Soil moisture conditions and seedling survival are generally better in spring than during any other season. Light conditions are generally best for growing at one-half full sunlight. Beyond the seedling stage, giant sequoia unhindered by an overstory continues to grow at the same rate as its competitors. Lower branches die fairly readily from shading, but trees less than 100 years old retain most of their dead branches. Low temperatures seem to be the limiting factor for giant sequoia at the upper elevational limits of its range, as well as in areas with severe winters where the species has been introduced.
Giant sequoia is found in a humid climate characterized by dry summers.
Most precipitation comes in the form of snow between October and April. Some groves are on glacial outwash from granite. Other common parent materials include schistose, dioritic and andesitic rocks. Giant sequoia grows best in deep, well-drained sandy loams. It occurs with higher frequency on mesic sites, such as drainage bottoms and meadow edges.