The spinach season varies each year with weather. Spinach, like most greens, does best in cool damp weather. With the sharp weather changes in spring, there is a time when the plant leaves get thinner and smaller as the plant starts to shift energy from making leaves to producing seed. When growers say bolt, this is what they mean. The plant has shifted its energy, and it is only a matter of time until the seed stalk shoots up and the flavor changes.
When one crop catches 
up to a later planting or the end is in sight, I set aside some spinach to freeze for winter. First I rinse it.
Then I place it briefly in boiling water to blanch it. Blanching arrests the enzyme that ripens and rots food, and preserves that peak freshness.
This is for just a minute or two – until it changes to bright green
Then it goes into cold water to stop the blanching process and preserve as many vitamins as possible.
Next I squeeze out the water.
Then I drain and pack into bags, label, and place in the freezer.
