However, some need to started in January and February if you want them to bloom this summer. Most usually bloom within 6-12 weeks, hence sowing them in March and April and can be sown out in the garden hopefully with fingers crossed by the end of May in these parts of the great North.
Not all annuals are actually true annuals. Some are tropical perennials that we treat as annuals. Spring bulbs act the same way like my favorite dahlia. It is a zone 8-10 and would no way life here without lifting them in the fall.
Some do not always want to bloom the first year, so to insure that they do you need to start them in January or February to give them at least a 5 month heads up on bloom time.
There is also quite a few factors involved in starting our seedling and the major one being light. Sometimes mother nature is not always there for you this time of year so we rely on grow lights. Fluorescent lighting will also do fine providing they are cool white. They need to be set about 6" above the seed trays and moved up as the seedling begin to grow. Using a timer is also a great way to ensure they are getting the needed light.
So what are one of those annuals you ask. Begonias. One of the most popular begonias now is the Tuberous Begonia. The Nonstop Series of multiflora begonias are smaller but have numerous blooms and are quite expensive if bought at your local nursery. However, the seed is not cheap either, but spending $15-$20 in seed can give you hundreds of dollars of annuals if you were to buy them. Your gardens will be exploding with massive planting.
They are rather slow at starting and putting them in the pots is rather a challenge too. The seed is so tiny, you can barely see them with the naked eye. These gems need to be started in January. They grow best on the surface and them covered with a plastic dome in a well lit spot at about 24-26 degrees celeius. Becareful though, they start producing tubers then go dormant if they do not get up to 15 hours of light. So after all that you should see green in around 20-25 days.
They like to be warm and well lit and only need watering if the soil is getting dry. After your have reached germination leave the dome on as they like and need the extra humidity. Within a month of germination you can start to see the leaves and this is when it is time for their first transplant.
It is suggested to put a dome over them again for about a week. Fertilizing is recommended with a half strength all purpose soluble fertilizer every 2-3 weeks.
Soon they will need a second transplant and using a 4" pot is best. Once again water only when the soil is dry. Overwatering will most likely rot them. In late May they can start to be hardened off and by June they can be planted out in the garden in partial shade in hot summer areas or full sun in cool areas. Enjoy them for the rest of the summer. It will be well worth it.
Another begonia is the wax begonia. They are a little faster and a little less complicated to grow then the tuberous but equally as small and fragile in the beginning. They can be started in February but prefer longer days of light, up to 18 hours and can be grown a little cooler at 15-18 degrees celeius once they are up. Since they are a smaller plant, transplanting them into a 3" pot is sufficient.
Here are a few other annual that should have a earlier start.
Zonal and Ivy Geraniums