your bed is 4ft 10 inch squared you can easily get 10-12 per row and 7 rows in i put 5 plants in a 2ft by 10in trough and mine have always done well i have 125 plants with around 1500 flowers on them but when the runners come i put a plant pot at the side and peg runner in there not in the trough, as i only allow 5 in the trough. strawberrys can manage a little cramping there packed tightly when you go strawberry picking and you can never have enough strawberry plants. Blackmore do strawberry plants at good prices £5 for 10 cambridge favourite runners, good quality too as i had 60 strawberry plants of them and all have servived.