christmas cactus (starting from shelybear's correction):
The flowers, which are often shaped zygomorphous, are available in different colors.
The flowers, which are often shaped zygomorphously, are available in different colors.
or possibly:
The flowers, which are often shaped zygomorphous, are available in different colors.
The flowers are often zygomorphous and are available in different colors.
spring snowflake (again from shelybear's correction):
In phenology its flowering shows the beginning of spring.
In phenology its flowering heralds the beginning of spring. (optional comma after phenology, and of course heralds is just a stylistic thing)
and myon, the pumpkin correction is slightly off; it could be
The whole plant is roughly haired, which protects the seedlings from natural enemies.
or omit the comma from your original correction:
The whole plant is roughly haired to protect the seedlings from natural enemies.