The onion is one of the oldest vegetables, believed to have originated in Asia around 3500 B.C. Onions were popular because they did not spoil in the winter like many other vegetables. The National Cancer Institute says onions contain antioxidants that can help to lower cholesterol and block cancer. Onions grow well in cold weather, which makes them one of the first crops you can plant in the spring in Pennsylvania.
Work the soil once the frost leaves the ground, usually sometime in March in Pennsylvania. Mix animal manure and compost into the soil to make a rich, loamy soil mix.
Decide if you are aiming for green onions or larger, dry onion bulbs. If your desire is to harvest green onions, you can plant them closer together than if you are growing onions large.
Make a trench 1-inch deep in your garden where an onion row will be. The handle of your garden rake makes an effective tool for scouring out a planting trench. Space rows 12 to 18 inches apart.
Lay your onion sets in the trench so that they are touching if you are looking to harvest green onions. Space them 2 to 4 inches apart if you are growing them into large onions.
Close the trench by raking the soil over the onion sets. Tamp it down with the rake.
Water them in thoroughly until the soil is moist to remove any air pockets and also to ensure adequate soil contact.