To harvest field greens, simply snip off leaves of dandelion and nettles (I often use the entire top portion when they are less than 6 inches in height). For chickweed and purslane, snip off stems and leaves, both are soft and edible. Filled with nutrients and rich chlorophyll, these foods can satisfy your body’s craving for fresh, wholesome foods right from your yard. You do have to be careful to only harvest from areas that you know have not been treated with any chemicals. Be aware that many towns spray alongside of roads, and even if they have not done so this early in the year, there may be residual chemical buildup from previous applications. So, it is best to find an area off the beaten path, or your own yard.
Related journals to harvesting field greens:
Journal of Ecology and Environmental Sciences, Journal of Biofertilizers & Biopesticides, Journal of Harvesting collard greens, Journal of Agriculture & Life Sciences, Journal of Effect of pre-harvest application of gibberellic acid
Advances in Recycling & Waste Management received 438 citations as per Google Scholar report