Sprouting Made Easy: Start Your Seeds in Egg Cartons

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When you plant 30,000 strawberry plants in anticipation of a big spring event like we do at Barton Hill Farms, you start thinking about planting very early. 

But for those of you who are growing on a slightly smaller scale, the time to think about seedlings is now. 

By germinating seeds and establishing your sprouts in the winter, you’ll have proud little plant babies to get in the ground as soon as the chance of frost has passed. 

Most people don’t have a dozen or more little pots hanging around where they can get their plants started. But you have another vessel at home that is perfect for seed starting — egg cartons!

Why egg cartons?

They’re perfect for the job! Egg cartons are already divided into perfect little cups, ready for a bit of potting soil. Plus, with their long narrow shape, they’re the perfect size to rest on a sunny window sill where they’ll soak up the rays without getting too cold.

Plus, we’re all about reducing our waste and making our goods do double duty. And there’s no better way to do a little cheap gardening than by repurposing things you already have.

How to start seeds in egg cartons

1. Prepare your cartons

First, you’ll need to collect your egg cartons. If you don’t have enough, ask your neighbors if they have any they’d be willing to give you.

Once you’ve collected your cartons, they need a bit of prep. Drainage is important to prevent water from collecting and rotting the seed or roots. So poke a few small drainage holes in the bottom of each cup. You can cut the lids off of the cartons and place them underneath the seed cups to catch any water.

Sporuting Seeds

2. Plant your seeds

Next, fill the cups about half-way with a seed starting mix. This is a very light soil-less blend that won’t weigh down sprouts. It’s effective, but it’s also a bit more expensive than potting soil. To save a bit, you can mix three parts potting soil with one part perlite, an ultra-light volcanic glass that will reduce the density of your soil. 

Drop two or three seeds in each individual egg cup, since not all of them will germinate. Then cover them with seed starting mix or potting mix. Check the seed packet to make sure you don’t plant them too deep. The packet will tell you how thick the soil layer on top should be.

3. Walking on eggshells…

Another green option is to recycle not just the cartons, but the eggshells too!

The basic method is the same, but instead of filling your carton with soil and seeds, you’ll fill an eggshell that will sit inside the carton. Shells are made from calcium carbonate, an important nutrient for growing plants, and they make a great eggshell pot. 

4. Give ’em a drink

Water the egg cups well. Keep the soil moist but not soaking while they work their underground magic. If your house is cool, you may also want to put them in a plastic bag to keep them nice and warm. Check on them daily and water frequently.

Sprouting Seeds from Egg Cartons

5. Wrap up warm

The most important part of germinating seeds is to keep them warm. Soil needs to maintain a minimum temperature of 70°F. You could place a warming mat under your seeds, or put them in a warm area of your home like on top of the refrigerator. Once they reach about a half-inch tall, move them to a sunny spot.

Transplanting your seedlings

Timing is vital when it comes to transplanting your seedlings. First, all threat of frost must be passed. But you also can’t leave your seedlings in their egg cartons for too long, waiting for the weather to heat up. 

Seedlings should be moved to the garden once the roots reach the bottom of the tray, but before they start to grow into a circle. Circling roots will make your plants unstable and stifle their growth. So time your seedlings carefully to ensure the weather is warm when the seedlings are transplant-ready! 

The way you transfer your sprouts to the garden this will depend a bit on the type of egg carton you used. If you used a cardboard egg carton, you can cut the cups apart and plant the whole cup right in the soil! The cardboard will disintegrate and return back to the ground. If you go this route, it’s a good idea to cut some slits in the cardboard cup to make it easier for the roots to expand as the plant grows.

You can also plant the whole eggshell “pot” in the ground to give the young plants the benefit of that extra calcium carbonate.

If you used a styrofoam or plastic carton, you’ll have to remove the plant and its soil from the cup before planting. Poke your finger down the side of the cup, and lift out the seeding and its roots with as much of the soil as possible. Place it into a hole in the garden, and cover gently with more soil. Water thoroughly!

There you have it! 

Egg carton gardening is an easy way to start vegetables, flowers, and herbs like oregano, thyme, or parsley. With simple materials that you already have in the kitchen, you can try this cheap gardening experiment with the kids to get them excited about your spring garden!