Unfortunately, there are a few disadvantages to direct-seeding. The obvious problem is the plants will not be flowering as soon in the garden as compared with those started indoors and set out as transplants. Also, after the seedlings come up, they will need to be thinned out to a uniform plant spacing. The seed bed should be worked well and raked so that the soil is fine, without large clumps or clods. Direct-seed annual flowers after the threat of frost is past in the spring and when the soil warms ups.
Some species germinate faster if the seeds are given a special treatment prior to planting.
Morning glories, for example, will germinate faster and more uniformly if the seed coat is nicked slightly. This can be done using a nail clipper to snip off a small piece of the seed coat on one end. Scarify sweet pea seeds by filing the seed coat on one side. After scarifying the seeds, soak them in warm water for 24 hours before sowing. Sow the seeds in shallow furrows then cover them lightly with fine soil.