How to Grow Healthy Seedlings

  

Once your seeds have sprouted, there are three factors that will have a strong influence on how well your seedlings grow and develop: light, water and fertilizer. Of these three, adequate lighting is one of the most critical.  Seedlings grow best when they have the right amount of light. Most of the time the light coming through a bright, sunny window isn’t going to be enough for your seedlings. They will tend to stretch and get thin and spindly looking for light. Seedlings need a consistent source of the right light. You have several choices when it comes to selecting a grow light including fluorescent lights (CFLs), high-output T5s and LEDs. T5s are generally considered the best choice for seedling development, especially if space is a consideration; T5s can be placed closer to the seedlings then LEDS.  

Select a T5 in the 6400K spectrum, for best seedling growth. Plan to run your grow lights fourteen to sixteen hours per day. It’s also important that your light setup is adjustable, so that you can raise the lights as your plants grow. When your seedlings are small, place your lights five to six inches above the tops of the plants. As the seedlings grow and develop, move the lights up.  It’s also important to rotate your seedling trays every week.  Next to light, watering is most important. Check your seedlings every day and keep the soil moist, not soggy. Don't use water that is too cold (or too hot). Fill up your watering can and let it set out overnight. That way the water will be at room temperature when you water your seedlings. 

In order to develop strong stems and root structures, your seedlings need to be fed. Begin fertilizing once your plants have 3-4 sets of true leaves. The first set of leaves to emerge are the cotyledons, sometimes referred to as ‘seed leaves”. They are not “true leaves”. The next set of leaves and all subsequent leaves are true leaves.  Use a mild fertilizer such as fish and seaweed 2-3-1 or liquid Kelp. Liquid fertilizers are preferable at this stage, because it’s less likely you’ll damage the seedling’s roots than if you used a granular starter fertilizer. Plan to fertilize your seedlings every two weeks, at a concentration of one teaspoon or five milliliters per gallon of water.  Let your water sit out overnight in order to reach room temperature.  

Brush your starts several times a day. Plants, especially tomatoes need movement in order to develop strong stems. Brushing them a couple of times a day makes them stronger.  Or simply install a small fan and run it 5-10 minutes twice a day.  Doing these things will help ensure your seedlings are strong and healthy when it comes time to move them to your garden.