How can you distinguish them?
The following article is from my book, How to treat yourself at home without medicine.
2.1.2 Yin and Yang (Food)
vegetables which grow into the ground have more Yang energy,
and Yin is centrifugal, so
vegetables which grow toward the sky have more Yin energy.
That is why root vegetables have more Yang energy. If we need to warm the body, we need to eat more root vegetables.
On the contrary, in the summer, we eat summer vegetables which have more Yin energy such as tomato, eggplant, cucumber, etc., because they are good to cool down the body.
However, if we take too much summer vegetables, the body becomes cold. In Japan, there is an old proverb that you must not let your daughter-in-law eat eggplant, because they want to see grandchildren as soon as possible, but an eggplant is a strong Yin vegetable, so it makes their daughter-in-law’s body cold, causing various gynecological diseases, especially infertility, miscarriage, etc.