fresh start when you plant your seedlings. 
  2. Use new potting soil for starting seedlings. Do not re-use soil or use garden soil or compost. Seedlings are sensitive and need fresh soil with low-strength, water-soluble fertilizer.
  3. Avoid overwatering your seedlings, and choose pots and trays with good drainage holes.
  4. Keep soil temperatures warm with a heat mat, and water seedlings with clean, warm water.
  5. Keep seedlings healthy by providing bright overhead light, warm temperatures, and proper soil moisture.

Caring for Your Seedlings

It can be devastating if the seedlings you care for do not make it to your garden due to improper maintenance or damping off. However, as with all plants, your seedlings will thrive and become fruitful with the proper care.

If you’re looking to start your seeds, we recommend these seed starting supplies, and if you run into any issues along the way, we’ll be happy to help answer any questions you might have. 

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