He sold trees and retained the land - מכר אילנות ושייר קרקע
Summary:
The רשב"ם maintains that the מחלוקת between רבנן ור"ע is by two אילנות and ר"ע maintains that even if קנה אילן א he is קנה קרקע. However תוספות maintains that all agree that by less than three trees he is not קונה קרקע, and the מחלוקת is by three trees where the seller explicitly stated that he is שייר (כל) הקרקע.
Summary:
One may plant seeds within ד' אמות (but outside ג' טפחים) of a כרם whose rows are separated by less than ד' אמות, and such a כרם does not exempt him from battle.