I have a small north facing balcony in the nw suburbs y in zone 5 a and have been trying to grow plants last 3 yrs but not very successful, finally i am able to get tomatoes to grow in the 10 gallon pot in the pic, i have this nice size planter where i would like to grow 2-3 varieties of vegetables,I tried beans, strawberry,pepper, they grew ok but gave a very small yield last summer like 10 may be.
I need help in following areas
1) which plants can i combine both for display of flowers and vegetables
2) can i use a trash bag liner iwth holes for the planter box , why is the planter box always dry during summer , i am watering everyday and also change miracle gro mix every yr
3) what plants to use in hanging planters and on the rails, other than petunias? i combined petunia and strawberry, no sign of strawberries last yr but petunia grew well.
4) how many plants can be combined in hanging planters or window boxes and large planters?

I am very bad at planning, i buy plants at sale and ones that will grow well and needs less care and try to combine 3-4 plants in one container, why are my plants not growing at all ?