The system allows you to associate two different salesperson to the same customer based on the category divisions: Fresh Cut Flowers and Plants.Here are the instructions to do so:
Go to Setup > Customers and search for the customer you wish set.
Under the "Actions" column click on "Edit"
On the customer information you'll find both options: "Salesperson for Flowers" and "Salesperson for Plants". Select the the account manager that will be linked to each division and save.
This setting will affect Standing Orders, Prebooks and Invoices.