Select fresh, crisp, healthy greens with good color and no blemishes. Cut off particularly large, woody stems as they don't freeze well. Rinse them several times under cold running water. Chop the leaves and stems to the desired size (small leaves can be frozen whole).
Fill a large bowl with ice water.Bring a large pot of water to a boil. Place the greens in the pot and cover with the lid. Don't overcrowd the greens, it's best to work in batches. You'll need about 1 gallon of water for every 4 cups of greens. Most greens require 2 minutes of blanching except for collard greens which need 3 minutes and baby spinach which needs 90 seconds.
Immediately after the allotted blanching time, drain the greens and plunge them into the ice water. Let them cool for the same amount of time as blanching. Drain them well and then squeeze as much water out of them as you can.Place the prepared greens in freezing containers or in ziplock bags. Squeeze as much air out of the bags as you can. Label and date the bags and place them in your freezer.Properly prepared, leafy greens will keep for 8 to 12 months in the freezer.