Caring for Seedlings

A few days after you start your seeds indoors, you might have a few seeds beginning to sprout. As exciting as it is to watch your seedlings come up, it’s also a very precarious time in your plants’ development. You’ll need to care for your seedlings diligently in the coming weeks so that they grow into strong and healthy plants.  ​

Image by Alina Kupstova (unmodified)

Once your seeds start to come up, crack the lid of your mini greenhouse and keep it open at all times. When the seedlings get taller, remove the lid completely. Continue to water your seedlings from the bottom every few days.  

Providing enough water for your seedlings is important, but the most important thing that your seedlings need is plenty of light. Ideally, your seedlings need 12-16 hours of bright light a day.
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A good place to start is to position your seedlings next to the sunniest window in your home. If possible, place them in an eastern-facing window in the morning and a southern-facing window in the afternoon. Seedlings bend toward the sun. You should rotate your trays each day to keep your seedlings from growing too far to one side. 

​Unfortunately, skies in North America are frequently overcast in early spring and rarely provide enough sunlight for seedlings even when sunny. For this reason, you will likely need to provide your seedlings with additional artificial light.  

​While you can purchase grow lights specifically made for starting seeds indoors, it is also possible to grow seedlings with ordinary light bulbs using lamps you already have. Fluorescent tube lamps are the absolute best for this because they emit a good amount of blue light, which plants need. If you have some of these lamps, find a way to position them so that you can adjust their height as your seedlings get taller. The light bulbs should be located directly above and fairly close to the seedlings.  

Compact fluorescent light bulbs (the swirly kind) also work well. If you have one, attach it to a lamp that will get the light bulb as close as possible to the seedlings, preferably an adjustable lamp.  

Whatever kind of light bulb you use, you want to make sure it emits some blue and some red light.  If seedlings get too much red light, they grow weak. For this reason, warm-glow incandescent light bulbs don’t work quite as well for starting seeds, since they emit more red light. They also use more electricity and get quite hot, which can dry your seedlings out. They can be used in a pinch, though. Just make sure not to place the light bulb so close to your seedlings that they wilt.  

“What happens if my seedlings don’t get enough light?” Seedlings instinctively stretch towards the light. If the closest source of light is dim and far away, like early spring sun, your seedlings will stretch out and develop thin, weak stems. These are called leggy seedlings. Instead of growing strong and upright, they flop over, which makes them more prone to infection.  

Some leggy seedlings :(

The best way to prevent leggy seedlings is to provide your plants with enough light right from the time they sprout. However, if your seedlings get a little leggy, all is not lost. You can try to strengthen your seedlings by running a gentle fan or brushing your hand over them a few times a day. This simulates the wind outside and encourages seedlings to grow tougher stems.  

Fun fact: the first set of leaves on your seedlings are called cotyledons (ka-tuh-lee-duns)! The second set are true leaves. Once the true leaves are a good size, it is time to fertilize your seedlings with a liquid fertilizer such as kelp extract. Dilute the fertilizer in water according to the instructions – you will damage your seedlings if the solution is too strong! Water the seedlings with the solution from the bottom, as usual.  

True leaves starting to come in on tomato seedlings

If you can’t obtain store-bought liquid fertilizer, you can make your own! Put some cut up banana peels, grass clippings, eggshells, and 5 tablespoons of wood ash (if you have it) in a jar or bucket and cover with water. Let the concoction steep for at least 3 days in a warm or sunny location. This "tea" will provide your plants with the soluble nutrients (phosphorous, potassium, and nitrogen) that they need. Strain and dilute the "tea" before watering your seedlings with it. 

Homemade fertilizer steeping 

If one of your seedlings grows too big for its pot (with roots coming out of the drainage hole), transplant it into a bigger container.  

Keep the seedlings indoors for now! They will need to be hardened off before being transplanted outside.

If you haven’t already, now is a good time to begin to prepare a gardening bed by covering an area of land with newspapers (see Where to Grow) and letting it sit for several weeks while your seedlings are growing.  The next few posts will cover some other things you can do to prepare to garden while your seedlings are growing. 

As always, if you have any questions or tips to share, please comment below!