H S G Low temperature and High temperature.
When H is negative and S positive and G negative there will be spontaneous low temperature and spontaneous high temperature. When H is negative, and S is negative and temperature dependent then the low temperature will be spontaneous and high temperature will be non-spontaneous. When H is positive and S is positive then the temperature dependent and low temperature are non-spontaneous and high temperature will be spontaneous. When H will be positive and S is negative then G will be positive, the low temperature will be non-spontaneous and high temperature will also be non-spontaneous.
Seed plants have an evolutionary advantage for several reasons. For one, the seeds can disperse easily. Furthermore, seeds can time their germination. For example, some seeds only germinate when they experience a period of being frozen.