Plant later. You are better off with 2-3 five foot plants than 1 ten foot plant. No need for an early start. If they are sitting around waiting to go into flower it’s waiting for pests. It is not too late to put them out right up to the solstice.
Vary the crop, even if you find a reliable strain. What I mean is use 3-4 reliable strains for your area. They do not all always work out due to minor variations in weather year to year. Or pests pressure. 
Don’t try pure sativas outdoor ( except Durban poison) if you are north and have cold winters. They will not start flowering until late September and will not finish until thanksgiving or Christmas. Always pick a hybrid that leans sativa if you want to try them because you like the racy smoke.
Try some autos. This was literally what they were meant for. Not tents when you can put them outside.
Biochar. Char char char. It’s a song I like to sing. Char it baby.
Herbs. All the beneficial insects we like come for the herb flowers. Birds too. If you have space plant an herb garden. Rosmary, sage, thyme, mint (in pot), basil, parsley, oregano, and dill. Since we are talking outdoor.
Make sure you can clone. Incase you find your perfect strain for your microclimate.