Common causes of failure are soil too heavy, wet or cold, or allowed to dry out, not giving slow seeds long enough to come up, pests eating the seeds or seedlings, and not giving dormant seeds the proper pretreatment. Careful attention to the instructions in the catalog and on the packet will help insure good results. Plants from temperate regions, the arctic, high mountains and high deserts often germinate best at cool temperatures. Plants from winter-rain areas like California, the Mediterranean, Chile, S. Africa and parts of Australia also like cool temperatures. Warm desert plants and tropicals like warmth.
Time varies with temperature, so expect considerable variation.
These will stand some frost and can be sown direct to the garden as early as the ground can be worked, March to June. Prepare the soil until a smooth, fine surface is obtained. An attractive annual border can be had by planting in large, irregular drifts. These are killed by frost and should be sown in late spring after danger of frost. These need warmth and shelter and are best started in pots or flats and planted out in favored spots after the soil has warmed.