In colder weather, greens can be harvested in the afternoon, tied, washed, placed in buckets and held outdoors overnight. Otherwise, they need to be cooled to 32 degrees F with a humidity of 95 to 100 percent. Under these conditions collards can be stored for 10 to 14 days and kale and for 2 to 3 weeks. Physiological Disorders Tipburn causes the leaf-margins to become necrotic and is more serious on cabbage than on other crucifers. This is a calcium-related disorder but symptoms are usually not relieved by spraying with calcium.
Calcium requires root pressure to move into the leaves, especially the inner leaves of the head.
Where humidity or soil water is low, root pressure will also be low. Sometimes on flooded soil, root pressure can also be low because root function is impeded. Another factor that can cause tipburn is fluctuating growth rates, especially very rapid growth rates. Reducing nitrogen rates, early harvesting and close spacing can lower tipburn damage caused by rapid growth rates.