Does the prohibition of kilei zera'im apply to flowers?

Answer

 Excellent question! (All of the above are!). While the rule of thumb is that the kilei zera'im prohibition applies to annuals worthy of human consumption, there is a less-known halachah that the prohibition applies also to all plants that are sown in entire fields, such as cotton.

Since flowers are grown commercially today, they should also be distanced from edible annuals (12 cm), but need not be distanced one from another.

Note: This is a chiddush by Rabbi Shaul Yisraeli, whose rulings we follow at Torah VeHa'aretz Institute.

The Chazon Ish was lenient and does not require distancing.