Sefer Ha’mitzvos Ha’Katzar (The concise book of mitzvos) By the Chofetz Chaim

This book lists the Torah mitzvos that can be observed today

Second Section – the Negative Commandments

107. It is a negative commandment “do not plant two different types of seeds in a field”

As it states in Vayikra (Leviticus) 19:19, “in your field, you should not plant Kilayim (two different types of seeds).” Outside of the Land of Israel, it is permitted to initially plant Kilayim. A mixture of two trees, which is grafting an esrog tree with an apple tree or anything similar, is forbidden outside the Land of Israel. It is also forbidden to graft a tree with a plant or a plant with a tree, even outside the Land of Israel. If two species were mixed in plants or trees, even though a negative commandment was transgressed, the fruits are allowed to be eaten, even by the person who committed the sin. Mixed species of a vineyard (which is planting grain in a vineyard), is forbidden to plant. Eating and deriving pleasure from mixed species of a vineyard is forbidden according to the law of the Sages outside of the Land of Israel. It is forbidden in the Land of Israel according to Torah law.