Cucumbers should be started indoors about 4-5 weeks before they are ready to go out into warm soil and warm temperatures. I recommend planting 2-3 seeds in larger containers and thinning them two to plants per cell. The key is getting them into warm soil. They are warm weather crops.
New to Gardening? Check out my 2nd Gardening YouTube Channel dedicated to New Gardeners. The videos are longer and more detailed. Each video presents as if you are new to gardening.
Join My Google+ Gardening Community called Our Tomato & Vegetable Gardens – we are approaching 5000 world-wide gardeners: or Link from My YouTube Page.