Make sure you are in the applicable season. When you create a new cultivar, the cultivar will be created only for the season you are currently in.
The current season is selected in the top right corner of the page.
Go to the Settings page by clicking on "Settings" in the sidebar navigation.
Select the "Cultivars" block. You will be redirected to the list of cultivars.
Click the "Create Cultivar" button located at the top right of the page.
Put in the name of the Cultivar, the Season will be autoselected as the season you are currently in, and select the type of Crop of which this Cultivar is.
Click on "Create Cultivar" to save the new cultivar under the season you are in.