This kind of "killing frost" has a strong impact during below-freezing temperatures, particularly at the beginning of the growing season, when plants have lost the physiological protection against freezing that protects them.
(This kind of "killing frost; has; a strong impact during below-freezing temperatures, particularly at the beginning of the growing season) (plants; have lost; the physiological protection against freezing) (freezing; protects; them)
This kind of "killing frost plants freezing
has have lost protects
a strong impact during below-freezing temperatures, particularly at the beginning of the growing season
the physiological protection against freezing
them