I couldn't tell you how many pictures I've shot of hummingbirds feeding or just sitting on a Zinnia. Young hummingbirds find them incredibly attractive and obviously find some value in them to keep returning. For me they are a "MUST HAVE" in a hummingbird garden.
It is NOT too late to start these attractive flowers. Zinnias develop a large pom pom shaped flower at the end of every stem the plant produces. You can get an array of colors that are incredibly attractive to hummingbirds. They appear like they have no nectar, but the hummingbirds, particularly the young, keep returning because they are getting some kind of nutritional value from them. Zinnias are a drought tolerant annual that do well in most climates, from cool to very hot. They are very fast growers, and this is the reason I mention them today. It is NOT too late to start them.
Plant the Zinnia seeds in their containers and cover them with about 1/4" of soil. Water and watch. In about 5-10 days you will see growth. As soon as they germinate, put them out in direct sun, as long as temperatures are above 5C(42F). Bring them in overnight if temps dip below this as well. As long as they get direct sun right after germination there will be no need to climatize them. Don't over water them as they will get brown at the end of the leaves. Plant them in the garden when there is no more risk of frost.
For those well into the season, south of me, don't think you are too late in starting them from seed. If it's not too late in my region, it's definitely not too late in yours.
Juvenile Male Ruby-throat hummingbird. N.E. of Edmonton, Alberta, Canada. July 28, 2018.