In early planting situations, the seed is vulnerable to a number of threats because it begins to germinate and emerge too soon, under less than optimum growing conditions. The seed can be subject to fungal pressure and can often result in an unhealthy plant with poor vigor and poor uniformity to the other plants.
Furthermore, the cold weather will slow the emergence and early growth process, thereby extending this period of vulnerability. In fact, emergence can be delayed by two, three or even four weeks compared to the normal rate of five to seven days.
During this prolonged emergence period, seeds may experience extremely cold temperatures, making them more susceptible to chilling injury, which weakens their metabolism and stunts their growth.
A lengthy germination process also means the seeds can deplete their own internal food reserves. If seedling roots are not sufficiently established to extract nutrients from the soil or leaves are not sufficiently developed to carry on photosynthesis, this depletion can weaken the seedlings. The resulting plant stands following such chilling injury and/or will be poor - perhaps so poor as to warrant replanting.
