1. Use a pencil to carefully poke three small holes in the bottom of each individual egg cup.
2. Fill each egg carton cup three-quarters full with potting soil. As an option, you can mix used coffee grounds with soil in a ratio of three-quarters soil to one-quarter coffee grounds.  
3. Place a few seeds in each cup, then cover with a thin layer of soil.
4. Place the egg carton on a waterproof plate or tray and set it in a warm, sunny spot inside your house.
5. Spray a small amount of water on the carton every other day, keeping the soil moist but not soaked. If you see water coming out of the bottom of the egg cups, you've used too much!
6. Keep seeds indoors for four to five weeks. Once the seeds sprout and have multiple sets of strong leaves, they can be taken outside.
7. Egg cartons made of paper can be planted directly into the ground because they will biodegrade. Cartons made of Styrofoam will not break down; instead, remove the plants and soil and transplant them into the ground or larger pots. 

What's happening?

For the first few days, you probably didn't see much going on in your garden, but under the soil the seeds were germinating. That means it started using the energy stored as food inside the seed to make its first root and leaves.

After about a week, little green stems should poke up out of the soil. Once the first leaves appear, they capture sunlight to create food, allowing the plant to grow. This is called photosynthesis.

Tips

Some people are allergic to bee stings, so if you are planting bee-friendly flowers in your garden choose an area that's good for bees as well as people.

Vocabulary

Germination
The process by which an organism like a plant grows from a seed

Photosynthesis 
The process used by plants to take energy from sunlight and convert it to chemical energy that is then used to fuel its growth 

Recommended reading

Give Bees a Chance by Bethany Barton

From Seed to Plant by Gail Gibbons