Practical research from Utah State University for those who grow a fall crop of vegetables either in the garden or in cold frames
Researchers Benjamin Hudson and Dan Drost grew spinach and lambs-quarters in high-tunnels (a tall cold frame) and found that covering with a frost protector such as Remay, significantly increased yields over non-protected crops while actually heating the soil didn’t create any increase in harvest
Bottom line — use a frost protector fabric in the fall or even inside greenhouses or small high tunnels like the one below to increase the harvest of edible green crops in the fall.
Here’s An Important Point For Home Gardeners About The Early Spring Crop
A second trial was done with very early spring crops and the spacing was altered. With this early crop (not with later crops) the harvest increased by moving the plants to a closer spacing (yields up by as much as 48%) from the normal 6-inch spacing to a tight 2 or 4-inch spacing
Bottom line — crowd your early crop or greens and you can harvest leafy greens earlier in the spring growing season.
Do NOT do this during the regular growing season as the increase in leaf diseases from crowding (leaf diseases are more prevalent during warmer weather) will reduce harvests instead of increase them.